persistor

.gitignore

@@ -1,5 +1,4 @@
 tantivy.iml
-proptest-regressions
 *.swp
 target
 target/debug
@@ -12,4 +11,3 @@ cpp/simdcomp/bitpackingbenchmark
 *.bk
 .idea
 trace.dat
-cargo-timing*

CHANGELOG.md

@@ -1,58 +1,3 @@
-Tantivy 0.14.0
-=========================
-- Remove dependency to atomicwrites #833 .Implemented by @pmasurel upon suggestion and research from @asafigan). 
-- Migrated tantivy error from the now deprecated `failure` crate to `thiserror` #760. (@hirevo)
-- API Change. Accessing the typed value off a `Schema::Value` now returns an Option instead of panicking if the type does not match. 
-- Large API Change in the Directory API. Tantivy used to assume that all files could be somehow memory mapped. After this change, Directory return a `FileSlice` that can be reduced and eventually read into an `OwnedBytes` object. Long and blocking io operation are still required by they do not span over the entire file.
-- Added support for Brotli compression in the DocStore. (@ppodolsky)
-- Added helper for building intersections and unions in BooleanQuery (@guilload)
-- Bugfix in `Query::explain`
-- Removed dependency on `notify` #924. Replaced with `FileWatcher` struct that polls meta file every 500ms in background thread. (@halvorboe @guilload)
-- Added `FilterCollector`, which wraps another collector and filters docs using a predicate over a fast field (@barrotsteindev)
-- Simplified the encoding of the skip reader struct. BlockWAND max tf is now encoded over a single byte. (@pmasurel)
-- `FilterCollector` now supports all Fast Field value types (@barrotsteindev)
-
-This version breaks compatibility and requires users to reindex everything.
-
-Tantivy 0.13.2
-===================
-Bugfix. Acquiring a facet reader on a segment that does not contain any 
-doc with this facet returns `None`. (#896)
-
-Tantivy 0.13.1
-===================
-Made `Query` and `Collector` `Send + Sync`.
-Updated misc dependency versions.
-
-Tantivy 0.13.0
-======================
-Tantivy 0.13 introduce a change in the index format that will require
-you to reindex your index (BlockWAND information are added in the skiplist). 
-The index size increase is minor as this information is only added for
-full blocks.
-If you have a massive index for which reindexing is not an option, please contact me
-so that we can discuss possible solutions.
-
-- Bugfix in `FuzzyTermQuery` not matching terms by prefix when it should (@Peachball)
-- Relaxed constraints on the custom/tweak score functions. At the segment level, they can be mut, and they are not required to be Sync + Send.
-- `MMapDirectory::open` does not return a `Result` anymore.
-- Change in the DocSet and Scorer API. (@fulmicoton). 
-A freshly created DocSet point directly to their first doc. A sentinel value called TERMINATED marks the end of a DocSet.
-`.advance()` returns the new DocId. `Scorer::skip(target)` has been replaced by `Scorer::seek(target)` and returns the resulting DocId.
-As a result, iterating through DocSet now looks as follows
-```rust
-let mut doc = docset.doc();
-while doc != TERMINATED {
-   // ...
-   doc = docset.advance();
-}
-```
-The change made it possible to greatly simplify a lot of the docset's code.
-- Misc internal optimization and introduction of the `Scorer::for_each_pruning` function. (@fulmicoton)
-- Added an offset option to the Top(.*)Collectors. (@robyoung)
-- Added Block WAND. Performance on TOP-K on term-unions should be greatly increased. (@fulmicoton, and special thanks 
-to the PISA team for answering all my questions!)
-
 Tantivy 0.12.0
 ======================
 - Removing static dispatch in tokenizers for simplicity. (#762)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy"
-version = "0.14.0-dev"
+version = "0.12.0"
 authors = ["Paul Masurel <paul.masurel@gmail.com>"]
 license = "MIT"
 categories = ["database-implementations", "data-structures"]
@@ -13,55 +13,54 @@ keywords = ["search", "information", "retrieval"]
 edition = "2018"
 
 [dependencies]
-base64 = "0.13"
+base64 = "0.12.0"
-byteorder = "1"
+byteorder = "1.0"
-crc32fast = "1"
+crc32fast = "1.2.0"
-once_cell = "1"
+once_cell = "1.0"
-regex ={version = "1", default-features = false, features = ["std"]}
+regex ={version = "1.3.0", default-features = false, features = ["std"]}
-tantivy-fst = "0.3"
+tantivy-fst = "0.2.1"
 memmap = {version = "0.7", optional=true}
-lz4 = {version="1", optional=true}
+lz4 = {version="1.20", optional=true}
-brotli = {version="3.3.0", optional=true}
 snap = "1"
-tempfile = {version="3", optional=true}
+atomicwrites = {version="0.2.2", optional=true}
+tempfile = "3.0"
 log = "0.4"
-serde = {version="1", features=["derive"]}
+serde = {version="1.0", features=["derive"]}
-serde_json = "1"
+serde_json = "1.0"
-num_cpus = "1"
+num_cpus = "1.2"
 fs2={version="0.4", optional=true}
-levenshtein_automata = "0.2"
+levenshtein_automata = "0.1"
+notify = {version="4", optional=true}
 uuid = { version = "0.8", features = ["v4", "serde"] }
-crossbeam = "0.8"
+crossbeam = "0.7"
 futures = {version = "0.3",  features=["thread-pool"] }
-tantivy-query-grammar = { version="0.14.0-dev", path="./query-grammar" }
+owning_ref = "0.4"
-stable_deref_trait = "1"
+stable_deref_trait = "1.0.0"
-rust-stemmers = "1"
+rust-stemmers = "1.2"
-downcast-rs = "1"
+downcast-rs = { version="1.0" }
+tantivy-query-grammar = { version="0.12", path="./query-grammar" }
 bitpacking = {version="0.8", default-features = false, features=["bitpacker4x"]}
-census = "0.4"
+census =  {path="../census"}
-fnv = "1"
+fnv = "1.0.6"
-thiserror = "1.0"
+owned-read = "0.4"
-htmlescape = "0.3"
+failure = "0.1"
-fail = "0.4"
+htmlescape = "0.3.1"
+fail = "0.3"
 murmurhash32 = "0.2"
 chrono = "0.4"
-smallvec = "1"
+smallvec = "1.0"
 rayon = "1"
-env_logger = "0.8"
-lru = "0.6"
 
 [target.'cfg(windows)'.dependencies]
 winapi = "0.3"
 
 [dev-dependencies]
-rand = "0.8"
+rand = "0.7"
 maplit = "1"
 matches = "0.1.8"
-proptest = "0.10"
-criterion = "0.3"
 
 [dev-dependencies.fail]
-version = "0.4"
+version = "0.3"
 features = ["failpoints"]
 
 [profile.release]
@@ -75,8 +74,7 @@ overflow-checks = true
 
 [features]
 default = ["mmap"]
-mmap = ["fs2", "tempfile", "memmap"]
+mmap = ["atomicwrites", "fs2", "memmap", "notify"]
-brotli-compression = ["brotli"]
 lz4-compression = ["lz4"]
 failpoints = ["fail/failpoints"]
 unstable = [] # useful for benches.
@@ -99,7 +97,3 @@ travis-ci = { repository = "tantivy-search/tantivy" }
 name = "failpoints"
 path = "tests/failpoints/mod.rs"
 required-features = ["fail/failpoints"]
-
-[[bench]]
-name = "analyzer"
-harness = false

README.md

@@ -5,6 +5,7 @@
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 [![Build status](https://ci.appveyor.com/api/projects/status/r7nb13kj23u8m9pj/branch/master?svg=true)](https://ci.appveyor.com/project/fulmicoton/tantivy/branch/master)
 [![Crates.io](https://img.shields.io/crates/v/tantivy.svg)](https://crates.io/crates/tantivy)
+[![Say Thanks!](https://img.shields.io/badge/Say%20Thanks-!-1EAEDB.svg)](https://saythanks.io/to/fulmicoton)
 
 ![Tantivy](https://tantivy-search.github.io/logo/tantivy-logo.png)
 
@@ -30,11 +31,12 @@ Tantivy is, in fact, strongly inspired by Lucene's design.
 
 # Benchmark
 
+Tantivy is typically faster than Lucene, but the results depend on 
+the nature of the queries in your workload.
+
 The following [benchmark](https://tantivy-search.github.io/bench/) break downs 
 performance for different type of queries / collection.
 
-Your mileage WILL vary depending on the nature of queries and their load.
-
 # Features
 
 - Full-text search
@@ -84,7 +86,7 @@ There are many ways to support this project.
 - Help with documentation by asking questions or submitting PRs
 - Contribute code (you can join [our Gitter](https://gitter.im/tantivy-search/tantivy))
 - Talk about Tantivy around you
-- [![Become a patron](https://c5.patreon.com/external/logo/become_a_patron_button.png)](https://www.patreon.com/fulmicoton)
+- Drop a word on on [![Say Thanks!](https://img.shields.io/badge/Say%20Thanks-!-1EAEDB.svg)](https://saythanks.io/to/fulmicoton) or even [![Become a patron](https://c5.patreon.com/external/logo/become_a_patron_button.png)](https://www.patreon.com/fulmicoton)
 
 # Contributing code
 

TODO.md

@@ -0,0 +1,9 @@
+- segment writer serializes if already flush
+- flush if exceed max doc. 
+- unit tests
+- reader from `IndexWriter`
+- configurable limit to flush 
+- bundle directory
+- add index worker when exceeds some doc limit
+- flush before prepare commit.
+- segment_writer should not receive a segment 

appveyor.yml

@@ -18,5 +18,5 @@ install:
 build: false
 
 test_script:
-  - REM SET RUST_LOG=tantivy,test & cargo test --all --verbose --no-default-features --features mmap
+  - REM SET RUST_LOG=tantivy,test & cargo test --verbose --no-default-features --features mmap
   - REM SET RUST_BACKTRACE=1 & cargo build --examples

benches/analyzer.rs

@@ -1,22 +0,0 @@
-use criterion::{criterion_group, criterion_main, Criterion};
-use tantivy::tokenizer::TokenizerManager;
-
-const ALICE_TXT: &'static str = include_str!("alice.txt");
-
-pub fn criterion_benchmark(c: &mut Criterion) {
-    let tokenizer_manager = TokenizerManager::default();
-    let tokenizer = tokenizer_manager.get("default").unwrap();
-    c.bench_function("default-tokenize-alice", |b| {
-        b.iter(|| {
-            let mut word_count = 0;
-            let mut token_stream = tokenizer.token_stream(ALICE_TXT);
-            while token_stream.advance() {
-                word_count += 1;
-            }
-            assert_eq!(word_count, 30_731);
-        })
-    });
-}
-
-criterion_group!(benches, criterion_benchmark);
-criterion_main!(benches);

examples/basic_search.rs

@@ -112,6 +112,18 @@ fn main() -> tantivy::Result<()> {
             limbs and branches that arch over the pool"
     ));
 
+    index_writer.add_document(doc!(
+    title => "Of Mice and Men",
+    body => "A few miles south of Soledad, the Salinas River drops in close to the hillside \
+            bank and runs deep and green. The water is warm too, for it has slipped twinkling \
+            over the yellow sands in the sunlight before reaching the narrow pool. On one \
+            side of the river the golden foothill slopes curve up to the strong and rocky \
+            Gabilan Mountains, but on the valley side the water is lined with trees—willows \
+            fresh and green with every spring, carrying in their lower leaf junctures the \
+            debris of the winter’s flooding; and sycamores with mottled, white, recumbent \
+            limbs and branches that arch over the pool"
+    ));
+
     // Multivalued field just need to be repeated.
     index_writer.add_document(doc!(
     title => "Frankenstein",

examples/custom_collector.rs

@@ -14,7 +14,7 @@ use tantivy::fastfield::FastFieldReader;
 use tantivy::query::QueryParser;
 use tantivy::schema::Field;
 use tantivy::schema::{Schema, FAST, INDEXED, TEXT};
-use tantivy::{doc, Index, Score, SegmentReader, TantivyError};
+use tantivy::{doc, Index, SegmentReader, TantivyError};
 
 #[derive(Default)]
 struct Stats {
@@ -114,7 +114,7 @@ struct StatsSegmentCollector {
 impl SegmentCollector for StatsSegmentCollector {
     type Fruit = Option<Stats>;
 
-    fn collect(&mut self, doc: u32, _score: Score) {
+    fn collect(&mut self, doc: u32, _score: f32) {
         let value = self.fast_field_reader.get(doc) as f64;
         self.stats.count += 1;
         self.stats.sum += value;

examples/faceted_search_with_tweaked_score.rs

@@ -1,98 +0,0 @@
-use std::collections::HashSet;
-use tantivy::collector::TopDocs;
-use tantivy::doc;
-use tantivy::query::BooleanQuery;
-use tantivy::schema::*;
-use tantivy::{DocId, Index, Score, SegmentReader};
-
-fn main() -> tantivy::Result<()> {
-    let mut schema_builder = Schema::builder();
-
-    let title = schema_builder.add_text_field("title", STORED);
-    let ingredient = schema_builder.add_facet_field("ingredient");
-
-    let schema = schema_builder.build();
-    let index = Index::create_in_ram(schema.clone());
-
-    let mut index_writer = index.writer(30_000_000)?;
-
-    index_writer.add_document(doc!(
-        title => "Fried egg",
-        ingredient => Facet::from("/ingredient/egg"),
-        ingredient => Facet::from("/ingredient/oil"),
-    ));
-    index_writer.add_document(doc!(
-        title => "Scrambled egg",
-        ingredient => Facet::from("/ingredient/egg"),
-        ingredient => Facet::from("/ingredient/butter"),
-        ingredient => Facet::from("/ingredient/milk"),
-        ingredient => Facet::from("/ingredient/salt"),
-    ));
-    index_writer.add_document(doc!(
-        title => "Egg rolls",
-        ingredient => Facet::from("/ingredient/egg"),
-        ingredient => Facet::from("/ingredient/garlic"),
-        ingredient => Facet::from("/ingredient/salt"),
-        ingredient => Facet::from("/ingredient/oil"),
-        ingredient => Facet::from("/ingredient/tortilla-wrap"),
-        ingredient => Facet::from("/ingredient/mushroom"),
-    ));
-    index_writer.commit()?;
-
-    let reader = index.reader()?;
-    let searcher = reader.searcher();
-    {
-        let facets = vec![
-            Facet::from("/ingredient/egg"),
-            Facet::from("/ingredient/oil"),
-            Facet::from("/ingredient/garlic"),
-            Facet::from("/ingredient/mushroom"),
-        ];
-        let query = BooleanQuery::new_multiterms_query(
-            facets
-                .iter()
-                .map(|key| Term::from_facet(ingredient, &key))
-                .collect(),
-        );
-        let top_docs_by_custom_score =
-            TopDocs::with_limit(2).tweak_score(move |segment_reader: &SegmentReader| {
-                let ingredient_reader = segment_reader.facet_reader(ingredient).unwrap();
-                let facet_dict = ingredient_reader.facet_dict();
-
-                let query_ords: HashSet<u64> = facets
-                    .iter()
-                    .filter_map(|key| facet_dict.term_ord(key.encoded_str()).unwrap())
-                    .collect();
-
-                let mut facet_ords_buffer: Vec<u64> = Vec::with_capacity(20);
-
-                move |doc: DocId, original_score: Score| {
-                    ingredient_reader.facet_ords(doc, &mut facet_ords_buffer);
-                    let missing_ingredients = facet_ords_buffer
-                        .iter()
-                        .filter(|ord| !query_ords.contains(ord))
-                        .count();
-                    let tweak = 1.0 / 4_f32.powi(missing_ingredients as i32);
-
-                    original_score * tweak
-                }
-            });
-        let top_docs = searcher.search(&query, &top_docs_by_custom_score)?;
-
-        let titles: Vec<String> = top_docs
-            .iter()
-            .map(|(_, doc_id)| {
-                searcher
-                    .doc(*doc_id)
-                    .unwrap()
-                    .get_first(title)
-                    .unwrap()
-                    .text()
-                    .unwrap()
-                    .to_owned()
-            })
-            .collect();
-        assert_eq!(titles, vec!["Fried egg", "Egg rolls"]);
-    }
-    Ok(())
-}

examples/iterating_docs_and_positions.rs

@@ -10,7 +10,7 @@
 // ---
 // Importing tantivy...
 use tantivy::schema::*;
-use tantivy::{doc, DocSet, Index, Postings, TERMINATED};
+use tantivy::{doc, DocId, DocSet, Index, Postings};
 
 fn main() -> tantivy::Result<()> {
     // We first create a schema for the sake of the
@@ -45,7 +45,7 @@ fn main() -> tantivy::Result<()> {
         // Inverted index stands for the combination of
         // - the term dictionary
         // - the inverted lists associated to each terms and their positions
-        let inverted_index = segment_reader.inverted_index(title)?;
+        let inverted_index = segment_reader.inverted_index(title);
 
         // A `Term` is a text token associated with a field.
         // Let's go through all docs containing the term `title:the` and access their position
@@ -58,15 +58,16 @@ fn main() -> tantivy::Result<()> {
         // If you don't need all this information, you may get better performance by decompressing less
         // information.
         if let Some(mut segment_postings) =
-            inverted_index.read_postings(&term_the, IndexRecordOption::WithFreqsAndPositions)?
+            inverted_index.read_postings(&term_the, IndexRecordOption::WithFreqsAndPositions)
         {
             // this buffer will be used to request for positions
             let mut positions: Vec<u32> = Vec::with_capacity(100);
-            let mut doc_id = segment_postings.doc();
+            while segment_postings.advance() {
-            while doc_id != TERMINATED {
+                // the number of time the term appears in the document.
+                let doc_id: DocId = segment_postings.doc(); //< do not try to access this before calling advance once.
+
                 // This MAY contains deleted documents as well.
                 if segment_reader.is_deleted(doc_id) {
-                    doc_id = segment_postings.advance();
                     continue;
                 }
 
@@ -85,7 +86,6 @@ fn main() -> tantivy::Result<()> {
                 // Doc 2: TermFreq 1: [0]
                 // ```
                 println!("Doc {}: TermFreq {}: {:?}", doc_id, term_freq, positions);
-                doc_id = segment_postings.advance();
             }
         }
     }
@@ -106,7 +106,7 @@ fn main() -> tantivy::Result<()> {
         // Inverted index stands for the combination of
         // - the term dictionary
         // - the inverted lists associated to each terms and their positions
-        let inverted_index = segment_reader.inverted_index(title)?;
+        let inverted_index = segment_reader.inverted_index(title);
 
         // This segment posting object is like a cursor over the documents matching the term.
         // The `IndexRecordOption` arguments tells tantivy we will be interested in both term frequencies
@@ -115,18 +115,13 @@ fn main() -> tantivy::Result<()> {
         // If you don't need all this information, you may get better performance by decompressing less
         // information.
         if let Some(mut block_segment_postings) =
-            inverted_index.read_block_postings(&term_the, IndexRecordOption::Basic)?
+            inverted_index.read_block_postings(&term_the, IndexRecordOption::Basic)
         {
-            loop {
+            while block_segment_postings.advance() {
-                let docs = block_segment_postings.docs();
-                if docs.is_empty() {
-                    break;
-                }
                 // Once again these docs MAY contains deleted documents as well.
                 let docs = block_segment_postings.docs();
                 // Prints `Docs [0, 2].`
                 println!("Docs {:?}", docs);
-                block_segment_postings.advance();
             }
         }
     }

query-grammar/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy-query-grammar"
-version = "0.14.0-dev"
+version = "0.12.0"
 authors = ["Paul Masurel <paul.masurel@gmail.com>"]
 license = "MIT"
 categories = ["database-implementations", "data-structures"]

query-grammar/src/occur.rs

@@ -31,12 +31,22 @@ impl Occur {
 
     /// Compose two occur values.
     pub fn compose(left: Occur, right: Occur) -> Occur {
-        match (left, right) {
+        match left {
-            (Occur::Should, _) => right,
+            Occur::Should => right,
-            (Occur::Must, Occur::MustNot) => Occur::MustNot,
+            Occur::Must => {
-            (Occur::Must, _) => Occur::Must,
+                if right == Occur::MustNot {
-            (Occur::MustNot, Occur::MustNot) => Occur::Must,
+                    Occur::MustNot
-            (Occur::MustNot, _) => Occur::MustNot,
+                } else {
+                    Occur::Must
+                }
+            }
+            Occur::MustNot => {
+                if right == Occur::MustNot {
+                    Occur::Must
+                } else {
+                    Occur::MustNot
+                }
+            }
         }
     }
 }
@@ -46,27 +56,3 @@ impl fmt::Display for Occur {
         f.write_char(self.to_char())
     }
 }
-
-#[cfg(test)]
-mod test {
-    use crate::Occur;
-
-    #[test]
-    fn test_occur_compose() {
-        assert_eq!(Occur::compose(Occur::Should, Occur::Should), Occur::Should);
-        assert_eq!(Occur::compose(Occur::Should, Occur::Must), Occur::Must);
-        assert_eq!(
-            Occur::compose(Occur::Should, Occur::MustNot),
-            Occur::MustNot
-        );
-        assert_eq!(Occur::compose(Occur::Must, Occur::Should), Occur::Must);
-        assert_eq!(Occur::compose(Occur::Must, Occur::Must), Occur::Must);
-        assert_eq!(Occur::compose(Occur::Must, Occur::MustNot), Occur::MustNot);
-        assert_eq!(
-            Occur::compose(Occur::MustNot, Occur::Should),
-            Occur::MustNot
-        );
-        assert_eq!(Occur::compose(Occur::MustNot, Occur::Must), Occur::MustNot);
-        assert_eq!(Occur::compose(Occur::MustNot, Occur::MustNot), Occur::Must);
-    }
-}

query-grammar/src/query_grammar.rs

@@ -9,10 +9,8 @@ use combine::{
 
 fn field<'a>() -> impl Parser<&'a str, Output = String> {
     (
-        (letter().or(char('_'))),
+        letter(),
-        many(satisfy(|c: char| {
+        many(satisfy(|c: char| c.is_alphanumeric() || c == '_')),
-            c.is_alphanumeric() || c == '_' || c == '-'
-        })),
     )
         .skip(char(':'))
         .map(|(s1, s2): (char, String)| format!("{}{}", s1, s2))
@@ -156,11 +154,17 @@ fn negate(expr: UserInputAST) -> UserInputAST {
     expr.unary(Occur::MustNot)
 }
 
+fn must(expr: UserInputAST) -> UserInputAST {
+    expr.unary(Occur::Must)
+}
+
 fn leaf<'a>() -> impl Parser<&'a str, Output = UserInputAST> {
     parser(|input| {
-        char('(')
+        char('-')
-            .with(ast())
+            .with(leaf())
-            .skip(char(')'))
+            .map(negate)
+            .or(char('+').with(leaf()).map(must))
+            .or(char('(').with(ast()).skip(char(')')))
             .or(char('*').map(|_| UserInputAST::from(UserInputLeaf::All)))
             .or(attempt(
                 string("NOT").skip(spaces1()).with(leaf()).map(negate),
@@ -172,17 +176,7 @@ fn leaf<'a>() -> impl Parser<&'a str, Output = UserInputAST> {
     })
 }
 
-fn occur_symbol<'a>() -> impl Parser<&'a str, Output = Occur> {
+fn positive_float_number<'a>() -> impl Parser<&'a str, Output = f32> {
-    char('-')
-        .map(|_| Occur::MustNot)
-        .or(char('+').map(|_| Occur::Must))
-}
-
-fn occur_leaf<'a>() -> impl Parser<&'a str, Output = (Option<Occur>, UserInputAST)> {
-    (optional(occur_symbol()), boosted_leaf())
-}
-
-fn positive_float_number<'a>() -> impl Parser<&'a str, Output = f64> {
     (many1(digit()), optional((char('.'), many1(digit())))).map(
         |(int_part, decimal_part_opt): (String, Option<(char, String)>)| {
             let mut float_str = int_part;
@@ -190,18 +184,18 @@ fn positive_float_number<'a>() -> impl Parser<&'a str, Output = f64> {
                 float_str.push(chr);
                 float_str.push_str(&decimal_str);
             }
-            float_str.parse::<f64>().unwrap()
+            float_str.parse::<f32>().unwrap()
         },
     )
 }
 
-fn boost<'a>() -> impl Parser<&'a str, Output = f64> {
+fn boost<'a>() -> impl Parser<&'a str, Output = f32> {
     (char('^'), positive_float_number()).map(|(_, boost)| boost)
 }
 
 fn boosted_leaf<'a>() -> impl Parser<&'a str, Output = UserInputAST> {
     (leaf(), optional(boost())).map(|(leaf, boost_opt)| match boost_opt {
-        Some(boost) if (boost - 1.0).abs() > std::f64::EPSILON => {
+        Some(boost) if (boost - 1.0).abs() > std::f32::EPSILON => {
             UserInputAST::Boost(Box::new(leaf), boost)
         }
         _ => leaf,
@@ -245,29 +239,21 @@ fn aggregate_binary_expressions(
     }
 }
 
-fn operand_leaf<'a>() -> impl Parser<&'a str, Output = (BinaryOperand, UserInputAST)> {
+pub fn ast<'a>() -> impl Parser<&'a str, Output = UserInputAST> {
-    (
+    let operand_leaf = (
         binary_operand().skip(spaces()),
         boosted_leaf().skip(spaces()),
-    )
+    );
-}
+    let boolean_expr = (boosted_leaf().skip(spaces().silent()), many1(operand_leaf))
-
-pub fn ast<'a>() -> impl Parser<&'a str, Output = UserInputAST> {
-    let boolean_expr = (boosted_leaf().skip(spaces()), many1(operand_leaf()))
         .map(|(left, right)| aggregate_binary_expressions(left, right));
-    let whitespace_separated_leaves = many1(occur_leaf().skip(spaces().silent())).map(
+    let whitespace_separated_leaves =
-        |subqueries: Vec<(Option<Occur>, UserInputAST)>| {
+        many1(boosted_leaf().skip(spaces().silent())).map(|subqueries: Vec<UserInputAST>| {
             if subqueries.len() == 1 {
-                let (occur_opt, ast) = subqueries.into_iter().next().unwrap();
+                subqueries.into_iter().next().unwrap()
-                match occur_opt.unwrap_or(Occur::Should) {
-                    Occur::Must | Occur::Should => ast,
-                    Occur::MustNot => UserInputAST::Clause(vec![(Some(Occur::MustNot), ast)]),
-                }
             } else {
                 UserInputAST::Clause(subqueries.into_iter().collect())
             }
-        },
+        });
-    );
     let expr = attempt(boolean_expr).or(whitespace_separated_leaves);
     spaces().with(expr).skip(spaces())
 }
@@ -281,16 +267,14 @@ pub fn parse_to_ast<'a>() -> impl Parser<&'a str, Output = UserInputAST> {
 #[cfg(test)]
 mod test {
 
-    type TestParseResult = Result<(), StringStreamError>;
-
     use super::*;
     use combine::parser::Parser;
 
-    pub fn nearly_equals(a: f64, b: f64) -> bool {
+    pub fn nearly_equals(a: f32, b: f32) -> bool {
         (a - b).abs() < 0.0005 * (a + b).abs()
     }
 
-    fn assert_nearly_equals(expected: f64, val: f64) {
+    fn assert_nearly_equals(expected: f32, val: f32) {
         assert!(
             nearly_equals(val, expected),
             "Got {}, expected {}.",
@@ -299,16 +283,9 @@ mod test {
         );
     }
 
-    #[test]
-    fn test_occur_symbol() -> TestParseResult {
-        assert_eq!(super::occur_symbol().parse("-")?, (Occur::MustNot, ""));
-        assert_eq!(super::occur_symbol().parse("+")?, (Occur::Must, ""));
-        Ok(())
-    }
-
     #[test]
     fn test_positive_float_number() {
-        fn valid_parse(float_str: &str, expected_val: f64, expected_remaining: &str) {
+        fn valid_parse(float_str: &str, expected_val: f32, expected_remaining: &str) {
             let (val, remaining) = positive_float_number().parse(float_str).unwrap();
             assert_eq!(remaining, expected_remaining);
             assert_nearly_equals(val, expected_val);
@@ -316,9 +293,9 @@ mod test {
         fn error_parse(float_str: &str) {
             assert!(positive_float_number().parse(float_str).is_err());
         }
-        valid_parse("1.0", 1.0, "");
+        valid_parse("1.0", 1.0f32, "");
-        valid_parse("1", 1.0, "");
+        valid_parse("1", 1.0f32, "");
-        valid_parse("0.234234 aaa", 0.234234f64, " aaa");
+        valid_parse("0.234234 aaa", 0.234234f32, " aaa");
         error_parse(".3332");
         error_parse("1.");
         error_parse("-1.");
@@ -353,7 +330,7 @@ mod test {
             "Err(UnexpectedParse)"
         );
         test_parse_query_to_ast_helper("NOTa", "\"NOTa\"");
-        test_parse_query_to_ast_helper("NOT a", "(-\"a\")");
+        test_parse_query_to_ast_helper("NOT a", "-(\"a\")");
     }
 
     #[test]
@@ -361,16 +338,16 @@ mod test {
         assert!(parse_to_ast().parse("a^2^3").is_err());
         assert!(parse_to_ast().parse("a^2^").is_err());
         test_parse_query_to_ast_helper("a^3", "(\"a\")^3");
-        test_parse_query_to_ast_helper("a^3 b^2", "(*(\"a\")^3 *(\"b\")^2)");
+        test_parse_query_to_ast_helper("a^3 b^2", "((\"a\")^3 (\"b\")^2)");
         test_parse_query_to_ast_helper("a^1", "\"a\"");
     }
 
     #[test]
     fn test_parse_query_to_ast_binary_op() {
-        test_parse_query_to_ast_helper("a AND b", "(+\"a\" +\"b\")");
+        test_parse_query_to_ast_helper("a AND b", "(+(\"a\") +(\"b\"))");
-        test_parse_query_to_ast_helper("a OR b", "(?\"a\" ?\"b\")");
+        test_parse_query_to_ast_helper("a OR b", "(?(\"a\") ?(\"b\"))");
-        test_parse_query_to_ast_helper("a OR b AND c", "(?\"a\" ?(+\"b\" +\"c\"))");
+        test_parse_query_to_ast_helper("a OR b AND c", "(?(\"a\") ?((+(\"b\") +(\"c\"))))");
-        test_parse_query_to_ast_helper("a AND b         AND c", "(+\"a\" +\"b\" +\"c\")");
+        test_parse_query_to_ast_helper("a AND b         AND c", "(+(\"a\") +(\"b\") +(\"c\"))");
         assert_eq!(
             format!("{:?}", parse_to_ast().parse("a OR b aaa")),
             "Err(UnexpectedParse)"
@@ -408,32 +385,6 @@ mod test {
         test_parse_query_to_ast_helper("weight: <= 70.5", "weight:{\"*\" TO \"70.5\"]");
     }
 
-    #[test]
-    fn test_occur_leaf() {
-        let ((occur, ast), _) = super::occur_leaf().parse("+abc").unwrap();
-        assert_eq!(occur, Some(Occur::Must));
-        assert_eq!(format!("{:?}", ast), "\"abc\"");
-    }
-
-    #[test]
-    fn test_field_name() -> TestParseResult {
-        assert_eq!(
-            super::field().parse("my-field-name:a")?,
-            ("my-field-name".to_string(), "a")
-        );
-        assert_eq!(
-            super::field().parse("my_field_name:a")?,
-            ("my_field_name".to_string(), "a")
-        );
-        assert!(super::field().parse(":a").is_err());
-        assert!(super::field().parse("-my_field:a").is_err());
-        assert_eq!(
-            super::field().parse("_my_field:a")?,
-            ("_my_field".to_string(), "a")
-        );
-        Ok(())
-    }
-
     #[test]
     fn test_range_parser() {
         // testing the range() parser separately
@@ -462,67 +413,32 @@ mod test {
     fn test_parse_query_to_triming_spaces() {
         test_parse_query_to_ast_helper("   abc", "\"abc\"");
         test_parse_query_to_ast_helper("abc ", "\"abc\"");
-        test_parse_query_to_ast_helper("(  a OR abc)", "(?\"a\" ?\"abc\")");
+        test_parse_query_to_ast_helper("(  a OR abc)", "(?(\"a\") ?(\"abc\"))");
-        test_parse_query_to_ast_helper("(a  OR abc)", "(?\"a\" ?\"abc\")");
+        test_parse_query_to_ast_helper("(a  OR abc)", "(?(\"a\") ?(\"abc\"))");
-        test_parse_query_to_ast_helper("(a OR  abc)", "(?\"a\" ?\"abc\")");
+        test_parse_query_to_ast_helper("(a OR  abc)", "(?(\"a\") ?(\"abc\"))");
-        test_parse_query_to_ast_helper("a OR abc ", "(?\"a\" ?\"abc\")");
+        test_parse_query_to_ast_helper("a OR abc ", "(?(\"a\") ?(\"abc\"))");
-        test_parse_query_to_ast_helper("(a OR abc )", "(?\"a\" ?\"abc\")");
+        test_parse_query_to_ast_helper("(a OR abc )", "(?(\"a\") ?(\"abc\"))");
-        test_parse_query_to_ast_helper("(a OR  abc) ", "(?\"a\" ?\"abc\")");
+        test_parse_query_to_ast_helper("(a OR  abc) ", "(?(\"a\") ?(\"abc\"))");
     }
 
     #[test]
-    fn test_parse_query_single_term() {
+    fn test_parse_query_to_ast() {
         test_parse_query_to_ast_helper("abc", "\"abc\"");
-    }
+        test_parse_query_to_ast_helper("a b", "(\"a\" \"b\")");
-
+        test_parse_query_to_ast_helper("+(a b)", "+((\"a\" \"b\"))");
-    #[test]
+        test_parse_query_to_ast_helper("+d", "+(\"d\")");
-    fn test_parse_query_default_clause() {
+        test_parse_query_to_ast_helper("+(a b) +d", "(+((\"a\" \"b\")) +(\"d\"))");
-        test_parse_query_to_ast_helper("a b", "(*\"a\" *\"b\")");
+        test_parse_query_to_ast_helper("(+a +b) d", "((+(\"a\") +(\"b\")) \"d\")");
-    }
+        test_parse_query_to_ast_helper("(+a)", "+(\"a\")");
-
+        test_parse_query_to_ast_helper("(+a +b)", "(+(\"a\") +(\"b\"))");
-    #[test]
-    fn test_parse_query_must_default_clause() {
-        test_parse_query_to_ast_helper("+(a b)", "(*\"a\" *\"b\")");
-    }
-
-    #[test]
-    fn test_parse_query_must_single_term() {
-        test_parse_query_to_ast_helper("+d", "\"d\"");
-    }
-
-    #[test]
-    fn test_single_term_with_field() {
         test_parse_query_to_ast_helper("abc:toto", "abc:\"toto\"");
-    }
-
-    #[test]
-    fn test_single_term_with_float() {
         test_parse_query_to_ast_helper("abc:1.1", "abc:\"1.1\"");
-    }
+        test_parse_query_to_ast_helper("+abc:toto", "+(abc:\"toto\")");
-
+        test_parse_query_to_ast_helper("(+abc:toto -titi)", "(+(abc:\"toto\") -(\"titi\"))");
-    #[test]
+        test_parse_query_to_ast_helper("-abc:toto", "-(abc:\"toto\")");
-    fn test_must_clause() {
+        test_parse_query_to_ast_helper("abc:a b", "(abc:\"a\" \"b\")");
-        test_parse_query_to_ast_helper("(+a +b)", "(+\"a\" +\"b\")");
-    }
-
-    #[test]
-    fn test_parse_test_query_plus_a_b_plus_d() {
-        test_parse_query_to_ast_helper("+(a b) +d", "(+(*\"a\" *\"b\") +\"d\")");
-    }
-
-    #[test]
-    fn test_parse_test_query_other() {
-        test_parse_query_to_ast_helper("(+a +b) d", "(*(+\"a\" +\"b\") *\"d\")");
-        test_parse_query_to_ast_helper("+abc:toto", "abc:\"toto\"");
-        test_parse_query_to_ast_helper("(+abc:toto -titi)", "(+abc:\"toto\" -\"titi\")");
-        test_parse_query_to_ast_helper("-abc:toto", "(-abc:\"toto\")");
-        test_parse_query_to_ast_helper("abc:a b", "(*abc:\"a\" *\"b\")");
         test_parse_query_to_ast_helper("abc:\"a b\"", "abc:\"a b\"");
         test_parse_query_to_ast_helper("foo:[1 TO 5]", "foo:[\"1\" TO \"5\"]");
-    }
-
-    #[test]
-    fn test_parse_query_with_range() {
         test_parse_query_to_ast_helper("[1 TO 5]", "[\"1\" TO \"5\"]");
         test_parse_query_to_ast_helper("foo:{a TO z}", "foo:{\"a\" TO \"z\"}");
         test_parse_query_to_ast_helper("foo:[1 TO toto}", "foo:[\"1\" TO \"toto\"}");

query-grammar/src/user_input_ast.rs

@@ -85,14 +85,15 @@ impl UserInputBound {
 }
 
 pub enum UserInputAST {
-    Clause(Vec<(Option<Occur>, UserInputAST)>),
+    Clause(Vec<UserInputAST>),
+    Unary(Occur, Box<UserInputAST>),
     Leaf(Box<UserInputLeaf>),
-    Boost(Box<UserInputAST>, f64),
+    Boost(Box<UserInputAST>, f32),
 }
 
 impl UserInputAST {
     pub fn unary(self, occur: Occur) -> UserInputAST {
-        UserInputAST::Clause(vec![(Some(occur), self)])
+        UserInputAST::Unary(occur, Box::new(self))
     }
 
     fn compose(occur: Occur, asts: Vec<UserInputAST>) -> UserInputAST {
@@ -103,7 +104,7 @@ impl UserInputAST {
         } else {
             UserInputAST::Clause(
                 asts.into_iter()
-                    .map(|ast: UserInputAST| (Some(occur), ast))
+                    .map(|ast: UserInputAST| ast.unary(occur))
                     .collect::<Vec<_>>(),
             )
         }
@@ -134,36 +135,25 @@ impl From<UserInputLeaf> for UserInputAST {
     }
 }
 
-fn print_occur_ast(
-    occur_opt: Option<Occur>,
-    ast: &UserInputAST,
-    formatter: &mut fmt::Formatter,
-) -> fmt::Result {
-    if let Some(occur) = occur_opt {
-        write!(formatter, "{}{:?}", occur, ast)?;
-    } else {
-        write!(formatter, "*{:?}", ast)?;
-    }
-    Ok(())
-}
-
 impl fmt::Debug for UserInputAST {
-    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
         match *self {
             UserInputAST::Clause(ref subqueries) => {
                 if subqueries.is_empty() {
                     write!(formatter, "<emptyclause>")?;
                 } else {
                     write!(formatter, "(")?;
-                    print_occur_ast(subqueries[0].0, &subqueries[0].1, formatter)?;
+                    write!(formatter, "{:?}", &subqueries[0])?;
                     for subquery in &subqueries[1..] {
-                        write!(formatter, " ")?;
+                        write!(formatter, " {:?}", subquery)?;
-                        print_occur_ast(subquery.0, &subquery.1, formatter)?;
                     }
                     write!(formatter, ")")?;
                 }
                 Ok(())
             }
+            UserInputAST::Unary(ref occur, ref subquery) => {
+                write!(formatter, "{}({:?})", occur, subquery)
+            }
             UserInputAST::Leaf(ref subquery) => write!(formatter, "{:?}", subquery),
             UserInputAST::Boost(ref leaf, boost) => write!(formatter, "({:?})^{}", leaf, boost),
         }

src/collector/count_collector.rs

@@ -96,18 +96,18 @@ mod tests {
         }
         {
             let mut count_collector = SegmentCountCollector::default();
-            count_collector.collect(0u32, 1.0);
+            count_collector.collect(0u32, 1f32);
             assert_eq!(count_collector.harvest(), 1);
         }
         {
             let mut count_collector = SegmentCountCollector::default();
-            count_collector.collect(0u32, 1.0);
+            count_collector.collect(0u32, 1f32);
             assert_eq!(count_collector.harvest(), 1);
         }
         {
             let mut count_collector = SegmentCountCollector::default();
-            count_collector.collect(0u32, 1.0);
+            count_collector.collect(0u32, 1f32);
-            count_collector.collect(1u32, 1.0);
+            count_collector.collect(1u32, 1f32);
             assert_eq!(count_collector.harvest(), 2);
         }
     }

src/collector/custom_score_top_collector.rs

@@ -11,13 +11,13 @@ impl<TCustomScorer, TScore> CustomScoreTopCollector<TCustomScorer, TScore>
 where
     TScore: Clone + PartialOrd,
 {
-    pub(crate) fn new(
+    pub fn new(
         custom_scorer: TCustomScorer,
-        collector: TopCollector<TScore>,
+        limit: usize,
     ) -> CustomScoreTopCollector<TCustomScorer, TScore> {
         CustomScoreTopCollector {
             custom_scorer,
-            collector,
+            collector: TopCollector::with_limit(limit),
         }
     }
 }
@@ -28,7 +28,7 @@ where
 /// It is the segment local version of the [`CustomScorer`](./trait.CustomScorer.html).
 pub trait CustomSegmentScorer<TScore>: 'static {
     /// Computes the score of a specific `doc`.
-    fn score(&mut self, doc: DocId) -> TScore;
+    fn score(&self, doc: DocId) -> TScore;
 }
 
 /// `CustomScorer` makes it possible to define any kind of score.
@@ -46,7 +46,7 @@ pub trait CustomScorer<TScore>: Sync {
 
 impl<TCustomScorer, TScore> Collector for CustomScoreTopCollector<TCustomScorer, TScore>
 where
-    TCustomScorer: CustomScorer<TScore> + Send + Sync,
+    TCustomScorer: CustomScorer<TScore>,
     TScore: 'static + PartialOrd + Clone + Send + Sync,
 {
     type Fruit = Vec<(TScore, DocAddress)>;
@@ -58,10 +58,10 @@ where
         segment_local_id: u32,
         segment_reader: &SegmentReader,
     ) -> crate::Result<Self::Child> {
+        let segment_scorer = self.custom_scorer.segment_scorer(segment_reader)?;
         let segment_collector = self
             .collector
             .for_segment(segment_local_id, segment_reader)?;
-        let segment_scorer = self.custom_scorer.segment_scorer(segment_reader)?;
         Ok(CustomScoreTopSegmentCollector {
             segment_collector,
             segment_scorer,
@@ -117,9 +117,9 @@ where
 
 impl<F, TScore> CustomSegmentScorer<TScore> for F
 where
-    F: 'static + FnMut(DocId) -> TScore,
+    F: 'static + Sync + Send + Fn(DocId) -> TScore,
 {
-    fn score(&mut self, doc: DocId) -> TScore {
+    fn score(&self, doc: DocId) -> TScore {
         (self)(doc)
     }
 }

src/collector/docset_collector.rs

@@ -1,61 +0,0 @@
-use std::collections::HashSet;
-
-use crate::{DocAddress, DocId, Score};
-
-use super::{Collector, SegmentCollector};
-
-/// Collectors that returns the set of DocAddress that matches the query.
-///
-/// This collector is mostly useful for tests.
-pub struct DocSetCollector;
-
-impl Collector for DocSetCollector {
-    type Fruit = HashSet<DocAddress>;
-    type Child = DocSetChildCollector;
-
-    fn for_segment(
-        &self,
-        segment_local_id: crate::SegmentLocalId,
-        _segment: &crate::SegmentReader,
-    ) -> crate::Result<Self::Child> {
-        Ok(DocSetChildCollector {
-            segment_local_id,
-            docs: HashSet::new(),
-        })
-    }
-
-    fn requires_scoring(&self) -> bool {
-        false
-    }
-
-    fn merge_fruits(
-        &self,
-        segment_fruits: Vec<(u32, HashSet<DocId>)>,
-    ) -> crate::Result<Self::Fruit> {
-        let len: usize = segment_fruits.iter().map(|(_, docset)| docset.len()).sum();
-        let mut result = HashSet::with_capacity(len);
-        for (segment_local_id, docs) in segment_fruits {
-            for doc in docs {
-                result.insert(DocAddress(segment_local_id, doc));
-            }
-        }
-        Ok(result)
-    }
-}
-
-pub struct DocSetChildCollector {
-    segment_local_id: u32,
-    docs: HashSet<DocId>,
-}
-
-impl SegmentCollector for DocSetChildCollector {
-    type Fruit = (u32, HashSet<DocId>);
-
-    fn collect(&mut self, doc: crate::DocId, _score: Score) {
-        self.docs.insert(doc);
-    }
-
-    fn harvest(self) -> (u32, HashSet<DocId>) {
-        (self.segment_local_id, self.docs)
-    }
-}

src/collector/facet_collector.rs

@@ -1,5 +1,6 @@
 use crate::collector::Collector;
 use crate::collector::SegmentCollector;
+use crate::docset::SkipResult;
 use crate::fastfield::FacetReader;
 use crate::schema::Facet;
 use crate::schema::Field;
@@ -7,6 +8,7 @@ use crate::DocId;
 use crate::Score;
 use crate::SegmentLocalId;
 use crate::SegmentReader;
+use crate::TantivyError;
 use std::cmp::Ordering;
 use std::collections::btree_map;
 use std::collections::BTreeMap;
@@ -186,11 +188,6 @@ pub struct FacetSegmentCollector {
     collapse_facet_ords: Vec<u64>,
 }
 
-enum SkipResult {
-    Found,
-    NotFound,
-}
-
 fn skip<'a, I: Iterator<Item = &'a Facet>>(
     target: &[u8],
     collapse_it: &mut Peekable<I>,
@@ -200,14 +197,14 @@ fn skip<'a, I: Iterator<Item = &'a Facet>>(
             Some(facet_bytes) => match facet_bytes.encoded_str().as_bytes().cmp(target) {
                 Ordering::Less => {}
                 Ordering::Greater => {
-                    return SkipResult::NotFound;
+                    return SkipResult::OverStep;
                 }
                 Ordering::Equal => {
-                    return SkipResult::Found;
+                    return SkipResult::Reached;
                 }
             },
             None => {
-                return SkipResult::NotFound;
+                return SkipResult::End;
             }
         }
         collapse_it.next();
@@ -265,7 +262,10 @@ impl Collector for FacetCollector {
         _: SegmentLocalId,
         reader: &SegmentReader,
     ) -> crate::Result<FacetSegmentCollector> {
-        let facet_reader = reader.facet_reader(self.field)?;
+        let field_name = reader.schema().get_field_name(self.field);
+        let facet_reader = reader.facet_reader(self.field).ok_or_else(|| {
+            TantivyError::SchemaError(format!("Field {:?} is not a facet field.", field_name))
+        })?;
 
         let mut collapse_mapping = Vec::new();
         let mut counts = Vec::new();
@@ -274,14 +274,14 @@ impl Collector for FacetCollector {
         let mut collapse_facet_it = self.facets.iter().peekable();
         collapse_facet_ords.push(0);
         {
-            let mut facet_streamer = facet_reader.facet_dict().range().into_stream()?;
+            let mut facet_streamer = facet_reader.facet_dict().range().into_stream();
             if facet_streamer.advance() {
                 'outer: loop {
                     // at the begining of this loop, facet_streamer
                     // is positionned on a term that has not been processed yet.
                     let skip_result = skip(facet_streamer.key(), &mut collapse_facet_it);
                     match skip_result {
-                        SkipResult::Found => {
+                        SkipResult::Reached => {
                             // we reach a facet we decided to collapse.
                             let collapse_depth = facet_depth(facet_streamer.key());
                             let mut collapsed_id = 0;
@@ -301,7 +301,7 @@ impl Collector for FacetCollector {
                             }
                             break;
                         }
-                        SkipResult::NotFound => {
+                        SkipResult::End | SkipResult::OverStep => {
                             collapse_mapping.push(0);
                             if !facet_streamer.advance() {
                                 break;
@@ -368,12 +368,9 @@ impl SegmentCollector for FacetSegmentCollector {
             }
             let mut facet = vec![];
             let facet_ord = self.collapse_facet_ords[collapsed_facet_ord];
-            // TODO handle errors.
+            facet_dict.ord_to_term(facet_ord as u64, &mut facet);
-            if facet_dict.ord_to_term(facet_ord as u64, &mut facet).is_ok() {
+            // TODO
-                if let Ok(facet) = Facet::from_encoded(facet) {
+            facet_counts.insert(Facet::from_encoded(facet).unwrap(), count);
-                    facet_counts.insert(facet, count);
-                }
-            }
         }
         FacetCounts { facet_counts }
     }
@@ -471,7 +468,7 @@ mod tests {
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let num_facets: usize = 3 * 4 * 5;
         let facets: Vec<Facet> = (0..num_facets)
             .map(|mut n| {
@@ -530,7 +527,7 @@ mod tests {
         let facet_field = schema_builder.add_facet_field("facets");
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(
             facet_field => Facet::from_text(&"/subjects/A/a"),
             facet_field => Facet::from_text(&"/subjects/B/a"),
@@ -549,12 +546,12 @@ mod tests {
     }
 
     #[test]
-    fn test_doc_search_by_facet() -> crate::Result<()> {
+    fn test_doc_search_by_facet() {
         let mut schema_builder = Schema::builder();
         let facet_field = schema_builder.add_facet_field("facet");
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(
             facet_field => Facet::from_text(&"/A/A"),
         ));
@@ -567,8 +564,8 @@ mod tests {
         index_writer.add_document(doc!(
             facet_field => Facet::from_text(&"/D/C/A"),
         ));
-        index_writer.commit()?;
+        index_writer.commit().unwrap();
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         assert_eq!(searcher.num_docs(), 4);
 
@@ -585,17 +582,17 @@ mod tests {
         assert_eq!(count_facet("/A/C"), 1);
         assert_eq!(count_facet("/A/C/A"), 1);
         assert_eq!(count_facet("/C/A"), 0);
-
-        let query_parser = QueryParser::for_index(&index, vec![]);
         {
-            let query = query_parser.parse_query("facet:/A/B")?;
+            let query_parser = QueryParser::for_index(&index, vec![]);
-            assert_eq!(1, searcher.search(&query, &Count).unwrap());
+            {
+                let query = query_parser.parse_query("facet:/A/B").unwrap();
+                assert_eq!(1, searcher.search(&query, &Count).unwrap());
+            }
+            {
+                let query = query_parser.parse_query("facet:/A").unwrap();
+                assert_eq!(3, searcher.search(&query, &Count).unwrap());
+            }
         }
-        {
-            let query = query_parser.parse_query("facet:/A")?;
-            assert_eq!(3, searcher.search(&query, &Count)?);
-        }
-        Ok(())
     }
 
     #[test]
@@ -630,7 +627,7 @@ mod tests {
             .collect();
         docs[..].shuffle(&mut thread_rng());
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         for doc in docs {
             index_writer.add_document(doc);
         }
@@ -683,7 +680,7 @@ mod bench {
         // 40425 docs
         docs[..].shuffle(&mut thread_rng());
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         for doc in docs {
             index_writer.add_document(doc);
         }

src/collector/filter_collector_wrapper.rs

@@ -1,189 +0,0 @@
-// # Custom collector example
-//
-// This example shows how you can implement your own
-// collector. As an example, we will compute a collector
-// that computes the standard deviation of a given fast field.
-//
-// Of course, you can have a look at the tantivy's built-in collectors
-// such as the `CountCollector` for more examples.
-
-// ---
-// Importing tantivy...
-use std::marker::PhantomData;
-
-use crate::collector::{Collector, SegmentCollector};
-use crate::fastfield::{FastFieldReader, FastValue};
-use crate::schema::Field;
-use crate::{Score, SegmentReader, TantivyError};
-
-/// The `FilterCollector` collector filters docs using a u64 fast field value and a predicate.
-/// Only the documents for which the predicate returned "true" will be passed on to the next collector.
-///
-/// ```rust
-/// use tantivy::collector::{TopDocs, FilterCollector};
-/// use tantivy::query::QueryParser;
-/// use tantivy::schema::{Schema, TEXT, INDEXED, FAST};
-/// use tantivy::{doc, DocAddress, Index};
-///
-/// let mut schema_builder = Schema::builder();
-/// let title = schema_builder.add_text_field("title", TEXT);
-/// let price = schema_builder.add_u64_field("price", INDEXED | FAST);
-/// let schema = schema_builder.build();
-/// let index = Index::create_in_ram(schema);
-///
-/// let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
-/// index_writer.add_document(doc!(title => "The Name of the Wind", price => 30_200u64));
-/// index_writer.add_document(doc!(title => "The Diary of Muadib", price => 29_240u64));
-/// index_writer.add_document(doc!(title => "A Dairy Cow", price => 21_240u64));
-/// index_writer.add_document(doc!(title => "The Diary of a Young Girl", price => 20_120u64));
-/// assert!(index_writer.commit().is_ok());
-///
-/// let reader = index.reader().unwrap();
-/// let searcher = reader.searcher();
-///
-/// let query_parser = QueryParser::for_index(&index, vec![title]);
-/// let query = query_parser.parse_query("diary").unwrap();
-/// let no_filter_collector = FilterCollector::new(price, &|value: u64| value > 20_120u64, TopDocs::with_limit(2));
-/// let top_docs = searcher.search(&query, &no_filter_collector).unwrap();
-///
-/// assert_eq!(top_docs.len(), 1);
-/// assert_eq!(top_docs[0].1, DocAddress(0, 1));
-///
-/// let filter_all_collector: FilterCollector<_, _, u64> = FilterCollector::new(price, &|value| value < 5u64, TopDocs::with_limit(2));
-/// let filtered_top_docs = searcher.search(&query, &filter_all_collector).unwrap();
-///
-/// assert_eq!(filtered_top_docs.len(), 0);
-/// ```
-pub struct FilterCollector<TCollector, TPredicate, TPredicateValue: FastValue>
-where
-    TPredicate: 'static,
-{
-    field: Field,
-    collector: TCollector,
-    predicate: &'static TPredicate,
-    t_predicate_value: PhantomData<TPredicateValue>,
-}
-
-impl<TCollector, TPredicate, TPredicateValue: FastValue>
-    FilterCollector<TCollector, TPredicate, TPredicateValue>
-where
-    TCollector: Collector + Send + Sync,
-    TPredicate: Fn(TPredicateValue) -> bool + Send + Sync,
-{
-    /// Create a new FilterCollector.
-    pub fn new(
-        field: Field,
-        predicate: &'static TPredicate,
-        collector: TCollector,
-    ) -> FilterCollector<TCollector, TPredicate, TPredicateValue> {
-        FilterCollector {
-            field,
-            predicate,
-            collector,
-            t_predicate_value: PhantomData,
-        }
-    }
-}
-
-impl<TCollector, TPredicate, TPredicateValue: FastValue> Collector
-    for FilterCollector<TCollector, TPredicate, TPredicateValue>
-where
-    TCollector: Collector + Send + Sync,
-    TPredicate: 'static + Fn(TPredicateValue) -> bool + Send + Sync,
-    TPredicateValue: 'static + FastValue,
-{
-    // That's the type of our result.
-    // Our standard deviation will be a float.
-    type Fruit = TCollector::Fruit;
-
-    type Child = FilterSegmentCollector<TCollector::Child, TPredicate, TPredicateValue>;
-
-    fn for_segment(
-        &self,
-        segment_local_id: u32,
-        segment_reader: &SegmentReader,
-    ) -> crate::Result<FilterSegmentCollector<TCollector::Child, TPredicate, TPredicateValue>> {
-        let schema = segment_reader.schema();
-        let field_entry = schema.get_field_entry(self.field);
-        if !field_entry.is_fast() {
-            return Err(TantivyError::SchemaError(format!(
-                "Field {:?} is not a fast field.",
-                field_entry.name()
-            )));
-        }
-        let requested_type = TPredicateValue::to_type();
-        let field_schema_type = field_entry.field_type().value_type();
-        if requested_type != field_schema_type {
-            return Err(TantivyError::SchemaError(format!(
-                "Field {:?} is of type {:?}!={:?}",
-                field_entry.name(),
-                requested_type,
-                field_schema_type
-            )));
-        }
-
-        let fast_field_reader = segment_reader
-            .fast_fields()
-            .typed_fast_field_reader(self.field)
-            .ok_or_else(|| {
-                TantivyError::SchemaError(format!(
-                    "{:?} is not declared as a fast field in the schema.",
-                    self.field
-                ))
-            })?;
-
-        let segment_collector = self
-            .collector
-            .for_segment(segment_local_id, segment_reader)?;
-
-        Ok(FilterSegmentCollector {
-            fast_field_reader,
-            segment_collector,
-            predicate: self.predicate,
-            t_predicate_value: PhantomData,
-        })
-    }
-
-    fn requires_scoring(&self) -> bool {
-        self.collector.requires_scoring()
-    }
-
-    fn merge_fruits(
-        &self,
-        segment_fruits: Vec<<TCollector::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<TCollector::Fruit> {
-        self.collector.merge_fruits(segment_fruits)
-    }
-}
-
-pub struct FilterSegmentCollector<TSegmentCollector, TPredicate, TPredicateValue>
-where
-    TPredicate: 'static,
-    TPredicateValue: 'static + FastValue,
-{
-    fast_field_reader: FastFieldReader<TPredicateValue>,
-    segment_collector: TSegmentCollector,
-    predicate: &'static TPredicate,
-    t_predicate_value: PhantomData<TPredicateValue>,
-}
-
-impl<TSegmentCollector, TPredicate, TPredicateValue> SegmentCollector
-    for FilterSegmentCollector<TSegmentCollector, TPredicate, TPredicateValue>
-where
-    TSegmentCollector: SegmentCollector,
-    TPredicate: 'static + Fn(TPredicateValue) -> bool + Send + Sync,
-    TPredicateValue: 'static + FastValue,
-{
-    type Fruit = TSegmentCollector::Fruit;
-
-    fn collect(&mut self, doc: u32, score: Score) {
-        let value = self.fast_field_reader.get(doc);
-        if (self.predicate)(value) {
-            self.segment_collector.collect(doc, score)
-        }
-    }
-
-    fn harvest(self) -> <TSegmentCollector as SegmentCollector>::Fruit {
-        self.segment_collector.harvest()
-    }
-}

src/collector/int_facet_collector.rs

@@ -0,0 +1,127 @@
+use std::cmp::Eq;
+use std::collections::HashMap;
+use std::hash::Hash;
+
+use collector::Collector;
+use fastfield::FastFieldReader;
+use schema::Field;
+
+use DocId;
+use Result;
+use Score;
+use SegmentReader;
+use SegmentLocalId;
+
+
+/// Facet collector  for i64/u64 fast field
+pub struct IntFacetCollector<T>
+where
+    T: FastFieldReader,
+    T::ValueType: Eq + Hash,
+{
+    counters: HashMap<T::ValueType, u64>,
+    field: Field,
+    ff_reader: Option<T>,
+}
+
+
+impl<T> IntFacetCollector<T>
+where
+    T: FastFieldReader,
+    T::ValueType: Eq + Hash,
+{
+    /// Creates a new facet collector for aggregating a given field.
+    pub fn new(field: Field) -> IntFacetCollector<T> {
+        IntFacetCollector {
+            counters: HashMap::new(),
+            field: field,
+            ff_reader: None,
+        }
+    }
+}
+
+
+impl<T> Collector for IntFacetCollector<T>
+where
+    T: FastFieldReader,
+    T::ValueType: Eq + Hash,
+{
+    fn set_segment(&mut self, _: SegmentLocalId, reader: &SegmentReader) -> Result<()> {
+        self.ff_reader = Some(reader.get_fast_field_reader(self.field)?);
+        Ok(())
+    }
+
+    fn collect(&mut self, doc: DocId, _: Score) {
+        let val = self.ff_reader
+            .as_ref()
+            .expect(
+                "collect() was called before set_segment. \
+                This should never happen.",
+            )
+            .get(doc);
+        *(self.counters.entry(val).or_insert(0)) += 1;
+    }
+}
+
+
+
+#[cfg(test)]
+mod tests {
+
+    use collector::{chain, IntFacetCollector};
+    use query::QueryParser;
+    use fastfield::{I64FastFieldReader, U64FastFieldReader};
+    use schema::{self, FAST, STRING};
+    use Index;
+
+    #[test]
+    // create 10 documents, set num field value to 0 or 1 for even/odd ones
+    // make sure we have facet counters correctly filled
+    fn test_facet_collector_results() {
+
+        let mut schema_builder = schema::Schema::builder();
+        let num_field_i64 = schema_builder.add_i64_field("num_i64", FAST);
+        let num_field_u64 = schema_builder.add_u64_field("num_u64", FAST);
+        let num_field_f64 = schema_builder.add_f64_field("num_f64", FAST);
+        let text_field = schema_builder.add_text_field("text", STRING);
+        let schema = schema_builder.build();
+
+        let index = Index::create_in_ram(schema.clone());
+
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            {
+                for i in 0u64..10u64 {
+                    index_writer.add_document(doc!(
+                        num_field_i64 => ((i as i64) % 3i64) as i64,
+                        num_field_u64 => (i % 2u64) as u64,
+                        num_field_f64 => (i % 4u64) as f64,
+                        text_field => "text"
+                    ));
+                }
+            }
+            assert_eq!(index_writer.commit().unwrap(), 10u64);
+        }
+
+        let searcher = index.reader().searcher();
+        let mut ffvf_i64: IntFacetCollector<I64FastFieldReader> = IntFacetCollector::new(num_field_i64);
+        let mut ffvf_u64: IntFacetCollector<U64FastFieldReader> = IntFacetCollector::new(num_field_u64);
+        let mut ffvf_f64: IntFacetCollector<F64FastFieldReader> = IntFacetCollector::new(num_field_f64);
+
+        {
+            // perform the query
+            let mut facet_collectors = chain().push(&mut ffvf_i64).push(&mut ffvf_u64).push(&mut ffvf_f64);
+            let mut query_parser = QueryParser::for_index(index, vec![text_field]);
+            let query = query_parser.parse_query("text:text").unwrap();
+            query.search(&searcher, &mut facet_collectors).unwrap();
+        }
+
+        assert_eq!(ffvf_u64.counters[&0], 5);
+        assert_eq!(ffvf_u64.counters[&1], 5);
+        assert_eq!(ffvf_i64.counters[&0], 4);
+        assert_eq!(ffvf_i64.counters[&1], 3);
+        assert_eq!(ffvf_f64.counters[&0.0], 3);
+        assert_eq!(ffvf_f64.counters[&2.0], 2);
+
+    }
+}

src/collector/mod.rs

@@ -109,13 +109,6 @@ pub use self::tweak_score_top_collector::{ScoreSegmentTweaker, ScoreTweaker};
 
 mod facet_collector;
 pub use self::facet_collector::FacetCollector;
-use crate::query::Weight;
-
-mod docset_collector;
-pub use self::docset_collector::DocSetCollector;
-
-mod filter_collector_wrapper;
-pub use self::filter_collector_wrapper::FilterCollector;
 
 /// `Fruit` is the type for the result of our collection.
 /// e.g. `usize` for the `Count` collector.
@@ -139,13 +132,13 @@ impl<T> Fruit for T where T: Send + downcast_rs::Downcast {}
 /// The collection logic itself is in the `SegmentCollector`.
 ///
 /// Segments are not guaranteed to be visited in any specific order.
-pub trait Collector: Sync + Send {
+pub trait Collector: Sync {
     /// `Fruit` is the type for the result of our collection.
     /// e.g. `usize` for the `Count` collector.
     type Fruit: Fruit;
 
     /// Type of the `SegmentCollector` associated to this collector.
-    type Child: SegmentCollector;
+    type Child: SegmentCollector<Fruit = Self::Fruit>;
 
     /// `set_segment` is called before beginning to enumerate
     /// on this segment.
@@ -160,33 +153,7 @@ pub trait Collector: Sync + Send {
 
     /// Combines the fruit associated to the collection of each segments
     /// into one fruit.
-    fn merge_fruits(
+    fn merge_fruits(&self, segment_fruits: Vec<Self::Fruit>) -> crate::Result<Self::Fruit>;
-        &self,
-        segment_fruits: Vec<<Self::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<Self::Fruit>;
-
-    /// Created a segment collector and
-    fn collect_segment(
-        &self,
-        weight: &dyn Weight,
-        segment_ord: u32,
-        reader: &SegmentReader,
-    ) -> crate::Result<<Self::Child as SegmentCollector>::Fruit> {
-        let mut segment_collector = self.for_segment(segment_ord as u32, reader)?;
-
-        if let Some(delete_bitset) = reader.delete_bitset() {
-            weight.for_each(reader, &mut |doc, score| {
-                if delete_bitset.is_alive(doc) {
-                    segment_collector.collect(doc, score);
-                }
-            })?;
-        } else {
-            weight.for_each(reader, &mut |doc, score| {
-                segment_collector.collect(doc, score);
-            })?;
-        }
-        Ok(segment_collector.harvest())
-    }
 }
 
 /// The `SegmentCollector` is the trait in charge of defining the
@@ -233,11 +200,11 @@ where
 
     fn merge_fruits(
         &self,
-        segment_fruits: Vec<<Self::Child as SegmentCollector>::Fruit>,
+        children: Vec<(Left::Fruit, Right::Fruit)>,
     ) -> crate::Result<(Left::Fruit, Right::Fruit)> {
         let mut left_fruits = vec![];
         let mut right_fruits = vec![];
-        for (left_fruit, right_fruit) in segment_fruits {
+        for (left_fruit, right_fruit) in children {
             left_fruits.push(left_fruit);
             right_fruits.push(right_fruit);
         }
@@ -291,10 +258,7 @@ where
         self.0.requires_scoring() || self.1.requires_scoring() || self.2.requires_scoring()
     }
 
-    fn merge_fruits(
+    fn merge_fruits(&self, children: Vec<Self::Fruit>) -> crate::Result<Self::Fruit> {
-        &self,
-        children: Vec<<Self::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<Self::Fruit> {
         let mut one_fruits = vec![];
         let mut two_fruits = vec![];
         let mut three_fruits = vec![];
@@ -361,10 +325,7 @@ where
             || self.3.requires_scoring()
     }
 
-    fn merge_fruits(
+    fn merge_fruits(&self, children: Vec<Self::Fruit>) -> crate::Result<Self::Fruit> {
-        &self,
-        children: Vec<<Self::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<Self::Fruit> {
         let mut one_fruits = vec![];
         let mut two_fruits = vec![];
         let mut three_fruits = vec![];

src/collector/multi_collector.rs

@@ -34,13 +34,13 @@ impl<TCollector: Collector> Collector for CollectorWrapper<TCollector> {
 
     fn merge_fruits(
         &self,
-        children: Vec<<Self::Child as SegmentCollector>::Fruit>,
+        children: Vec<<Self as Collector>::Fruit>,
     ) -> crate::Result<Box<dyn Fruit>> {
-        let typed_fruit: Vec<<TCollector::Child as SegmentCollector>::Fruit> = children
+        let typed_fruit: Vec<TCollector::Fruit> = children
             .into_iter()
             .map(|untyped_fruit| {
                 untyped_fruit
-                    .downcast::<<TCollector::Child as SegmentCollector>::Fruit>()
+                    .downcast::<TCollector::Fruit>()
                     .map(|boxed_but_typed| *boxed_but_typed)
                     .map_err(|_| {
                         TantivyError::InvalidArgument("Failed to cast child fruit.".to_string())
@@ -55,7 +55,7 @@ impl<TCollector: Collector> Collector for CollectorWrapper<TCollector> {
 impl SegmentCollector for Box<dyn BoxableSegmentCollector> {
     type Fruit = Box<dyn Fruit>;
 
-    fn collect(&mut self, doc: u32, score: Score) {
+    fn collect(&mut self, doc: u32, score: f32) {
         self.as_mut().collect(doc, score);
     }
 
@@ -65,7 +65,7 @@ impl SegmentCollector for Box<dyn BoxableSegmentCollector> {
 }
 
 pub trait BoxableSegmentCollector {
-    fn collect(&mut self, doc: u32, score: Score);
+    fn collect(&mut self, doc: u32, score: f32);
     fn harvest_from_box(self: Box<Self>) -> Box<dyn Fruit>;
 }
 
@@ -74,7 +74,7 @@ pub struct SegmentCollectorWrapper<TSegmentCollector: SegmentCollector>(TSegment
 impl<TSegmentCollector: SegmentCollector> BoxableSegmentCollector
     for SegmentCollectorWrapper<TSegmentCollector>
 {
-    fn collect(&mut self, doc: u32, score: Score) {
+    fn collect(&mut self, doc: u32, score: f32) {
         self.0.collect(doc, score);
     }
 
@@ -259,7 +259,7 @@ mod tests {
 
         let index = Index::create_in_ram(schema);
         {
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.add_document(doc!(text=>"abc"));
             index_writer.add_document(doc!(text=>"abc abc abc"));
             index_writer.add_document(doc!(text=>"abc abc"));

src/collector/tests.rs

@@ -8,13 +8,6 @@ use crate::DocId;
 use crate::Score;
 use crate::SegmentLocalId;
 
-use crate::collector::{FilterCollector, TopDocs};
-use crate::query::QueryParser;
-use crate::schema::{Schema, FAST, TEXT};
-use crate::DateTime;
-use crate::{doc, Index};
-use std::str::FromStr;
-
 pub const TEST_COLLECTOR_WITH_SCORE: TestCollector = TestCollector {
     compute_score: true,
 };
@@ -23,54 +16,6 @@ pub const TEST_COLLECTOR_WITHOUT_SCORE: TestCollector = TestCollector {
     compute_score: true,
 };
 
-#[test]
-pub fn test_filter_collector() {
-    let mut schema_builder = Schema::builder();
-    let title = schema_builder.add_text_field("title", TEXT);
-    let price = schema_builder.add_u64_field("price", FAST);
-    let date = schema_builder.add_date_field("date", FAST);
-    let schema = schema_builder.build();
-    let index = Index::create_in_ram(schema);
-
-    let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
-    index_writer.add_document(doc!(title => "The Name of the Wind", price => 30_200u64, date => DateTime::from_str("1898-04-09T00:00:00+00:00").unwrap()));
-    index_writer.add_document(doc!(title => "The Diary of Muadib", price => 29_240u64, date => DateTime::from_str("2020-04-09T00:00:00+00:00").unwrap()));
-    index_writer.add_document(doc!(title => "The Diary of Anne Frank", price => 18_240u64, date => DateTime::from_str("2019-04-20T00:00:00+00:00").unwrap()));
-    index_writer.add_document(doc!(title => "A Dairy Cow", price => 21_240u64, date => DateTime::from_str("2019-04-09T00:00:00+00:00").unwrap()));
-    index_writer.add_document(doc!(title => "The Diary of a Young Girl", price => 20_120u64, date => DateTime::from_str("2018-04-09T00:00:00+00:00").unwrap()));
-    assert!(index_writer.commit().is_ok());
-
-    let reader = index.reader().unwrap();
-    let searcher = reader.searcher();
-
-    let query_parser = QueryParser::for_index(&index, vec![title]);
-    let query = query_parser.parse_query("diary").unwrap();
-    let filter_some_collector = FilterCollector::new(
-        price,
-        &|value: u64| value > 20_120u64,
-        TopDocs::with_limit(2),
-    );
-    let top_docs = searcher.search(&query, &filter_some_collector).unwrap();
-
-    assert_eq!(top_docs.len(), 1);
-    assert_eq!(top_docs[0].1, DocAddress(0, 1));
-
-    let filter_all_collector: FilterCollector<_, _, u64> =
-        FilterCollector::new(price, &|value| value < 5u64, TopDocs::with_limit(2));
-    let filtered_top_docs = searcher.search(&query, &filter_all_collector).unwrap();
-
-    assert_eq!(filtered_top_docs.len(), 0);
-
-    fn date_filter(value: DateTime) -> bool {
-        (value - DateTime::from_str("2019-04-09T00:00:00+00:00").unwrap()).num_weeks() > 0
-    }
-
-    let filter_dates_collector = FilterCollector::new(date, &date_filter, TopDocs::with_limit(5));
-    let filtered_date_docs = searcher.search(&query, &filter_dates_collector).unwrap();
-
-    assert_eq!(filtered_date_docs.len(), 2);
-}
-
 /// Stores all of the doc ids.
 /// This collector is only used for tests.
 /// It is unusable in pr
@@ -240,15 +185,12 @@ impl Collector for BytesFastFieldTestCollector {
         _segment_local_id: u32,
         segment_reader: &SegmentReader,
     ) -> crate::Result<BytesFastFieldSegmentCollector> {
-        let reader = segment_reader
-            .fast_fields()
-            .bytes(self.field)
-            .ok_or_else(|| {
-                crate::TantivyError::InvalidArgument("Field is not a bytes fast field.".to_string())
-            })?;
         Ok(BytesFastFieldSegmentCollector {
             vals: Vec::new(),
-            reader,
+            reader: segment_reader
+                .fast_fields()
+                .bytes(self.field)
+                .expect("Field is not a bytes fast field."),
         })
     }
 
@@ -264,7 +206,7 @@ impl Collector for BytesFastFieldTestCollector {
 impl SegmentCollector for BytesFastFieldSegmentCollector {
     type Fruit = Vec<u8>;
 
-    fn collect(&mut self, doc: u32, _score: Score) {
+    fn collect(&mut self, doc: u32, _score: f32) {
         let data = self.reader.get_bytes(doc);
         self.vals.extend(data);
     }

src/collector/top_collector.rs

@@ -18,9 +18,9 @@ use std::collections::BinaryHeap;
 /// Two elements are equal if their feature is equal, and regardless of whether `doc`
 /// is equal. This should be perfectly fine for this usage, but let's make sure this
 /// struct is never public.
-pub(crate) struct ComparableDoc<T, D> {
+struct ComparableDoc<T, D> {
-    pub feature: T,
+    feature: T,
-    pub doc: D,
+    doc: D,
 }
 
 impl<T: PartialOrd, D: PartialOrd> PartialOrd for ComparableDoc<T, D> {
@@ -56,8 +56,7 @@ impl<T: PartialOrd, D: PartialOrd> PartialEq for ComparableDoc<T, D> {
 impl<T: PartialOrd, D: PartialOrd> Eq for ComparableDoc<T, D> {}
 
 pub(crate) struct TopCollector<T> {
-    pub limit: usize,
+    limit: usize,
-    pub offset: usize,
     _marker: PhantomData<T>,
 }
 
@@ -73,20 +72,14 @@ where
         if limit < 1 {
             panic!("Limit must be strictly greater than 0.");
         }
-        Self {
+        TopCollector {
             limit,
-            offset: 0,
             _marker: PhantomData,
         }
     }
 
-    /// Skip the first "offset" documents when collecting.
+    pub fn limit(&self) -> usize {
-    ///
+        self.limit
-    /// This is equivalent to `OFFSET` in MySQL or PostgreSQL and `start` in
-    /// Lucene's TopDocsCollector.
-    pub fn and_offset(mut self, offset: usize) -> TopCollector<T> {
-        self.offset = offset;
-        self
     }
 
     pub fn merge_fruits(
@@ -99,7 +92,7 @@ where
         let mut top_collector = BinaryHeap::new();
         for child_fruit in children {
             for (feature, doc) in child_fruit {
-                if top_collector.len() < (self.limit + self.offset) {
+                if top_collector.len() < self.limit {
                     top_collector.push(ComparableDoc { feature, doc });
                 } else if let Some(mut head) = top_collector.peek_mut() {
                     if head.feature < feature {
@@ -111,7 +104,6 @@ where
         Ok(top_collector
             .into_sorted_vec()
             .into_iter()
-            .skip(self.offset)
             .map(|cdoc| (cdoc.feature, cdoc.doc))
             .collect())
     }
@@ -121,23 +113,7 @@ where
         segment_id: SegmentLocalId,
         _: &SegmentReader,
     ) -> crate::Result<TopSegmentCollector<F>> {
-        Ok(TopSegmentCollector::new(
+        Ok(TopSegmentCollector::new(segment_id, self.limit))
-            segment_id,
-            self.limit + self.offset,
-        ))
-    }
-
-    /// Create a new TopCollector with the same limit and offset.
-    ///
-    /// Ideally we would use Into but the blanket implementation seems to cause the Scorer traits
-    /// to fail.
-    #[doc(hidden)]
-    pub(crate) fn into_tscore<TScore: PartialOrd + Clone>(self) -> TopCollector<TScore> {
-        TopCollector {
-            limit: self.limit,
-            offset: self.offset,
-            _marker: PhantomData,
-        }
     }
 }
 
@@ -211,7 +187,7 @@ impl<T: PartialOrd + Clone> TopSegmentCollector<T> {
 
 #[cfg(test)]
 mod tests {
-    use super::{TopCollector, TopSegmentCollector};
+    use super::TopSegmentCollector;
     use crate::DocAddress;
 
     #[test]
@@ -272,48 +248,6 @@ mod tests {
             top_collector_limit_3.harvest()[..2].to_vec(),
         );
     }
-
-    #[test]
-    fn test_top_collector_with_limit_and_offset() {
-        let collector = TopCollector::with_limit(2).and_offset(1);
-
-        let results = collector
-            .merge_fruits(vec![vec![
-                (0.9, DocAddress(0, 1)),
-                (0.8, DocAddress(0, 2)),
-                (0.7, DocAddress(0, 3)),
-                (0.6, DocAddress(0, 4)),
-                (0.5, DocAddress(0, 5)),
-            ]])
-            .unwrap();
-
-        assert_eq!(
-            results,
-            vec![(0.8, DocAddress(0, 2)), (0.7, DocAddress(0, 3)),]
-        );
-    }
-
-    #[test]
-    fn test_top_collector_with_limit_larger_than_set_and_offset() {
-        let collector = TopCollector::with_limit(2).and_offset(1);
-
-        let results = collector
-            .merge_fruits(vec![vec![(0.9, DocAddress(0, 1)), (0.8, DocAddress(0, 2))]])
-            .unwrap();
-
-        assert_eq!(results, vec![(0.8, DocAddress(0, 2)),]);
-    }
-
-    #[test]
-    fn test_top_collector_with_limit_and_offset_larger_than_set() {
-        let collector = TopCollector::with_limit(2).and_offset(20);
-
-        let results = collector
-            .merge_fruits(vec![vec![(0.9, DocAddress(0, 1)), (0.8, DocAddress(0, 2))]])
-            .unwrap();
-
-        assert_eq!(results, vec![]);
-    }
 }
 
 #[cfg(all(test, feature = "unstable"))]

src/collector/top_score_collector.rs

@@ -1,82 +1,19 @@
 use super::Collector;
-use crate::collector::top_collector::{ComparableDoc, TopCollector};
+use crate::collector::custom_score_top_collector::CustomScoreTopCollector;
+use crate::collector::top_collector::TopCollector;
+use crate::collector::top_collector::TopSegmentCollector;
 use crate::collector::tweak_score_top_collector::TweakedScoreTopCollector;
 use crate::collector::{
     CustomScorer, CustomSegmentScorer, ScoreSegmentTweaker, ScoreTweaker, SegmentCollector,
 };
 use crate::fastfield::FastFieldReader;
-use crate::query::Weight;
 use crate::schema::Field;
 use crate::DocAddress;
 use crate::DocId;
 use crate::Score;
 use crate::SegmentLocalId;
 use crate::SegmentReader;
-use crate::{collector::custom_score_top_collector::CustomScoreTopCollector, fastfield::FastValue};
-use crate::{collector::top_collector::TopSegmentCollector, TantivyError};
 use std::fmt;
-use std::{collections::BinaryHeap, marker::PhantomData};
-
-struct FastFieldConvertCollector<
-    TCollector: Collector<Fruit = Vec<(u64, DocAddress)>>,
-    TFastValue: FastValue,
-> {
-    pub collector: TCollector,
-    pub field: Field,
-    pub fast_value: std::marker::PhantomData<TFastValue>,
-}
-
-impl<TCollector, TFastValue> Collector for FastFieldConvertCollector<TCollector, TFastValue>
-where
-    TCollector: Collector<Fruit = Vec<(u64, DocAddress)>>,
-    TFastValue: FastValue + 'static,
-{
-    type Fruit = Vec<(TFastValue, DocAddress)>;
-
-    type Child = TCollector::Child;
-
-    fn for_segment(
-        &self,
-        segment_local_id: crate::SegmentLocalId,
-        segment: &SegmentReader,
-    ) -> crate::Result<Self::Child> {
-        let schema = segment.schema();
-        let field_entry = schema.get_field_entry(self.field);
-        if !field_entry.is_fast() {
-            return Err(TantivyError::SchemaError(format!(
-                "Field {:?} is not a fast field.",
-                field_entry.name()
-            )));
-        }
-        let schema_type = TFastValue::to_type();
-        let requested_type = field_entry.field_type().value_type();
-        if schema_type != requested_type {
-            return Err(TantivyError::SchemaError(format!(
-                "Field {:?} is of type {:?}!={:?}",
-                field_entry.name(),
-                schema_type,
-                requested_type
-            )));
-        }
-        self.collector.for_segment(segment_local_id, segment)
-    }
-
-    fn requires_scoring(&self) -> bool {
-        self.collector.requires_scoring()
-    }
-
-    fn merge_fruits(
-        &self,
-        segment_fruits: Vec<<Self::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<Self::Fruit> {
-        let raw_result = self.collector.merge_fruits(segment_fruits)?;
-        let transformed_result = raw_result
-            .into_iter()
-            .map(|(score, doc_address)| (TFastValue::from_u64(score), doc_address))
-            .collect::<Vec<_>>();
-        Ok(transformed_result)
-    }
-}
 
 /// The `TopDocs` collector keeps track of the top `K` documents
 /// sorted by their score.
@@ -99,7 +36,7 @@ where
 /// let schema = schema_builder.build();
 /// let index = Index::create_in_ram(schema);
 ///
-/// let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
+/// let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
 /// index_writer.add_document(doc!(title => "The Name of the Wind"));
 /// index_writer.add_document(doc!(title => "The Diary of Muadib"));
 /// index_writer.add_document(doc!(title => "A Dairy Cow"));
@@ -113,18 +50,14 @@ where
 /// let query = query_parser.parse_query("diary").unwrap();
 /// let top_docs = searcher.search(&query, &TopDocs::with_limit(2)).unwrap();
 ///
-/// assert_eq!(top_docs[0].1, DocAddress(0, 1));
+/// assert_eq!(&top_docs[0], &(0.7261542, DocAddress(0, 1)));
-/// assert_eq!(top_docs[1].1, DocAddress(0, 3));
+/// assert_eq!(&top_docs[1], &(0.6099695, DocAddress(0, 3)));
 /// ```
 pub struct TopDocs(TopCollector<Score>);
 
 impl fmt::Debug for TopDocs {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
+        write!(f, "TopDocs({})", self.0.limit())
-            f,
-            "TopDocs(limit={}, offset={})",
-            self.0.limit, self.0.offset
-        )
     }
 }
 
@@ -133,8 +66,8 @@ struct ScorerByFastFieldReader {
 }
 
 impl CustomSegmentScorer<u64> for ScorerByFastFieldReader {
-    fn score(&mut self, doc: DocId) -> u64 {
+    fn score(&self, doc: DocId) -> u64 {
-        self.ff_reader.get(doc)
+        self.ff_reader.get_u64(u64::from(doc))
     }
 }
 
@@ -148,10 +81,10 @@ impl CustomScorer<u64> for ScorerByField {
     fn segment_scorer(&self, segment_reader: &SegmentReader) -> crate::Result<Self::Child> {
         let ff_reader = segment_reader
             .fast_fields()
-            .u64_lenient(self.field)
+            .u64(self.field)
             .ok_or_else(|| {
                 crate::TantivyError::SchemaError(format!(
-                    "Field requested ({:?}) is not a fast field.",
+                    "Field requested ({:?}) is not a i64/u64 fast field.",
                     self.field
                 ))
             })?;
@@ -168,57 +101,8 @@ impl TopDocs {
         TopDocs(TopCollector::with_limit(limit))
     }
 
-    /// Skip the first "offset" documents when collecting.
-    ///
-    /// This is equivalent to `OFFSET` in MySQL or PostgreSQL and `start` in
-    /// Lucene's TopDocsCollector.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// use tantivy::collector::TopDocs;
-    /// use tantivy::query::QueryParser;
-    /// use tantivy::schema::{Schema, TEXT};
-    /// use tantivy::{doc, DocAddress, Index};
-    ///
-    /// let mut schema_builder = Schema::builder();
-    /// let title = schema_builder.add_text_field("title", TEXT);
-    /// let schema = schema_builder.build();
-    /// let index = Index::create_in_ram(schema);
-    ///
-    /// let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
-    /// index_writer.add_document(doc!(title => "The Name of the Wind"));
-    /// index_writer.add_document(doc!(title => "The Diary of Muadib"));
-    /// index_writer.add_document(doc!(title => "A Dairy Cow"));
-    /// index_writer.add_document(doc!(title => "The Diary of a Young Girl"));
-    /// index_writer.add_document(doc!(title => "The Diary of Lena Mukhina"));
-    /// assert!(index_writer.commit().is_ok());
-    ///
-    /// let reader = index.reader().unwrap();
-    /// let searcher = reader.searcher();
-    ///
-    /// let query_parser = QueryParser::for_index(&index, vec![title]);
-    /// let query = query_parser.parse_query("diary").unwrap();
-    /// let top_docs = searcher.search(&query, &TopDocs::with_limit(2).and_offset(1)).unwrap();
-    ///
-    /// assert_eq!(top_docs.len(), 2);
-    /// assert_eq!(top_docs[0].1, DocAddress(0, 4));
-    /// assert_eq!(top_docs[1].1, DocAddress(0, 3));
-    /// ```
-    pub fn and_offset(self, offset: usize) -> TopDocs {
-        TopDocs(self.0.and_offset(offset))
-    }
-
     /// Set top-K to rank documents by a given fast field.
     ///
-    /// If the field is not a fast or does not exist, this method returns successfully (it is not aware of any schema).
-    /// An error will be returned at the moment of search.
-    ///
-    /// If the field is a FAST field but not a u64 field, search will return successfully but it will return
-    /// returns a monotonic u64-representation (ie. the order is still correct) of the requested field type.
-    ///
-    /// # Example
-    ///
     /// ```rust
     /// # use tantivy::schema::{Schema, FAST, TEXT};
     /// # use tantivy::{doc, Index, DocAddress};
@@ -234,13 +118,13 @@ impl TopDocs {
     /// #   let schema = schema_builder.build();
     /// #  
     /// #   let index = Index::create_in_ram(schema);
-    /// #   let mut index_writer = index.writer_with_num_threads(1, 10_000_000)?;
+    /// #   let mut index_writer = index.writer_with_num_threads(1, 3_000_000)?;
     /// #   index_writer.add_document(doc!(title => "The Name of the Wind", rating => 92u64));
     /// #   index_writer.add_document(doc!(title => "The Diary of Muadib", rating => 97u64));
     /// #   index_writer.add_document(doc!(title => "A Dairy Cow", rating => 63u64));
     /// #   index_writer.add_document(doc!(title => "The Diary of a Young Girl", rating => 80u64));
     /// #   assert!(index_writer.commit().is_ok());
-    /// #   let reader = index.reader()?;
+    /// #   let reader = index.reader().unwrap();
     /// #   let query = QueryParser::for_index(&index, vec![title]).parse_query("diary")?;
     /// #   let top_docs = docs_sorted_by_rating(&reader.searcher(), &query, rating)?;
     /// #   assert_eq!(top_docs,
@@ -248,20 +132,25 @@ impl TopDocs {
     /// #                 (80u64, DocAddress(0u32, 3))]);
     /// #   Ok(())
     /// # }
+    ///
+    ///
     /// /// Searches the document matching the given query, and
     /// /// collects the top 10 documents, order by the u64-`field`
     /// /// given in argument.
+    /// ///
+    /// /// `field` is required to be a FAST field.
     /// fn docs_sorted_by_rating(searcher: &Searcher,
     ///                          query: &dyn Query,
-    ///                          rating_field: Field)
+    ///                          sort_by_field: Field)
     ///     -> tantivy::Result<Vec<(u64, DocAddress)>> {
     ///
     ///     // This is where we build our topdocs collector
     ///     //
-    ///     // Note the `rating_field` needs to be a FAST field here.
+    ///     // Note the generics parameter that needs to match the
-    ///     let top_books_by_rating = TopDocs
+    ///     // type `sort_by_field`.
+    ///     let top_docs_by_rating = TopDocs
     ///                 ::with_limit(10)
-    ///                  .order_by_u64_field(rating_field);
+    ///                  .order_by_u64_field(sort_by_field);
     ///     
     ///     // ... and here are our documents. Note this is a simple vec.
     ///     // The `u64` in the pair is the value of our fast field for
@@ -271,105 +160,21 @@ impl TopDocs {
     ///     // length of 10, or less if not enough documents matched the
     ///     // query.
     ///     let resulting_docs: Vec<(u64, DocAddress)> =
-    ///          searcher.search(query, &top_books_by_rating)?;
+    ///          searcher.search(query, &top_docs_by_rating)?;
     ///     
     ///     Ok(resulting_docs)
     /// }
     /// ```
     ///
-    /// # See also
+    /// # Panics
-    ///  
+    ///
-    /// To confortably work with `u64`s, `i64`s, `f64`s, or `date`s, please refer to
+    /// May panic if the field requested is not a fast field.
-    /// [.order_by_fast_field(...)](#method.order_by_fast_field) method.
+    ///
     pub fn order_by_u64_field(
         self,
         field: Field,
     ) -> impl Collector<Fruit = Vec<(u64, DocAddress)>> {
-        CustomScoreTopCollector::new(ScorerByField { field }, self.0.into_tscore())
+        self.custom_score(ScorerByField { field })
-    }
-
-    /// Set top-K to rank documents by a given fast field.
-    ///
-    /// If the field is not a fast field, or its field type does not match the generic type, this method does not panic,  
-    /// but an explicit error will be returned at the moment of collection.
-    ///
-    /// Note that this method is a generic. The requested fast field type will be often
-    /// inferred in your code by the rust compiler.
-    ///
-    /// Implementation-wise, for performance reason, tantivy will manipulate the u64 representation of your fast
-    /// field until the last moment.
-    ///
-    /// # Example
-    ///
-    /// ```rust
-    /// # use tantivy::schema::{Schema, FAST, TEXT};
-    /// # use tantivy::{doc, Index, DocAddress};
-    /// # use tantivy::query::{Query, AllQuery};
-    /// use tantivy::Searcher;
-    /// use tantivy::collector::TopDocs;
-    /// use tantivy::schema::Field;
-    ///
-    /// # fn main() -> tantivy::Result<()> {
-    /// #   let mut schema_builder = Schema::builder();
-    /// #   let title = schema_builder.add_text_field("company", TEXT);
-    /// #   let rating = schema_builder.add_i64_field("revenue", FAST);
-    /// #   let schema = schema_builder.build();
-    /// #  
-    /// #   let index = Index::create_in_ram(schema);
-    /// #   let mut index_writer = index.writer_with_num_threads(1, 10_000_000)?;
-    /// #   index_writer.add_document(doc!(title => "MadCow Inc.", rating => 92_000_000i64));
-    /// #   index_writer.add_document(doc!(title => "Zozo Cow KKK", rating => 119_000_000i64));
-    /// #   index_writer.add_document(doc!(title => "Declining Cow", rating => -63_000_000i64));
-    /// #   assert!(index_writer.commit().is_ok());
-    /// #   let reader = index.reader()?;
-    /// #   let top_docs = docs_sorted_by_revenue(&reader.searcher(), &AllQuery, rating)?;
-    /// #   assert_eq!(top_docs,
-    /// #            vec![(119_000_000i64, DocAddress(0, 1)),
-    /// #                 (92_000_000i64, DocAddress(0, 0))]);
-    /// #   Ok(())
-    /// # }
-    /// /// Searches the document matching the given query, and
-    /// /// collects the top 10 documents, order by the u64-`field`
-    /// /// given in argument.
-    /// fn docs_sorted_by_revenue(searcher: &Searcher,
-    ///                          query: &dyn Query,
-    ///                          revenue_field: Field)
-    ///     -> tantivy::Result<Vec<(i64, DocAddress)>> {
-    ///
-    ///     // This is where we build our topdocs collector
-    ///     //
-    ///     // Note the generics parameter that needs to match the
-    ///     // type `sort_by_field`. revenue_field here is a FAST i64 field.
-    ///     let top_company_by_revenue = TopDocs
-    ///                 ::with_limit(2)
-    ///                  .order_by_fast_field(revenue_field);
-    ///     
-    ///     // ... and here are our documents. Note this is a simple vec.
-    ///     // The `i64` in the pair is the value of our fast field for
-    ///     // each documents.
-    ///     //
-    ///     // The vec is sorted decreasingly by `sort_by_field`, and has a
-    ///     // length of 10, or less if not enough documents matched the
-    ///     // query.
-    ///     let resulting_docs: Vec<(i64, DocAddress)> =
-    ///          searcher.search(query, &top_company_by_revenue)?;
-    ///     
-    ///     Ok(resulting_docs)
-    /// }
-    /// ```
-    pub fn order_by_fast_field<TFastValue>(
-        self,
-        fast_field: Field,
-    ) -> impl Collector<Fruit = Vec<(TFastValue, DocAddress)>>
-    where
-        TFastValue: FastValue + 'static,
-    {
-        let u64_collector = self.order_by_u64_field(fast_field);
-        FastFieldConvertCollector {
-            collector: u64_collector,
-            field: fast_field,
-            fast_value: PhantomData,
-        }
     }
 
     /// Ranks the documents using a custom score.
@@ -414,7 +219,7 @@ impl TopDocs {
     /// fn create_index() -> tantivy::Result<Index> {
     ///   let schema = create_schema();
     ///   let index = Index::create_in_ram(schema);
-    ///   let mut index_writer = index.writer_with_num_threads(1, 10_000_000)?;
+    ///   let mut index_writer = index.writer_with_num_threads(1, 3_000_000)?;
     ///   let product_name = index.schema().get_field("product_name").unwrap();
     ///   let popularity: Field = index.schema().get_field("popularity").unwrap();
     ///   index_writer.add_document(doc!(product_name => "The Diary of Muadib", popularity => 1u64));
@@ -453,7 +258,7 @@ impl TopDocs {
     ///                 let popularity: u64 = popularity_reader.get(doc);
     ///                 // Well.. For the sake of the example we use a simple logarithm
     ///                 // function.
-    ///                 let popularity_boost_score = ((2u64 + popularity) as Score).log2();
+    ///                 let popularity_boost_score = ((2u64 + popularity) as f32).log2();
     ///                 popularity_boost_score * original_score
     ///             }
     ///           });
@@ -474,9 +279,9 @@ impl TopDocs {
     where
         TScore: 'static + Send + Sync + Clone + PartialOrd,
         TScoreSegmentTweaker: ScoreSegmentTweaker<TScore> + 'static,
-        TScoreTweaker: ScoreTweaker<TScore, Child = TScoreSegmentTweaker> + Send + Sync,
+        TScoreTweaker: ScoreTweaker<TScore, Child = TScoreSegmentTweaker>,
     {
-        TweakedScoreTopCollector::new(score_tweaker, self.0.into_tscore())
+        TweakedScoreTopCollector::new(score_tweaker, self.0.limit())
     }
 
     /// Ranks the documents using a custom score.
@@ -521,7 +326,7 @@ impl TopDocs {
     /// # fn main() -> tantivy::Result<()> {
     /// #   let schema = create_schema();
     /// #   let index = Index::create_in_ram(schema);
-    /// #   let mut index_writer = index.writer_with_num_threads(1, 10_000_000)?;
+    /// #   let mut index_writer = index.writer_with_num_threads(1, 3_000_000)?;
     /// #   let product_name = index.schema().get_field("product_name").unwrap();
     /// #   
     /// let popularity: Field = index.schema().get_field("popularity").unwrap();
@@ -588,9 +393,9 @@ impl TopDocs {
     where
         TScore: 'static + Send + Sync + Clone + PartialOrd,
         TCustomSegmentScorer: CustomSegmentScorer<TScore> + 'static,
-        TCustomScorer: CustomScorer<TScore, Child = TCustomSegmentScorer> + Send + Sync,
+        TCustomScorer: CustomScorer<TScore, Child = TCustomSegmentScorer>,
     {
-        CustomScoreTopCollector::new(custom_score, self.0.into_tscore())
+        CustomScoreTopCollector::new(custom_score, self.0.limit())
     }
 }
 
@@ -618,64 +423,6 @@ impl Collector for TopDocs {
     ) -> crate::Result<Self::Fruit> {
         self.0.merge_fruits(child_fruits)
     }
-
-    fn collect_segment(
-        &self,
-        weight: &dyn Weight,
-        segment_ord: u32,
-        reader: &SegmentReader,
-    ) -> crate::Result<<Self::Child as SegmentCollector>::Fruit> {
-        let heap_len = self.0.limit + self.0.offset;
-        let mut heap: BinaryHeap<ComparableDoc<Score, DocId>> = BinaryHeap::with_capacity(heap_len);
-
-        if let Some(delete_bitset) = reader.delete_bitset() {
-            let mut threshold = Score::MIN;
-            weight.for_each_pruning(threshold, reader, &mut |doc, score| {
-                if delete_bitset.is_deleted(doc) {
-                    return threshold;
-                }
-                let heap_item = ComparableDoc {
-                    feature: score,
-                    doc,
-                };
-                if heap.len() < heap_len {
-                    heap.push(heap_item);
-                    if heap.len() == heap_len {
-                        threshold = heap.peek().map(|el| el.feature).unwrap_or(Score::MIN);
-                    }
-                    return threshold;
-                }
-                *heap.peek_mut().unwrap() = heap_item;
-                threshold = heap.peek().map(|el| el.feature).unwrap_or(Score::MIN);
-                threshold
-            })?;
-        } else {
-            weight.for_each_pruning(Score::MIN, reader, &mut |doc, score| {
-                let heap_item = ComparableDoc {
-                    feature: score,
-                    doc,
-                };
-                if heap.len() < heap_len {
-                    heap.push(heap_item);
-                    // TODO the threshold is suboptimal for heap.len == heap_len
-                    if heap.len() == heap_len {
-                        return heap.peek().map(|el| el.feature).unwrap_or(Score::MIN);
-                    } else {
-                        return Score::MIN;
-                    }
-                }
-                *heap.peek_mut().unwrap() = heap_item;
-                heap.peek().map(|el| el.feature).unwrap_or(Score::MIN)
-            })?;
-        }
-
-        let fruit = heap
-            .into_sorted_vec()
-            .into_iter()
-            .map(|cid| (cid.feature, DocAddress(segment_ord, cid.doc)))
-            .collect();
-        Ok(fruit)
-    }
 }
 
 /// Segment Collector associated to `TopDocs`.
@@ -685,7 +432,7 @@ impl SegmentCollector for TopScoreSegmentCollector {
     type Fruit = Vec<(Score, DocAddress)>;
 
     fn collect(&mut self, doc: DocId, score: Score) {
-        self.0.collect(doc, score);
+        self.0.collect(doc, score)
     }
 
     fn harvest(self) -> Vec<(Score, DocAddress)> {
@@ -699,10 +446,10 @@ mod tests {
     use crate::collector::Collector;
     use crate::query::{AllQuery, Query, QueryParser};
     use crate::schema::{Field, Schema, FAST, STORED, TEXT};
+    use crate::DocAddress;
     use crate::Index;
     use crate::IndexWriter;
     use crate::Score;
-    use crate::{DocAddress, DocId, SegmentReader};
 
     fn make_index() -> Index {
         let mut schema_builder = Schema::builder();
@@ -711,7 +458,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
         {
             // writing the segment
-            let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.add_document(doc!(text_field=>"Hello happy tax payer."));
             index_writer.add_document(doc!(text_field=>"Droopy says hello happy tax payer"));
             index_writer.add_document(doc!(text_field=>"I like Droopy"));
@@ -720,15 +467,8 @@ mod tests {
         index
     }
 
-    fn assert_results_equals(results: &[(Score, DocAddress)], expected: &[(Score, DocAddress)]) {
-        for (result, expected) in results.iter().zip(expected.iter()) {
-            assert_eq!(result.1, expected.1);
-            crate::assert_nearly_equals!(result.0, expected.0);
-        }
-    }
-
     #[test]
-    fn test_top_collector_not_at_capacity_without_offset() {
+    fn test_top_collector_not_at_capacity() {
         let index = make_index();
         let field = index.schema().get_field("text").unwrap();
         let query_parser = QueryParser::for_index(&index, vec![field]);
@@ -739,31 +479,16 @@ mod tests {
             .searcher()
             .search(&text_query, &TopDocs::with_limit(4))
             .unwrap();
-        assert_results_equals(
+        assert_eq!(
-            &score_docs,
+            score_docs,
-            &[
+            vec![
                 (0.81221175, DocAddress(0u32, 1)),
                 (0.5376842, DocAddress(0u32, 2)),
-                (0.48527452, DocAddress(0, 0)),
+                (0.48527452, DocAddress(0, 0))
-            ],
+            ]
         );
     }
 
-    #[test]
-    fn test_top_collector_not_at_capacity_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let score_docs: Vec<(Score, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &TopDocs::with_limit(4).and_offset(2))
-            .unwrap();
-        assert_results_equals(&score_docs[..], &[(0.48527452, DocAddress(0, 0))]);
-    }
-
     #[test]
     fn test_top_collector_at_capacity() {
         let index = make_index();
@@ -776,33 +501,12 @@ mod tests {
             .searcher()
             .search(&text_query, &TopDocs::with_limit(2))
             .unwrap();
-        assert_results_equals(
+        assert_eq!(
-            &score_docs,
+            score_docs,
-            &[
+            vec![
                 (0.81221175, DocAddress(0u32, 1)),
                 (0.5376842, DocAddress(0u32, 2)),
-            ],
+            ]
-        );
-    }
-
-    #[test]
-    fn test_top_collector_at_capacity_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let score_docs: Vec<(Score, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &TopDocs::with_limit(2).and_offset(1))
-            .unwrap();
-        assert_results_equals(
-            &score_docs[..],
-            &[
-                (0.5376842, DocAddress(0u32, 2)),
-                (0.48527452, DocAddress(0, 0)),
-            ],
         );
     }
 
@@ -863,8 +567,8 @@ mod tests {
         let top_collector = TopDocs::with_limit(4).order_by_u64_field(size);
         let top_docs: Vec<(u64, DocAddress)> = searcher.search(&query, &top_collector).unwrap();
         assert_eq!(
-            &top_docs[..],
+            top_docs,
-            &[
+            vec![
                 (64, DocAddress(0, 1)),
                 (16, DocAddress(0, 2)),
                 (12, DocAddress(0, 0))
@@ -872,94 +576,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn test_top_field_collector_datetime() -> crate::Result<()> {
-        use std::str::FromStr;
-        let mut schema_builder = Schema::builder();
-        let name = schema_builder.add_text_field("name", TEXT);
-        let birthday = schema_builder.add_date_field("birthday", FAST);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        let pr_birthday = crate::DateTime::from_str("1898-04-09T00:00:00+00:00")?;
-        index_writer.add_document(doc!(
-            name => "Paul Robeson",
-            birthday => pr_birthday
-        ));
-        let mr_birthday = crate::DateTime::from_str("1947-11-08T00:00:00+00:00")?;
-        index_writer.add_document(doc!(
-            name => "Minnie Riperton",
-            birthday => mr_birthday
-        ));
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let top_collector = TopDocs::with_limit(3).order_by_fast_field(birthday);
-        let top_docs: Vec<(crate::DateTime, DocAddress)> =
-            searcher.search(&AllQuery, &top_collector)?;
-        assert_eq!(
-            &top_docs[..],
-            &[
-                (mr_birthday, DocAddress(0, 1)),
-                (pr_birthday, DocAddress(0, 0)),
-            ]
-        );
-        Ok(())
-    }
-
-    #[test]
-    fn test_top_field_collector_i64() -> crate::Result<()> {
-        let mut schema_builder = Schema::builder();
-        let city = schema_builder.add_text_field("city", TEXT);
-        let altitude = schema_builder.add_i64_field("altitude", FAST);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(
-                city => "georgetown",
-                altitude =>  -1i64,
-        ));
-        index_writer.add_document(doc!(
-            city => "tokyo",
-            altitude =>  40i64,
-        ));
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let top_collector = TopDocs::with_limit(3).order_by_fast_field(altitude);
-        let top_docs: Vec<(i64, DocAddress)> = searcher.search(&AllQuery, &top_collector)?;
-        assert_eq!(
-            &top_docs[..],
-            &[(40i64, DocAddress(0, 1)), (-1i64, DocAddress(0, 0)),]
-        );
-        Ok(())
-    }
-
-    #[test]
-    fn test_top_field_collector_f64() -> crate::Result<()> {
-        let mut schema_builder = Schema::builder();
-        let city = schema_builder.add_text_field("city", TEXT);
-        let altitude = schema_builder.add_f64_field("altitude", FAST);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(
-                city => "georgetown",
-                altitude =>  -1.0f64,
-        ));
-        index_writer.add_document(doc!(
-            city => "tokyo",
-            altitude =>  40f64,
-        ));
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let top_collector = TopDocs::with_limit(3).order_by_fast_field(altitude);
-        let top_docs: Vec<(f64, DocAddress)> = searcher.search(&AllQuery, &top_collector)?;
-        assert_eq!(
-            &top_docs[..],
-            &[(40f64, DocAddress(0, 1)), (-1.0f64, DocAddress(0, 0)),]
-        );
-        Ok(())
-    }
-
     #[test]
     #[should_panic]
     fn test_field_does_not_exist() {
@@ -982,85 +598,29 @@ mod tests {
     }
 
     #[test]
-    fn test_field_not_fast_field() -> crate::Result<()> {
+    fn test_field_not_fast_field() {
         let mut schema_builder = Schema::builder();
+        let title = schema_builder.add_text_field(TITLE, TEXT);
         let size = schema_builder.add_u64_field(SIZE, STORED);
         let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
+        let (index, _) = index("beer", title, schema, |index_writer| {
-        let mut index_writer = index.writer_for_tests()?;
+            index_writer.add_document(doc!(
-        index_writer.add_document(doc!(size=>1u64));
+                title => "bottle of beer",
-        index_writer.commit()?;
+                size => 12u64,
-        let searcher = index.reader()?.searcher();
+            ));
+        });
+        let searcher = index.reader().unwrap().searcher();
         let segment = searcher.segment_reader(0);
         let top_collector = TopDocs::with_limit(4).order_by_u64_field(size);
-        let err = top_collector.for_segment(0, segment).err().unwrap();
+        let err = top_collector.for_segment(0, segment);
-        assert!(
+        if let Err(crate::TantivyError::SchemaError(msg)) = err {
-            matches!(err, crate::TantivyError::SchemaError(msg) if msg == "Field requested (Field(0)) is not a fast field.")
+            assert_eq!(
-        );
+                msg,
-        Ok(())
+                "Field requested (Field(1)) is not a i64/u64 fast field."
-    }
+            );
-
+        } else {
-    #[test]
+            assert!(false);
-    fn test_field_wrong_type() -> crate::Result<()> {
+        }
-        let mut schema_builder = Schema::builder();
-        let size = schema_builder.add_u64_field(SIZE, STORED);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(size=>1u64));
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let segment = searcher.segment_reader(0);
-        let top_collector = TopDocs::with_limit(4).order_by_fast_field::<i64>(size);
-        let err = top_collector.for_segment(0, segment).err().unwrap();
-        assert!(
-            matches!(err, crate::TantivyError::SchemaError(msg) if msg == "Field \"size\" is not a fast field.")
-        );
-        Ok(())
-    }
-
-    #[test]
-    fn test_tweak_score_top_collector_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let collector = TopDocs::with_limit(2).and_offset(1).tweak_score(
-            move |_segment_reader: &SegmentReader| move |doc: DocId, _original_score: Score| doc,
-        );
-        let score_docs: Vec<(u32, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &collector)
-            .unwrap();
-
-        assert_eq!(
-            score_docs,
-            vec![(1, DocAddress(0, 1)), (0, DocAddress(0, 0)),]
-        );
-    }
-
-    #[test]
-    fn test_custom_score_top_collector_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let collector = TopDocs::with_limit(2)
-            .and_offset(1)
-            .custom_score(move |_segment_reader: &SegmentReader| move |doc: DocId| doc);
-        let score_docs: Vec<(u32, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &collector)
-            .unwrap();
-
-        assert_eq!(
-            score_docs,
-            vec![(1, DocAddress(0, 1)), (0, DocAddress(0, 0)),]
-        );
     }
 
     fn index(
@@ -1070,7 +630,8 @@ mod tests {
         mut doc_adder: impl FnMut(&mut IndexWriter) -> (),
     ) -> (Index, Box<dyn Query>) {
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
+
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         doc_adder(&mut index_writer);
         index_writer.commit().unwrap();
         let query_parser = QueryParser::for_index(&index, vec![query_field]);

src/collector/tweak_score_top_collector.rs

@@ -14,11 +14,11 @@ where
 {
     pub fn new(
         score_tweaker: TScoreTweaker,
-        collector: TopCollector<TScore>,
+        limit: usize,
     ) -> TweakedScoreTopCollector<TScoreTweaker, TScore> {
         TweakedScoreTopCollector {
             score_tweaker,
-            collector,
+            collector: TopCollector::with_limit(limit),
         }
     }
 }
@@ -29,7 +29,7 @@ where
 /// It is the segment local version of the [`ScoreTweaker`](./trait.ScoreTweaker.html).
 pub trait ScoreSegmentTweaker<TScore>: 'static {
     /// Tweak the given `score` for the document `doc`.
-    fn score(&mut self, doc: DocId, score: Score) -> TScore;
+    fn score(&self, doc: DocId, score: Score) -> TScore;
 }
 
 /// `ScoreTweaker` makes it possible to tweak the score
@@ -49,7 +49,7 @@ pub trait ScoreTweaker<TScore>: Sync {
 
 impl<TScoreTweaker, TScore> Collector for TweakedScoreTopCollector<TScoreTweaker, TScore>
 where
-    TScoreTweaker: ScoreTweaker<TScore> + Send + Sync,
+    TScoreTweaker: ScoreTweaker<TScore>,
     TScore: 'static + PartialOrd + Clone + Send + Sync,
 {
     type Fruit = Vec<(TScore, DocAddress)>;
@@ -121,9 +121,9 @@ where
 
 impl<F, TScore> ScoreSegmentTweaker<TScore> for F
 where
-    F: 'static + FnMut(DocId, Score) -> TScore,
+    F: 'static + Sync + Send + Fn(DocId, Score) -> TScore,
 {
-    fn score(&mut self, doc: DocId, score: Score) -> TScore {
+    fn score(&self, doc: DocId, score: Score) -> TScore {
         (self)(doc, score)
     }
 }

src/common/bitpacker.rs

@@ -1,7 +1,6 @@
 use byteorder::{ByteOrder, LittleEndian, WriteBytesExt};
 use std::io;
-
+use std::ops::Deref;
-use crate::directory::OwnedBytes;
 
 pub(crate) struct BitPacker {
     mini_buffer: u64,
@@ -61,14 +60,20 @@ impl BitPacker {
 }
 
 #[derive(Clone)]
-pub struct BitUnpacker {
+pub struct BitUnpacker<Data>
+where
+    Data: Deref<Target = [u8]>,
+{
     num_bits: u64,
     mask: u64,
-    data: OwnedBytes,
+    data: Data,
 }
 
-impl BitUnpacker {
+impl<Data> BitUnpacker<Data>
-    pub fn new(data: OwnedBytes, num_bits: u8) -> BitUnpacker {
+where
+    Data: Deref<Target = [u8]>,
+{
+    pub fn new(data: Data, num_bits: u8) -> BitUnpacker<Data> {
         let mask: u64 = if num_bits == 64 {
             !0u64
         } else {
@@ -85,7 +90,7 @@ impl BitUnpacker {
         if self.num_bits == 0 {
             return 0u64;
         }
-        let data: &[u8] = self.data.as_slice();
+        let data: &[u8] = &*self.data;
         let num_bits = self.num_bits;
         let mask = self.mask;
         let addr_in_bits = idx * num_bits;
@@ -104,9 +109,8 @@ impl BitUnpacker {
 #[cfg(test)]
 mod test {
     use super::{BitPacker, BitUnpacker};
-    use crate::directory::OwnedBytes;
 
-    fn create_fastfield_bitpacker(len: usize, num_bits: u8) -> (BitUnpacker, Vec<u64>) {
+    fn create_fastfield_bitpacker(len: usize, num_bits: u8) -> (BitUnpacker<Vec<u8>>, Vec<u64>) {
         let mut data = Vec::new();
         let mut bitpacker = BitPacker::new();
         let max_val: u64 = (1u64 << num_bits as u64) - 1u64;
@@ -118,7 +122,7 @@ mod test {
         }
         bitpacker.close(&mut data).unwrap();
         assert_eq!(data.len(), ((num_bits as usize) * len + 7) / 8 + 7);
-        let bitunpacker = BitUnpacker::new(OwnedBytes::new(data), num_bits);
+        let bitunpacker = BitUnpacker::new(data, num_bits);
         (bitunpacker, vals)
     }
 

src/common/bitset.rs

@@ -33,10 +33,6 @@ impl TinySet {
         TinySet(0u64)
     }
 
-    pub fn clear(&mut self) {
-        self.0 = 0u64;
-    }
-
     /// Returns the complement of the set in `[0, 64[`.
     fn complement(self) -> TinySet {
         TinySet(!self.0)
@@ -47,11 +43,6 @@ impl TinySet {
         !self.intersect(TinySet::singleton(el)).is_empty()
     }
 
-    /// Returns the number of elements in the TinySet.
-    pub fn len(self) -> u32 {
-        self.0.count_ones()
-    }
-
     /// Returns the intersection of `self` and `other`
     pub fn intersect(self, other: TinySet) -> TinySet {
         TinySet(self.0 & other.0)
@@ -118,12 +109,22 @@ impl TinySet {
     pub fn range_greater_or_equal(from_included: u32) -> TinySet {
         TinySet::range_lower(from_included).complement()
     }
+
+    pub fn clear(&mut self) {
+        self.0 = 0u64;
+    }
+
+    pub fn len(self) -> u32 {
+        self.0.count_ones()
+    }
 }
 
 #[derive(Clone)]
 pub struct BitSet {
     tinysets: Box<[TinySet]>,
-    len: usize,
+    len: usize, //< Technically it should be u32, but we
+    // count multiple inserts.
+    // `usize` guards us from overflow.
     max_value: u32,
 }
 
@@ -203,7 +204,7 @@ mod tests {
 
     use super::BitSet;
     use super::TinySet;
-    use crate::docset::{DocSet, TERMINATED};
+    use crate::docset::DocSet;
     use crate::query::BitSetDocSet;
     use crate::tests;
     use crate::tests::generate_nonunique_unsorted;
@@ -277,13 +278,11 @@ mod tests {
         }
         assert_eq!(btreeset.len(), bitset.len());
         let mut bitset_docset = BitSetDocSet::from(bitset);
-        let mut remaining = true;
         for el in btreeset.into_iter() {
-            assert!(remaining);
+            bitset_docset.advance();
             assert_eq!(bitset_docset.doc(), el);
-            remaining = bitset_docset.advance() != TERMINATED;
         }
-        assert!(!remaining);
+        assert!(!bitset_docset.advance());
     }
 
     #[test]

src/common/composite_file.rs

@@ -1,15 +1,14 @@
 use crate::common::BinarySerializable;
 use crate::common::CountingWriter;
 use crate::common::VInt;
-use crate::directory::FileSlice;
+use crate::directory::ReadOnlySource;
 use crate::directory::{TerminatingWrite, WritePtr};
 use crate::schema::Field;
 use crate::space_usage::FieldUsage;
 use crate::space_usage::PerFieldSpaceUsage;
 use std::collections::HashMap;
-use std::io::{self, Read, Write};
+use std::io::Write;
-
+use std::io::{self, Read};
-use super::HasLen;
 
 #[derive(Eq, PartialEq, Hash, Copy, Ord, PartialOrd, Clone, Debug)]
 pub struct FileAddr {
@@ -104,26 +103,25 @@ impl<W: TerminatingWrite + Write> CompositeWrite<W> {
 /// for each field.
 #[derive(Clone)]
 pub struct CompositeFile {
-    data: FileSlice,
+    data: ReadOnlySource,
     offsets_index: HashMap<FileAddr, (usize, usize)>,
 }
 
 impl CompositeFile {
     /// Opens a composite file stored in a given
-    /// `FileSlice`.
+    /// `ReadOnlySource`.
-    pub fn open(data: &FileSlice) -> io::Result<CompositeFile> {
+    pub fn open(data: &ReadOnlySource) -> io::Result<CompositeFile> {
         let end = data.len();
-        let footer_len_data = data.slice_from(end - 4).read_bytes()?;
+        let footer_len_data = data.slice_from(end - 4);
         let footer_len = u32::deserialize(&mut footer_len_data.as_slice())? as usize;
         let footer_start = end - 4 - footer_len;
-        let footer_data = data
+        let footer_data = data.slice(footer_start, footer_start + footer_len);
-            .slice(footer_start, footer_start + footer_len)
-            .read_bytes()?;
         let mut footer_buffer = footer_data.as_slice();
         let num_fields = VInt::deserialize(&mut footer_buffer)?.0 as usize;
 
         let mut file_addrs = vec![];
         let mut offsets = vec![];
+
         let mut field_index = HashMap::new();
 
         let mut offset = 0;
@@ -152,19 +150,19 @@ impl CompositeFile {
     pub fn empty() -> CompositeFile {
         CompositeFile {
             offsets_index: HashMap::new(),
-            data: FileSlice::empty(),
+            data: ReadOnlySource::empty(),
         }
     }
 
-    /// Returns the `FileSlice` associated
+    /// Returns the `ReadOnlySource` associated
     /// to a given `Field` and stored in a `CompositeFile`.
-    pub fn open_read(&self, field: Field) -> Option<FileSlice> {
+    pub fn open_read(&self, field: Field) -> Option<ReadOnlySource> {
         self.open_read_with_idx(field, 0)
     }
 
-    /// Returns the `FileSlice` associated
+    /// Returns the `ReadOnlySource` associated
     /// to a given `Field` and stored in a `CompositeFile`.
-    pub fn open_read_with_idx(&self, field: Field, idx: usize) -> Option<FileSlice> {
+    pub fn open_read_with_idx(&self, field: Field, idx: usize) -> Option<ReadOnlySource> {
         self.offsets_index
             .get(&FileAddr { field, idx })
             .map(|&(from, to)| self.data.slice(from, to))
@@ -192,46 +190,49 @@ mod test {
     use crate::schema::Field;
     use std::io::Write;
     use std::path::Path;
+    
 
     #[test]
-    fn test_composite_file() -> crate::Result<()> {
+    fn test_composite_file() {
         let path = Path::new("test_path");
-        let directory = RAMDirectory::create();
+        let mut directory = RAMDirectory::default();
         {
             let w = directory.open_write(path).unwrap();
             let mut composite_write = CompositeWrite::wrap(w);
-            let mut write_0 = composite_write.for_field(Field::from_field_id(0u32));
+            {
-            VInt(32431123u64).serialize(&mut write_0)?;
+                let mut write_0 = composite_write.for_field(Field::from_field_id(0u32));
-            write_0.flush()?;
+                VInt(32431123u64).serialize(&mut write_0).unwrap();
-            let mut write_4 = composite_write.for_field(Field::from_field_id(4u32));
+                write_0.flush().unwrap();
-            VInt(2).serialize(&mut write_4)?;
+            }
-            write_4.flush()?;
+
-            composite_write.close()?;
+            {
+                let mut write_4 = composite_write.for_field(Field::from_field_id(4u32));
+                VInt(2).serialize(&mut write_4).unwrap();
+                write_4.flush().unwrap();
+            }
+            composite_write.close().unwrap();
         }
         {
-            let r = directory.open_read(path)?;
+            let r = directory.open_read(path).unwrap();
-            let composite_file = CompositeFile::open(&r)?;
+            let composite_file = CompositeFile::open(&r).unwrap();
             {
                 let file0 = composite_file
                     .open_read(Field::from_field_id(0u32))
-                    .unwrap()
+                    .unwrap();
-                    .read_bytes()?;
                 let mut file0_buf = file0.as_slice();
-                let payload_0 = VInt::deserialize(&mut file0_buf)?.0;
+                let payload_0 = VInt::deserialize(&mut file0_buf).unwrap().0;
                 assert_eq!(file0_buf.len(), 0);
                 assert_eq!(payload_0, 32431123u64);
             }
             {
                 let file4 = composite_file
                     .open_read(Field::from_field_id(4u32))
-                    .unwrap()
+                    .unwrap();
-                    .read_bytes()?;
                 let mut file4_buf = file4.as_slice();
-                let payload_4 = VInt::deserialize(&mut file4_buf)?.0;
+                let payload_4 = VInt::deserialize(&mut file4_buf).unwrap().0;
                 assert_eq!(file4_buf.len(), 0);
                 assert_eq!(payload_4, 2u64);
             }
         }
-        Ok(())
     }
 }

src/common/counting_writer.rs

@@ -20,10 +20,9 @@ impl<W: Write> CountingWriter<W> {
         self.written_bytes
     }
 
-    /// Returns the underlying write object.
+    pub fn finish(mut self) -> io::Result<(W, u64)> {
-    /// Note that this method does not trigger any flushing.
+        self.flush()?;
-    pub fn finish(self) -> W {
+        Ok((self.underlying, self.written_bytes))
-        self.underlying
     }
 }
 
@@ -47,6 +46,7 @@ impl<W: Write> Write for CountingWriter<W> {
 
 impl<W: TerminatingWrite> TerminatingWrite for CountingWriter<W> {
     fn terminate_ref(&mut self, token: AntiCallToken) -> io::Result<()> {
+        self.flush()?;
         self.underlying.terminate_ref(token)
     }
 }
@@ -63,9 +63,8 @@ mod test {
         let mut counting_writer = CountingWriter::wrap(buffer);
         let bytes = (0u8..10u8).collect::<Vec<u8>>();
         counting_writer.write_all(&bytes).unwrap();
-        let len = counting_writer.written_bytes();
+        let (w, len): (Vec<u8>, u64) = counting_writer.finish().unwrap();
-        let buffer_restituted: Vec<u8> = counting_writer.finish();
         assert_eq!(len, 10u64);
-        assert_eq!(buffer_restituted.len(), 10);
+        assert_eq!(w.len(), 10);
     }
 }

src/common/mod.rs

@@ -2,6 +2,7 @@ pub mod bitpacker;
 mod bitset;
 mod composite_file;
 mod counting_writer;
+mod mutable_enum;
 mod serialize;
 mod vint;
 
@@ -9,10 +10,9 @@ pub use self::bitset::BitSet;
 pub(crate) use self::bitset::TinySet;
 pub(crate) use self::composite_file::{CompositeFile, CompositeWrite};
 pub use self::counting_writer::CountingWriter;
+pub(crate) use self::mutable_enum::MutableEnum;
 pub use self::serialize::{BinarySerializable, FixedSize};
-pub use self::vint::{
+pub use self::vint::{read_u32_vint, serialize_vint_u32, write_u32_vint, VInt};
-    read_u32_vint, read_u32_vint_no_advance, serialize_vint_u32, write_u32_vint, VInt,
-};
 pub use byteorder::LittleEndian as Endianness;
 
 /// Segment's max doc must be `< MAX_DOC_LIMIT`.
@@ -66,6 +66,10 @@ pub(crate) fn compute_num_bits(n: u64) -> u8 {
     }
 }
 
+pub(crate) fn is_power_of_2(n: usize) -> bool {
+    (n > 0) && (n & (n - 1) == 0)
+}
+
 /// Has length trait
 pub trait HasLen {
     /// Return length
@@ -115,16 +119,11 @@ pub fn u64_to_i64(val: u64) -> i64 {
 /// For simplicity, tantivy internally handles `f64` as `u64`.
 /// The mapping is defined by this function.
 ///
-/// Maps `f64` to `u64` in a monotonic manner, so that bytes lexical order is preserved.
+/// Maps `f64` to `u64` so that lexical order is preserved.
 ///
 /// This is more suited than simply casting (`val as u64`)
 /// which would truncate the result
 ///
-/// # Reference
-///
-/// Daniel Lemire's [blog post](https://lemire.me/blog/2020/12/14/converting-floating-point-numbers-to-integers-while-preserving-order/)
-/// explains the mapping in a clear manner.
-///
 /// # See also
 /// The [reverse mapping is `u64_to_f64`](./fn.u64_to_f64.html).
 #[inline(always)]
@@ -153,7 +152,6 @@ pub(crate) mod test {
     pub use super::minmax;
     pub use super::serialize::test::fixed_size_test;
     use super::{compute_num_bits, f64_to_u64, i64_to_u64, u64_to_f64, u64_to_i64};
-    use proptest::prelude::*;
     use std::f64;
 
     fn test_i64_converter_helper(val: i64) {
@@ -164,15 +162,6 @@ pub(crate) mod test {
         assert_eq!(u64_to_f64(f64_to_u64(val)), val);
     }
 
-    proptest! {
-        #[test]
-        fn test_f64_converter_monotonicity_proptest((left, right) in (proptest::num::f64::NORMAL, proptest::num::f64::NORMAL)) {
-            let left_u64 = f64_to_u64(left);
-            let right_u64 = f64_to_u64(right);
-            assert_eq!(left_u64 < right_u64,  left < right);
-        }
-    }
-
     #[test]
     fn test_i64_converter() {
         assert_eq!(i64_to_u64(i64::min_value()), u64::min_value());

src/common/mutable_enum.rs

@@ -0,0 +1,37 @@
+use std::ops::{Deref, DerefMut};
+
+pub(crate) struct MutableEnum<T>(Option<T>);
+
+impl<T> MutableEnum<T> {
+    pub fn wrap(val: T) -> Self {
+        MutableEnum(Some(val))
+    }
+
+    pub fn into(self) -> T {
+        self.0.unwrap()
+    }
+}
+
+impl<T> MutableEnum<T> {
+    pub fn map_mutate<E, F>(&mut self, transformation: F) -> Result<(), E>
+    where
+        F: FnOnce(T) -> Result<T, E>,
+    {
+        self.0 = self.0.take().map(transformation).transpose()?;
+        Ok(())
+    }
+}
+
+impl<T> Deref for MutableEnum<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        self.0.as_ref().unwrap()
+    }
+}
+
+impl<T> DerefMut for MutableEnum<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.0.as_mut().unwrap()
+    }
+}

src/common/serialize.rs

@@ -89,19 +89,6 @@ impl FixedSize for u64 {
     const SIZE_IN_BYTES: usize = 8;
 }
 
-impl BinarySerializable for f32 {
-    fn serialize<W: Write>(&self, writer: &mut W) -> io::Result<()> {
-        writer.write_f32::<Endianness>(*self)
-    }
-    fn deserialize<R: Read>(reader: &mut R) -> io::Result<Self> {
-        reader.read_f32::<Endianness>()
-    }
-}
-
-impl FixedSize for f32 {
-    const SIZE_IN_BYTES: usize = 4;
-}
-
 impl BinarySerializable for i64 {
     fn serialize<W: Write>(&self, writer: &mut W) -> io::Result<()> {
         writer.write_i64::<Endianness>(*self)

src/common/vint.rs

@@ -5,12 +5,12 @@ use std::io::Read;
 use std::io::Write;
 
 ///   Wrapper over a `u64` that serializes as a variable int.
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[derive(Debug, Eq, PartialEq)]
 pub struct VInt(pub u64);
 
 const STOP_BIT: u8 = 128;
 
-pub fn serialize_vint_u32(val: u32, buf: &mut [u8; 8]) -> &[u8] {
+pub fn serialize_vint_u32(val: u32) -> (u64, usize) {
     const START_2: u64 = 1 << 7;
     const START_3: u64 = 1 << 14;
     const START_4: u64 = 1 << 21;
@@ -29,7 +29,7 @@ pub fn serialize_vint_u32(val: u32, buf: &mut [u8; 8]) -> &[u8] {
 
     let val = u64::from(val);
     const STOP_BIT: u64 = 128u64;
-    let (res, num_bytes) = match val {
+    match val {
         0..=STOP_1 => (val | STOP_BIT, 1),
         START_2..=STOP_2 => (
             (val & MASK_1) | ((val & MASK_2) << 1) | (STOP_BIT << (8)),
@@ -56,9 +56,7 @@ pub fn serialize_vint_u32(val: u32, buf: &mut [u8; 8]) -> &[u8] {
                 | (STOP_BIT << (8 * 4)),
             5,
         ),
-    };
+    }
-    LittleEndian::write_u64(&mut buf[..], res);
-    &buf[0..num_bytes]
 }
 
 /// Returns the number of bytes covered by a
@@ -87,26 +85,23 @@ fn vint_len(data: &[u8]) -> usize {
 /// If the buffer does not start by a valid
 /// vint payload
 pub fn read_u32_vint(data: &mut &[u8]) -> u32 {
-    let (result, vlen) = read_u32_vint_no_advance(*data);
+    let vlen = vint_len(*data);
-    *data = &data[vlen..];
-    result
-}
-
-pub fn read_u32_vint_no_advance(data: &[u8]) -> (u32, usize) {
-    let vlen = vint_len(data);
     let mut result = 0u32;
     let mut shift = 0u64;
     for &b in &data[..vlen] {
         result |= u32::from(b & 127u8) << shift;
         shift += 7;
     }
-    (result, vlen)
+    *data = &data[vlen..];
+    result
 }
+
 /// Write a `u32` as a vint payload.
 pub fn write_u32_vint<W: io::Write>(val: u32, writer: &mut W) -> io::Result<()> {
-    let mut buf = [0u8; 8];
+    let (val, num_bytes) = serialize_vint_u32(val);
-    let data = serialize_vint_u32(val, &mut buf);
+    let mut buffer = [0u8; 8];
-    writer.write_all(&data)
+    LittleEndian::write_u64(&mut buffer, val);
+    writer.write_all(&buffer[..num_bytes])
 }
 
 impl VInt {
@@ -177,6 +172,7 @@ mod tests {
     use super::serialize_vint_u32;
     use super::VInt;
     use crate::common::BinarySerializable;
+    use byteorder::{ByteOrder, LittleEndian};
 
     fn aux_test_vint(val: u64) {
         let mut v = [14u8; 10];
@@ -212,10 +208,12 @@ mod tests {
 
     fn aux_test_serialize_vint_u32(val: u32) {
         let mut buffer = [0u8; 10];
-        let mut buffer2 = [0u8; 8];
+        let mut buffer2 = [0u8; 10];
         let len_vint = VInt(val as u64).serialize_into(&mut buffer);
-        let res2 = serialize_vint_u32(val, &mut buffer2);
+        let (vint, len) = serialize_vint_u32(val);
-        assert_eq!(&buffer[..len_vint], res2, "array wrong for {}", val);
+        assert_eq!(len, len_vint, "len wrong for val {}", val);
+        LittleEndian::write_u64(&mut buffer2, vint);
+        assert_eq!(&buffer[..len], &buffer2[..len], "array wrong for {}", val);
     }
 
     #[test]

src/core/index.rs

@@ -5,7 +5,6 @@ use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::core::SegmentMetaInventory;
 use crate::core::META_FILEPATH;
-use crate::directory::error::OpenReadError;
 use crate::directory::ManagedDirectory;
 #[cfg(feature = "mmap")]
 use crate::directory::MmapDirectory;
@@ -13,8 +12,8 @@ use crate::directory::INDEX_WRITER_LOCK;
 use crate::directory::{Directory, RAMDirectory};
 use crate::error::DataCorruption;
 use crate::error::TantivyError;
-use crate::indexer::index_writer::HEAP_SIZE_MIN;
 use crate::indexer::segment_updater::save_new_metas;
+use crate::indexer::IndexWriterConfig;
 use crate::reader::IndexReader;
 use crate::reader::IndexReaderBuilder;
 use crate::schema::Field;
@@ -22,12 +21,12 @@ use crate::schema::FieldType;
 use crate::schema::Schema;
 use crate::tokenizer::{TextAnalyzer, TokenizerManager};
 use crate::IndexWriter;
+use num_cpus;
+use std::borrow::BorrowMut;
 use std::collections::HashSet;
 use std::fmt;
-
 #[cfg(feature = "mmap")]
-use std::path::Path;
+use std::path::{Path, PathBuf};
-use std::path::PathBuf;
 use std::sync::Arc;
 
 fn load_metas(
@@ -35,18 +34,12 @@ fn load_metas(
     inventory: &SegmentMetaInventory,
 ) -> crate::Result<IndexMeta> {
     let meta_data = directory.atomic_read(&META_FILEPATH)?;
-    let meta_string = String::from_utf8(meta_data)
+    let meta_string = String::from_utf8_lossy(&meta_data);
-        .map_err(|utf8_err| {
-            DataCorruption::new(
-                META_FILEPATH.to_path_buf(),
-                format!("Meta file is not valid utf-8. {:?}", utf8_err)
-            )
-        })?;
     IndexMeta::deserialize(&meta_string, &inventory)
         .map_err(|e| {
             DataCorruption::new(
                 META_FILEPATH.to_path_buf(),
-                format!("Meta file cannot be deserialized. {:?}. content = {}", e, meta_string),
+                format!("Meta file cannot be deserialized. {:?}.", e),
             )
         })
         .map_err(From::from)
@@ -63,10 +56,8 @@ pub struct Index {
 }
 
 impl Index {
-    /// Examines the directory to see if it contains an index.
+    /// Examines the director to see if it contains an index
-    ///
+    pub fn exists<Dir: Directory>(dir: &Dir) -> bool {
-    /// Effectively, it only checks for the presence of the `meta.json` file.
-    pub fn exists<Dir: Directory>(dir: &Dir) -> Result<bool, OpenReadError> {
         dir.exists(&META_FILEPATH)
     }
 
@@ -113,7 +104,7 @@ impl Index {
         schema: Schema,
     ) -> crate::Result<Index> {
         let mmap_directory = MmapDirectory::open(directory_path)?;
-        if Index::exists(&mmap_directory)? {
+        if Index::exists(&mmap_directory) {
             return Err(TantivyError::IndexAlreadyExists);
         }
         Index::create(mmap_directory, schema)
@@ -121,7 +112,7 @@ impl Index {
 
     /// Opens or creates a new index in the provided directory
     pub fn open_or_create<Dir: Directory>(dir: Dir, schema: Schema) -> crate::Result<Index> {
-        if !Index::exists(&dir)? {
+        if !Index::exists(&dir) {
             return Index::create(dir, schema);
         }
         let index = Index::open(dir)?;
@@ -148,9 +139,7 @@ impl Index {
         Index::create(mmap_directory, schema)
     }
 
-    /// Creates a new index given an implementation of the trait `Directory`.
+    /// Creates a new index given an implementation of the trait `Directory`
-    ///
-    /// If a directory previously existed, it will be erased.
     pub fn create<Dir: Directory>(dir: Dir, schema: Schema) -> crate::Result<Index> {
         let directory = ManagedDirectory::wrap(dir)?;
         Index::from_directory(directory, schema)
@@ -159,8 +148,8 @@ impl Index {
     /// Create a new index from a directory.
     ///
     /// This will overwrite existing meta.json
-    fn from_directory(directory: ManagedDirectory, schema: Schema) -> crate::Result<Index> {
+    fn from_directory(mut directory: ManagedDirectory, schema: Schema) -> crate::Result<Index> {
-        save_new_metas(schema.clone(), &directory)?;
+        save_new_metas(schema.clone(), directory.borrow_mut())?;
         let metas = IndexMeta::with_schema(schema);
         Index::create_from_metas(directory, &metas, SegmentMetaInventory::default())
     }
@@ -284,8 +273,40 @@ impl Index {
     pub fn writer_with_num_threads(
         &self,
         num_threads: usize,
-        overall_heap_size_in_bytes: usize,
+        overall_heap_size_in_bytes: u64,
     ) -> crate::Result<IndexWriter> {
+        let config = IndexWriterConfig {
+            max_indexing_threads: num_threads,
+            memory_budget: overall_heap_size_in_bytes,
+            ..Default::default()
+        };
+        self.writer_from_config(config)
+    }
+
+    /// Creates a multithreaded writer
+    ///
+    /// Tantivy will automatically define the number of threads to use.
+    /// `overall_heap_size_in_bytes` is the total target memory usage that will be split
+    /// between a given number of threads.
+    ///
+    /// # Errors
+    /// If the lockfile already exists, returns `Error::FileAlreadyExists`.
+    /// # Panics
+    /// If the heap size per thread is too small, panics.
+    pub fn writer(&self, overall_heap_size_in_bytes: u64) -> crate::Result<IndexWriter> {
+        let config = IndexWriterConfig {
+            max_indexing_threads: num_cpus::get(),
+            memory_budget: overall_heap_size_in_bytes,
+            ..Default::default()
+        };
+        self.writer_from_config(config)
+    }
+
+    /// Creates a new writer with a given configuration.
+    ///
+    /// See [`IndexWriterConfig`](./struct.IndexWriterConfig.html) for more information.
+    pub fn writer_from_config(&self, mut config: IndexWriterConfig) -> crate::Result<IndexWriter> {
+        config.validate()?;
         let directory_lock = self
             .directory
             .acquire_lock(&INDEX_WRITER_LOCK)
@@ -301,41 +322,7 @@ impl Index {
                     ),
                 )
             })?;
-        let heap_size_in_bytes_per_thread = overall_heap_size_in_bytes / num_threads;
+        IndexWriter::new(self, config, directory_lock)
-        IndexWriter::new(
-            self,
-            num_threads,
-            heap_size_in_bytes_per_thread,
-            directory_lock,
-        )
-    }
-
-    /// Helper to create an index writer for tests.
-    ///
-    /// That index writer only simply has a single thread and a heap of 5 MB.
-    /// Using a single thread gives us a deterministic allocation of DocId.
-    #[cfg(test)]
-    pub fn writer_for_tests(&self) -> crate::Result<IndexWriter> {
-        self.writer_with_num_threads(1, 10_000_000)
-    }
-
-    /// Creates a multithreaded writer
-    ///
-    /// Tantivy will automatically define the number of threads to use.
-    /// `overall_heap_size_in_bytes` is the total target memory usage that will be split
-    /// between a given number of threads.
-    ///
-    /// # Errors
-    /// If the lockfile already exists, returns `Error::FileAlreadyExists`.
-    /// # Panics
-    /// If the heap size per thread is too small, panics.
-    pub fn writer(&self, overall_heap_size_in_bytes: usize) -> crate::Result<IndexWriter> {
-        let mut num_threads = num_cpus::get();
-        let heap_size_in_bytes_per_thread = overall_heap_size_in_bytes / num_threads;
-        if heap_size_in_bytes_per_thread < HEAP_SIZE_MIN {
-            num_threads = (overall_heap_size_in_bytes / HEAP_SIZE_MIN).max(1);
-        }
-        self.writer_with_num_threads(num_threads, overall_heap_size_in_bytes)
     }
 
     /// Accessor to the index schema
@@ -406,7 +393,7 @@ impl fmt::Debug for Index {
 
 #[cfg(test)]
 mod tests {
-    use crate::directory::{RAMDirectory, WatchCallback};
+    use crate::directory::RAMDirectory;
     use crate::schema::Field;
     use crate::schema::{Schema, INDEXED, TEXT};
     use crate::IndexReader;
@@ -430,24 +417,24 @@ mod tests {
     #[test]
     fn test_index_exists() {
         let directory = RAMDirectory::create();
-        assert!(!Index::exists(&directory).unwrap());
+        assert!(!Index::exists(&directory));
         assert!(Index::create(directory.clone(), throw_away_schema()).is_ok());
-        assert!(Index::exists(&directory).unwrap());
+        assert!(Index::exists(&directory));
     }
 
     #[test]
     fn open_or_create_should_create() {
         let directory = RAMDirectory::create();
-        assert!(!Index::exists(&directory).unwrap());
+        assert!(!Index::exists(&directory));
         assert!(Index::open_or_create(directory.clone(), throw_away_schema()).is_ok());
-        assert!(Index::exists(&directory).unwrap());
+        assert!(Index::exists(&directory));
     }
 
     #[test]
     fn open_or_create_should_open() {
         let directory = RAMDirectory::create();
         assert!(Index::create(directory.clone(), throw_away_schema()).is_ok());
-        assert!(Index::exists(&directory).unwrap());
+        assert!(Index::exists(&directory));
         assert!(Index::open_or_create(directory, throw_away_schema()).is_ok());
     }
 
@@ -455,7 +442,7 @@ mod tests {
     fn create_should_wipeoff_existing() {
         let directory = RAMDirectory::create();
         assert!(Index::create(directory.clone(), throw_away_schema()).is_ok());
-        assert!(Index::exists(&directory).unwrap());
+        assert!(Index::exists(&directory));
         assert!(Index::create(directory.clone(), Schema::builder().build()).is_ok());
     }
 
@@ -463,7 +450,7 @@ mod tests {
     fn open_or_create_exists_but_schema_does_not_match() {
         let directory = RAMDirectory::create();
         assert!(Index::create(directory.clone(), throw_away_schema()).is_ok());
-        assert!(Index::exists(&directory).unwrap());
+        assert!(Index::exists(&directory));
         assert!(Index::open_or_create(directory.clone(), throw_away_schema()).is_ok());
         let err = Index::open_or_create(directory, Schema::builder().build());
         assert_eq!(
@@ -489,7 +476,7 @@ mod tests {
             .try_into()
             .unwrap();
         assert_eq!(reader.searcher().num_docs(), 0);
-        test_index_on_commit_reload_policy_aux(field, &index, &reader);
+        test_index_on_commit_reload_policy_aux(field, index.clone(), &index, &reader);
     }
 
     #[cfg(feature = "mmap")]
@@ -513,32 +500,32 @@ mod tests {
                 .try_into()
                 .unwrap();
             assert_eq!(reader.searcher().num_docs(), 0);
-            test_index_on_commit_reload_policy_aux(field, &index, &reader);
+            test_index_on_commit_reload_policy_aux(field, index.clone(), &index, &reader);
         }
 
         #[test]
-        fn test_index_manual_policy_mmap() -> crate::Result<()> {
+        fn test_index_manual_policy_mmap() {
             let schema = throw_away_schema();
             let field = schema.get_field("num_likes").unwrap();
-            let mut index = Index::create_from_tempdir(schema)?;
+            let mut index = Index::create_from_tempdir(schema).unwrap();
-            let mut writer = index.writer_for_tests()?;
+            let mut writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-            writer.commit()?;
+            writer.commit().unwrap();
             let reader = index
                 .reader_builder()
                 .reload_policy(ReloadPolicy::Manual)
-                .try_into()?;
+                .try_into()
+                .unwrap();
             assert_eq!(reader.searcher().num_docs(), 0);
             writer.add_document(doc!(field=>1u64));
             let (sender, receiver) = crossbeam::channel::unbounded();
-            let _handle = index.directory_mut().watch(WatchCallback::new(move || {
+            let _handle = index.directory_mut().watch(Box::new(move || {
                 let _ = sender.send(());
             }));
-            writer.commit()?;
+            writer.commit().unwrap();
             assert!(receiver.recv().is_ok());
             assert_eq!(reader.searcher().num_docs(), 0);
-            reader.reload()?;
+            reader.reload().unwrap();
             assert_eq!(reader.searcher().num_docs(), 1);
-            Ok(())
         }
 
         #[test]
@@ -555,38 +542,30 @@ mod tests {
                 .try_into()
                 .unwrap();
             assert_eq!(reader.searcher().num_docs(), 0);
-            test_index_on_commit_reload_policy_aux(field, &write_index, &reader);
+            test_index_on_commit_reload_policy_aux(field, read_index, &write_index, &reader);
         }
     }
-    fn test_index_on_commit_reload_policy_aux(field: Field, index: &Index, reader: &IndexReader) {
+
-        let mut reader_index = reader.index();
+    fn test_index_on_commit_reload_policy_aux(
+        field: Field,
+        mut reader_index: Index,
+        index: &Index,
+        reader: &IndexReader,
+    ) {
         let (sender, receiver) = crossbeam::channel::unbounded();
-        let _watch_handle = reader_index
+        let _watch_handle = reader_index.directory_mut().watch(Box::new(move || {
-            .directory_mut()
+            let _ = sender.send(());
-            .watch(WatchCallback::new(move || {
+        }));
-                let _ = sender.send(());
+        let mut writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-            }));
-        let mut writer = index.writer_for_tests().unwrap();
         assert_eq!(reader.searcher().num_docs(), 0);
         writer.add_document(doc!(field=>1u64));
         writer.commit().unwrap();
-        // We need a loop here because it is possible for notify to send more than
+        assert!(receiver.recv().is_ok());
-        // one modify event. It was observed on CI on MacOS.
+        assert_eq!(reader.searcher().num_docs(), 1);
-        loop {
-            assert!(receiver.recv().is_ok());
-            if reader.searcher().num_docs() == 1 {
-                break;
-            }
-        }
         writer.add_document(doc!(field=>2u64));
         writer.commit().unwrap();
-        // ... Same as above
+        assert!(receiver.recv().is_ok());
-        loop {
+        assert_eq!(reader.searcher().num_docs(), 2);
-            assert!(receiver.recv().is_ok());
-            if reader.searcher().num_docs() == 2 {
-                break;
-            }
-        }
     }
 
     // This test will not pass on windows, because windows
@@ -604,7 +583,7 @@ mod tests {
             writer.add_document(doc!(field => i));
         }
         let (sender, receiver) = crossbeam::channel::unbounded();
-        let _handle = directory.watch(WatchCallback::new(move || {
+        let _handle = directory.watch(Box::new(move || {
             let _ = sender.send(());
         }));
         writer.commit().unwrap();

src/core/index_meta.rs

@@ -3,7 +3,9 @@ use crate::core::SegmentId;
 use crate::schema::Schema;
 use crate::Opstamp;
 use census::{Inventory, TrackedObject};
+use serde;
 use serde::{Deserialize, Serialize};
+use serde_json;
 use std::collections::HashSet;
 use std::fmt;
 use std::path::PathBuf;
@@ -213,7 +215,7 @@ pub struct IndexMeta {
     #[serde(skip_serializing_if = "Option::is_none")]
     /// Payload associated to the last commit.
     ///
-    /// Upon commit, clients can optionally add a small `String` payload to their commit
+    /// Upon commit, clients can optionally add a small `Striing` payload to their commit
     /// to help identify this commit.
     /// This payload is entirely unused by tantivy.
     pub payload: Option<String>,

src/core/inverted_index_reader.rs

@@ -1,13 +1,13 @@
-use std::io;
-
 use crate::common::BinarySerializable;
-use crate::directory::FileSlice;
+use crate::directory::ReadOnlySource;
 use crate::positions::PositionReader;
 use crate::postings::TermInfo;
 use crate::postings::{BlockSegmentPostings, SegmentPostings};
+use crate::schema::FieldType;
 use crate::schema::IndexRecordOption;
 use crate::schema::Term;
 use crate::termdict::TermDictionary;
+use owned_read::OwnedRead;
 
 /// The inverted index reader is in charge of accessing
 /// the inverted index associated to a specific field.
@@ -16,7 +16,7 @@ use crate::termdict::TermDictionary;
 ///
 /// It is safe to delete the segment associated to
 /// an `InvertedIndexReader`. As long as it is open,
-/// the `FileSlice` it is relying on should
+/// the `ReadOnlySource` it is relying on should
 /// stay available.
 ///
 ///
@@ -24,9 +24,9 @@ use crate::termdict::TermDictionary;
 /// the `SegmentReader`'s [`.inverted_index(...)`] method
 pub struct InvertedIndexReader {
     termdict: TermDictionary,
-    postings_file_slice: FileSlice,
+    postings_source: ReadOnlySource,
-    positions_file_slice: FileSlice,
+    positions_source: ReadOnlySource,
-    positions_idx_file_slice: FileSlice,
+    positions_idx_source: ReadOnlySource,
     record_option: IndexRecordOption,
     total_num_tokens: u64,
 }
@@ -35,38 +35,42 @@ impl InvertedIndexReader {
     #[cfg_attr(feature = "cargo-clippy", allow(clippy::needless_pass_by_value))] // for symmetry
     pub(crate) fn new(
         termdict: TermDictionary,
-        postings_file_slice: FileSlice,
+        postings_source: ReadOnlySource,
-        positions_file_slice: FileSlice,
+        positions_source: ReadOnlySource,
-        positions_idx_file_slice: FileSlice,
+        positions_idx_source: ReadOnlySource,
         record_option: IndexRecordOption,
-    ) -> io::Result<InvertedIndexReader> {
+    ) -> InvertedIndexReader {
-        let (total_num_tokens_slice, postings_body) = postings_file_slice.split(8);
+        let total_num_tokens_data = postings_source.slice(0, 8);
-        let total_num_tokens = u64::deserialize(&mut total_num_tokens_slice.read_bytes()?)?;
+        let mut total_num_tokens_cursor = total_num_tokens_data.as_slice();
-        Ok(InvertedIndexReader {
+        let total_num_tokens = u64::deserialize(&mut total_num_tokens_cursor).unwrap_or(0u64);
+        InvertedIndexReader {
             termdict,
-            postings_file_slice: postings_body,
+            postings_source: postings_source.slice_from(8),
-            positions_file_slice,
+            positions_source,
-            positions_idx_file_slice,
+            positions_idx_source,
             record_option,
             total_num_tokens,
-        })
+        }
     }
 
     /// Creates an empty `InvertedIndexReader` object, which
     /// contains no terms at all.
-    pub fn empty(record_option: IndexRecordOption) -> InvertedIndexReader {
+    pub fn empty(field_type: &FieldType) -> InvertedIndexReader {
+        let record_option = field_type
+            .get_index_record_option()
+            .unwrap_or(IndexRecordOption::Basic);
         InvertedIndexReader {
             termdict: TermDictionary::empty(),
-            postings_file_slice: FileSlice::empty(),
+            postings_source: ReadOnlySource::empty(),
-            positions_file_slice: FileSlice::empty(),
+            positions_source: ReadOnlySource::empty(),
-            positions_idx_file_slice: FileSlice::empty(),
+            positions_idx_source: ReadOnlySource::empty(),
             record_option,
             total_num_tokens: 0u64,
         }
     }
 
     /// Returns the term info associated with the term.
-    pub fn get_term_info(&self, term: &Term) -> io::Result<Option<TermInfo>> {
+    pub fn get_term_info(&self, term: &Term) -> Option<TermInfo> {
         self.termdict.get(term.value_bytes())
     }
 
@@ -89,12 +93,12 @@ impl InvertedIndexReader {
         &self,
         term_info: &TermInfo,
         block_postings: &mut BlockSegmentPostings,
-    ) -> io::Result<()> {
+    ) {
-        let start_offset = term_info.postings_start_offset as usize;
+        let offset = term_info.postings_offset as usize;
-        let stop_offset = term_info.postings_stop_offset as usize;
+        let end_source = self.postings_source.len();
-        let postings_slice = self.postings_file_slice.slice(start_offset, stop_offset);
+        let postings_slice = self.postings_source.slice(offset, end_source);
-        block_postings.reset(term_info.doc_freq, postings_slice.read_bytes()?);
+        let postings_reader = OwnedRead::new(postings_slice);
-        Ok(())
+        block_postings.reset(term_info.doc_freq, postings_reader);
     }
 
     /// Returns a block postings given a `Term`.
@@ -105,10 +109,9 @@ impl InvertedIndexReader {
         &self,
         term: &Term,
         option: IndexRecordOption,
-    ) -> io::Result<Option<BlockSegmentPostings>> {
+    ) -> Option<BlockSegmentPostings> {
-        self.get_term_info(term)?
+        self.get_term_info(term)
             .map(move |term_info| self.read_block_postings_from_terminfo(&term_info, option))
-            .transpose()
     }
 
     /// Returns a block postings given a `term_info`.
@@ -119,14 +122,12 @@ impl InvertedIndexReader {
         &self,
         term_info: &TermInfo,
         requested_option: IndexRecordOption,
-    ) -> io::Result<BlockSegmentPostings> {
+    ) -> BlockSegmentPostings {
-        let postings_data = self.postings_file_slice.slice(
+        let offset = term_info.postings_offset as usize;
-            term_info.postings_start_offset as usize,
+        let postings_data = self.postings_source.slice_from(offset);
-            term_info.postings_stop_offset as usize,
+        BlockSegmentPostings::from_data(
-        );
-        BlockSegmentPostings::open(
             term_info.doc_freq,
-            postings_data,
+            OwnedRead::new(postings_data),
             self.record_option,
             requested_option,
         )
@@ -140,23 +141,20 @@ impl InvertedIndexReader {
         &self,
         term_info: &TermInfo,
         option: IndexRecordOption,
-    ) -> io::Result<SegmentPostings> {
+    ) -> SegmentPostings {
-        let block_postings = self.read_block_postings_from_terminfo(term_info, option)?;
+        let block_postings = self.read_block_postings_from_terminfo(term_info, option);
         let position_stream = {
             if option.has_positions() {
-                let position_reader = self.positions_file_slice.clone();
+                let position_reader = self.positions_source.clone();
-                let skip_reader = self.positions_idx_file_slice.clone();
+                let skip_reader = self.positions_idx_source.clone();
                 let position_reader =
-                    PositionReader::new(position_reader, skip_reader, term_info.positions_idx)?;
+                    PositionReader::new(position_reader, skip_reader, term_info.positions_idx);
                 Some(position_reader)
             } else {
                 None
             }
         };
-        Ok(SegmentPostings::from_block_postings(
+        SegmentPostings::from_block_postings(block_postings, position_stream)
-            block_postings,
-            position_stream,
-        ))
     }
 
     /// Returns the total number of tokens recorded for all documents
@@ -175,31 +173,24 @@ impl InvertedIndexReader {
     /// For instance, requesting `IndexRecordOption::Freq` for a
     /// `TextIndexingOptions` that does not index position will return a `SegmentPostings`
     /// with `DocId`s and frequencies.
-    pub fn read_postings(
+    pub fn read_postings(&self, term: &Term, option: IndexRecordOption) -> Option<SegmentPostings> {
-        &self,
+        self.get_term_info(term)
-        term: &Term,
-        option: IndexRecordOption,
-    ) -> io::Result<Option<SegmentPostings>> {
-        self.get_term_info(term)?
             .map(move |term_info| self.read_postings_from_terminfo(&term_info, option))
-            .transpose()
     }
 
     pub(crate) fn read_postings_no_deletes(
         &self,
         term: &Term,
         option: IndexRecordOption,
-    ) -> io::Result<Option<SegmentPostings>> {
+    ) -> Option<SegmentPostings> {
-        self.get_term_info(term)?
+        self.get_term_info(term)
             .map(|term_info| self.read_postings_from_terminfo(&term_info, option))
-            .transpose()
     }
 
     /// Returns the number of documents containing the term.
-    pub fn doc_freq(&self, term: &Term) -> io::Result<u32> {
+    pub fn doc_freq(&self, term: &Term) -> u32 {
-        Ok(self
+        self.get_term_info(term)
-            .get_term_info(term)?
             .map(|term_info| term_info.doc_freq)
-            .unwrap_or(0u32))
+            .unwrap_or(0u32)
     }
 }

src/core/searcher.rs

@@ -1,17 +1,41 @@
 use crate::collector::Collector;
+use crate::collector::SegmentCollector;
 use crate::core::Executor;
-
+use crate::core::InvertedIndexReader;
 use crate::core::SegmentReader;
 use crate::query::Query;
+use crate::query::Scorer;
+use crate::query::Weight;
 use crate::schema::Document;
 use crate::schema::Schema;
-use crate::schema::Term;
+use crate::schema::{Field, Term};
 use crate::space_usage::SearcherSpaceUsage;
 use crate::store::StoreReader;
+use crate::termdict::TermMerger;
 use crate::DocAddress;
 use crate::Index;
+use std::fmt;
+use std::sync::Arc;
 
-use std::{fmt, io};
+fn collect_segment<C: Collector>(
+    collector: &C,
+    weight: &dyn Weight,
+    segment_ord: u32,
+    segment_reader: &SegmentReader,
+) -> crate::Result<C::Fruit> {
+    let mut scorer = weight.scorer(segment_reader, 1.0f32)?;
+    let mut segment_collector = collector.for_segment(segment_ord as u32, segment_reader)?;
+    if let Some(delete_bitset) = segment_reader.delete_bitset() {
+        scorer.for_each(&mut |doc, score| {
+            if delete_bitset.is_alive(doc) {
+                segment_collector.collect(doc, score);
+            }
+        });
+    } else {
+        scorer.for_each(&mut |doc, score| segment_collector.collect(doc, score));
+    }
+    Ok(segment_collector.harvest())
+}
 
 /// Holds a list of `SegmentReader`s ready for search.
 ///
@@ -31,17 +55,17 @@ impl Searcher {
         schema: Schema,
         index: Index,
         segment_readers: Vec<SegmentReader>,
-    ) -> io::Result<Searcher> {
+    ) -> Searcher {
-        let store_readers: Vec<StoreReader> = segment_readers
+        let store_readers = segment_readers
             .iter()
             .map(SegmentReader::get_store_reader)
-            .collect::<io::Result<Vec<_>>>()?;
+            .collect();
-        Ok(Searcher {
+        Searcher {
             schema,
             index,
             segment_readers,
             store_readers,
-        })
+        }
     }
 
     /// Returns the `Index` associated to the `Searcher`
@@ -74,14 +98,13 @@ impl Searcher {
 
     /// Return the overall number of documents containing
     /// the given term.
-    pub fn doc_freq(&self, term: &Term) -> crate::Result<u64> {
+    pub fn doc_freq(&self, term: &Term) -> u64 {
-        let mut total_doc_freq = 0;
+        self.segment_readers
-        for segment_reader in &self.segment_readers {
+            .iter()
-            let inverted_index = segment_reader.inverted_index(term.field())?;
+            .map(|segment_reader| {
-            let doc_freq = inverted_index.doc_freq(term)?;
+                u64::from(segment_reader.inverted_index(term.field()).doc_freq(term))
-            total_doc_freq += u64::from(doc_freq);
+            })
-        }
+            .sum::<u64>()
-        Ok(total_doc_freq)
     }
 
     /// Return the list of segment readers
@@ -140,20 +163,56 @@ impl Searcher {
         let segment_readers = self.segment_readers();
         let fruits = executor.map(
             |(segment_ord, segment_reader)| {
-                collector.collect_segment(weight.as_ref(), segment_ord as u32, segment_reader)
+                collect_segment(
+                    collector,
+                    weight.as_ref(),
+                    segment_ord as u32,
+                    segment_reader,
+                )
             },
             segment_readers.iter().enumerate(),
         )?;
         collector.merge_fruits(fruits)
     }
 
+    /// Return the field searcher associated to a `Field`.
+    pub fn field(&self, field: Field) -> FieldSearcher {
+        let inv_index_readers = self
+            .segment_readers
+            .iter()
+            .map(|segment_reader| segment_reader.inverted_index(field))
+            .collect::<Vec<_>>();
+        FieldSearcher::new(inv_index_readers)
+    }
+
     /// Summarize total space usage of this searcher.
-    pub fn space_usage(&self) -> io::Result<SearcherSpaceUsage> {
+    pub fn space_usage(&self) -> SearcherSpaceUsage {
         let mut space_usage = SearcherSpaceUsage::new();
-        for segment_reader in &self.segment_readers {
+        for segment_reader in self.segment_readers.iter() {
-            space_usage.add_segment(segment_reader.space_usage()?);
+            space_usage.add_segment(segment_reader.space_usage());
         }
-        Ok(space_usage)
+        space_usage
+    }
+}
+
+pub struct FieldSearcher {
+    inv_index_readers: Vec<Arc<InvertedIndexReader>>,
+}
+
+impl FieldSearcher {
+    fn new(inv_index_readers: Vec<Arc<InvertedIndexReader>>) -> FieldSearcher {
+        FieldSearcher { inv_index_readers }
+    }
+
+    /// Returns a Stream over all of the sorted unique terms of
+    /// for the given field.
+    pub fn terms(&self) -> TermMerger<'_> {
+        let term_streamers: Vec<_> = self
+            .inv_index_readers
+            .iter()
+            .map(|inverted_index| inverted_index.terms().stream())
+            .collect();
+        TermMerger::new(term_streamers)
     }
 }
 

src/core/segment.rs

@@ -3,41 +3,140 @@ use crate::core::Index;
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::directory::error::{OpenReadError, OpenWriteError};
-use crate::directory::Directory;
+use crate::directory::{Directory, ManagedDirectory, RAMDirectory};
-use crate::directory::{FileSlice, WritePtr};
+use crate::directory::{ReadOnlySource, WritePtr};
 use crate::indexer::segment_serializer::SegmentSerializer;
 use crate::schema::Schema;
 use crate::Opstamp;
 use std::fmt;
+use std::ops::{Deref, DerefMut};
 use std::path::PathBuf;
+use crate::indexer::{ResourceManager};
+
+#[derive(Clone)]
+pub(crate) enum SegmentDirectory {
+    Persisted(ManagedDirectory),
+    Volatile {
+        directory: RAMDirectory,
+    },
+}
+
+impl SegmentDirectory {
+    fn new_volatile(memory_manager: ResourceManager) -> SegmentDirectory {
+        SegmentDirectory::Volatile {
+            directory: RAMDirectory::create_with_memory_manager(memory_manager),
+        }
+    }
+}
+
+impl fmt::Debug for SegmentDirectory {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            SegmentDirectory::Volatile { .. } => write!(f, "volatile")?,
+            SegmentDirectory::Persisted(dir) => write!(f, "Persisted({:?})", dir)?,
+        }
+        Ok(())
+    }
+}
+
+impl From<ManagedDirectory> for SegmentDirectory {
+    fn from(directory: ManagedDirectory) -> Self {
+        SegmentDirectory::Persisted(directory)
+    }
+}
+
+impl Deref for SegmentDirectory {
+    type Target = dyn Directory;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            SegmentDirectory::Volatile {
+                directory, ..
+            } => directory,
+            SegmentDirectory::Persisted(dir) => dir,
+        }
+    }
+}
+
+impl DerefMut for SegmentDirectory {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        match self {
+            SegmentDirectory::Volatile { directory, .. } => directory,
+            SegmentDirectory::Persisted(dir) => dir,
+        }
+    }
+}
 
 /// A segment is a piece of the index.
 #[derive(Clone)]
 pub struct Segment {
-    index: Index,
+    schema: Schema,
     meta: SegmentMeta,
+    directory: SegmentDirectory,
 }
 
 impl fmt::Debug for Segment {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "Segment({:?})", self.id().uuid_string())
+        write!(
+            f,
+            "Segment(id={:?}, directory={:?})",
+            self.id().uuid_string(),
+            self.directory
+        )
     }
 }
 
 impl Segment {
-    /// Creates a new segment given an `Index` and a `SegmentId`
+    pub(crate) fn new_persisted(
-    pub(crate) fn for_index(index: Index, meta: SegmentMeta) -> Segment {
+        meta: SegmentMeta,
-        Segment { index, meta }
+        directory: ManagedDirectory,
+        schema: Schema,
+    ) -> Segment {
+        Segment {
+            meta,
+            schema,
+            directory: SegmentDirectory::from(directory),
+        }
     }
 
-    /// Returns the index the segment belongs to.
+    /// Creates a new segment that embeds its own `RAMDirectory`.
-    pub fn index(&self) -> &Index {
+    ///
-        &self.index
+    /// That segment is entirely dissociated from the index directory.
+    /// It will be persisted by a background thread in charge of IO.
+    pub fn new_volatile(meta: SegmentMeta, schema: Schema, resource_manager: ResourceManager) -> Segment {
+        Segment {
+            schema,
+            meta,
+            directory: SegmentDirectory::new_volatile(resource_manager),
+        }
+    }
+
+    /// Creates a new segment given an `Index` and a `SegmentId`
+    pub(crate) fn for_index(index: Index, meta: SegmentMeta) -> Segment {
+        let segment_directory = index.directory().clone();
+        Segment::new_persisted(meta, segment_directory, index.schema())
+    }
+
+    /// Persists a given `Segment` to a directory.
+    pub fn persist(&mut self, mut dest_directory: ManagedDirectory) -> crate::Result<()> {
+        if let SegmentDirectory::Persisted(_) = self.directory {
+            // this segment is already persisted.
+            return Ok(());
+        }
+        if let SegmentDirectory::Volatile { directory, ..} = &self.directory {
+            directory.persist(&mut dest_directory)?;
+        }
+        self.directory = SegmentDirectory::Persisted(dest_directory);
+        Ok(())
+    }
+
+    pub fn into_volatile(&self, memory_manager: ResourceManager) -> Segment {
+        Segment::new_volatile(self.meta.clone(), self.schema.clone(), memory_manager)
     }
 
     /// Returns our index's schema.
     pub fn schema(&self) -> Schema {
-        self.index.schema()
+        self.schema.clone()
     }
 
     /// Returns the segment meta-information
@@ -51,16 +150,18 @@ impl Segment {
     /// as we finalize a fresh new segment.
     pub(crate) fn with_max_doc(self, max_doc: u32) -> Segment {
         Segment {
-            index: self.index,
+            schema: self.schema,
             meta: self.meta.with_max_doc(max_doc),
+            directory: self.directory,
         }
     }
 
     #[doc(hidden)]
     pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: Opstamp) -> Segment {
         Segment {
-            index: self.index,
+            schema: self.schema,
             meta: self.meta.with_delete_meta(num_deleted_docs, opstamp),
+            directory: self.directory,
         }
     }
 
@@ -78,16 +179,17 @@ impl Segment {
     }
 
     /// Open one of the component file for a *regular* read.
-    pub fn open_read(&self, component: SegmentComponent) -> Result<FileSlice, OpenReadError> {
+    pub fn open_read(&self, component: SegmentComponent) -> Result<ReadOnlySource, OpenReadError> {
         let path = self.relative_path(component);
-        self.index.directory().open_read(&path)
+        let source = self.directory.open_read(&path)?;
+        Ok(source)
     }
 
     /// Open one of the component file for *regular* write.
     pub fn open_write(&mut self, component: SegmentComponent) -> Result<WritePtr, OpenWriteError> {
         let path = self.relative_path(component);
-        let write = self.index.directory_mut().open_write(&path)?;
+        let wrt = self.directory.open_write(&path)?;
-        Ok(write)
+        Ok(wrt)
     }
 }
 

src/core/segment_component.rs

@@ -20,7 +20,7 @@ pub enum SegmentComponent {
     /// Dictionary associating `Term`s to `TermInfo`s which is
     /// simply an address into the `postings` file and the `positions` file.
     TERMS,
-    /// Row-oriented, compressed storage of the documents.
+    /// Row-oriented, LZ4-compressed storage of the documents.
     /// Accessing a document from the store is relatively slow, as it
     /// requires to decompress the entire block it belongs to.
     STORE,

src/core/segment_reader.rs

@@ -1,26 +1,26 @@
+use crate::common::CompositeFile;
 use crate::common::HasLen;
 use crate::core::InvertedIndexReader;
 use crate::core::Segment;
 use crate::core::SegmentComponent;
 use crate::core::SegmentId;
-use crate::directory::FileSlice;
+use crate::directory::ReadOnlySource;
 use crate::fastfield::DeleteBitSet;
 use crate::fastfield::FacetReader;
 use crate::fastfield::FastFieldReaders;
-use crate::fieldnorm::{FieldNormReader, FieldNormReaders};
+use crate::fieldnorm::FieldNormReader;
+use crate::schema::Field;
 use crate::schema::FieldType;
 use crate::schema::Schema;
-use crate::schema::{Field, IndexRecordOption};
 use crate::space_usage::SegmentSpaceUsage;
 use crate::store::StoreReader;
 use crate::termdict::TermDictionary;
 use crate::DocId;
-use crate::{common::CompositeFile, error::DataCorruption};
 use fail::fail_point;
+use std::collections::HashMap;
 use std::fmt;
 use std::sync::Arc;
 use std::sync::RwLock;
-use std::{collections::HashMap, io};
 
 /// Entry point to access all of the datastructures of the `Segment`
 ///
@@ -48,9 +48,9 @@ pub struct SegmentReader {
     positions_composite: CompositeFile,
     positions_idx_composite: CompositeFile,
     fast_fields_readers: Arc<FastFieldReaders>,
-    fieldnorm_readers: FieldNormReaders,
+    fieldnorms_composite: CompositeFile,
 
-    store_file: FileSlice,
+    store_source: ReadOnlySource,
     delete_bitset_opt: Option<DeleteBitSet>,
     schema: Schema,
 }
@@ -106,26 +106,16 @@ impl SegmentReader {
     }
 
     /// Accessor to the `FacetReader` associated to a given `Field`.
-    pub fn facet_reader(&self, field: Field) -> crate::Result<FacetReader> {
+    pub fn facet_reader(&self, field: Field) -> Option<FacetReader> {
         let field_entry = self.schema.get_field_entry(field);
         if field_entry.field_type() != &FieldType::HierarchicalFacet {
-            return Err(crate::TantivyError::InvalidArgument(format!(
+            return None;
-                "Field {:?} is not a facet field.",
-                field_entry.name()
-            )));
         }
-        let term_ords_reader = self.fast_fields().u64s(field).ok_or_else(|| {
+        let term_ords_reader = self.fast_fields().u64s(field)?;
-            DataCorruption::comment_only(format!(
+        let termdict_source = self.termdict_composite.open_read(field)?;
-                "Cannot find data for hierarchical facet {:?}",
+        let termdict = TermDictionary::from_source(&termdict_source);
-                field_entry.name()
+        let facet_reader = FacetReader::new(term_ords_reader, termdict);
-            ))
+        Some(facet_reader)
-        })?;
-        let termdict = self
-            .termdict_composite
-            .open_read(field)
-            .map(TermDictionary::open)
-            .unwrap_or_else(|| Ok(TermDictionary::empty()))?;
-        Ok(FacetReader::new(term_ords_reader, termdict))
     }
 
     /// Accessor to the segment's `Field norms`'s reader.
@@ -135,45 +125,47 @@ impl SegmentReader {
     ///
     /// They are simply stored as a fast field, serialized in
     /// the `.fieldnorm` file of the segment.
-    pub fn get_fieldnorms_reader(&self, field: Field) -> crate::Result<FieldNormReader> {
+    pub fn get_fieldnorms_reader(&self, field: Field) -> FieldNormReader {
-        self.fieldnorm_readers.get_field(field)?.ok_or_else(|| {
+        if let Some(fieldnorm_source) = self.fieldnorms_composite.open_read(field) {
+            FieldNormReader::open(fieldnorm_source)
+        } else {
             let field_name = self.schema.get_field_name(field);
             let err_msg = format!(
-                "Field norm not found for field {:?}. Was it marked as indexed during indexing?",
+                "Field norm not found for field {:?}. Was it market as indexed during indexing.",
                 field_name
             );
-            crate::TantivyError::SchemaError(err_msg)
+            panic!(err_msg);
-        })
+        }
     }
 
     /// Accessor to the segment's `StoreReader`.
-    pub fn get_store_reader(&self) -> io::Result<StoreReader> {
+    pub fn get_store_reader(&self) -> StoreReader {
-        StoreReader::open(self.store_file.clone())
+        StoreReader::from_source(self.store_source.clone())
     }
 
     /// Open a new segment for reading.
     pub fn open(segment: &Segment) -> crate::Result<SegmentReader> {
-        let termdict_file = segment.open_read(SegmentComponent::TERMS)?;
+        let termdict_source = segment.open_read(SegmentComponent::TERMS)?;
-        let termdict_composite = CompositeFile::open(&termdict_file)?;
+        let termdict_composite = CompositeFile::open(&termdict_source)?;
 
-        let store_file = segment.open_read(SegmentComponent::STORE)?;
+        let store_source = segment.open_read(SegmentComponent::STORE)?;
 
         fail_point!("SegmentReader::open#middle");
 
-        let postings_file = segment.open_read(SegmentComponent::POSTINGS)?;
+        let postings_source = segment.open_read(SegmentComponent::POSTINGS)?;
-        let postings_composite = CompositeFile::open(&postings_file)?;
+        let postings_composite = CompositeFile::open(&postings_source)?;
 
         let positions_composite = {
-            if let Ok(positions_file) = segment.open_read(SegmentComponent::POSITIONS) {
+            if let Ok(source) = segment.open_read(SegmentComponent::POSITIONS) {
-                CompositeFile::open(&positions_file)?
+                CompositeFile::open(&source)?
             } else {
                 CompositeFile::empty()
             }
         };
 
         let positions_idx_composite = {
-            if let Ok(positions_skip_file) = segment.open_read(SegmentComponent::POSITIONSSKIP) {
+            if let Ok(source) = segment.open_read(SegmentComponent::POSITIONSSKIP) {
-                CompositeFile::open(&positions_skip_file)?
+                CompositeFile::open(&source)?
             } else {
                 CompositeFile::empty()
             }
@@ -186,27 +178,26 @@ impl SegmentReader {
         let fast_field_readers =
             Arc::new(FastFieldReaders::load_all(&schema, &fast_fields_composite)?);
 
-        let fieldnorm_data = segment.open_read(SegmentComponent::FIELDNORMS)?;
+        let fieldnorms_data = segment.open_read(SegmentComponent::FIELDNORMS)?;
-        let fieldnorm_readers = FieldNormReaders::open(fieldnorm_data)?;
+        let fieldnorms_composite = CompositeFile::open(&fieldnorms_data)?;
 
         let delete_bitset_opt = if segment.meta().has_deletes() {
             let delete_data = segment.open_read(SegmentComponent::DELETE)?;
-            let delete_bitset = DeleteBitSet::open(delete_data)?;
+            Some(DeleteBitSet::open(delete_data))
-            Some(delete_bitset)
         } else {
             None
         };
 
         Ok(SegmentReader {
-            inv_idx_reader_cache: Default::default(),
+            inv_idx_reader_cache: Arc::new(RwLock::new(HashMap::new())),
             max_doc: segment.meta().max_doc(),
             num_docs: segment.meta().num_docs(),
             termdict_composite,
             postings_composite,
             fast_fields_readers: fast_field_readers,
-            fieldnorm_readers,
+            fieldnorms_composite,
             segment_id: segment.id(),
-            store_file,
+            store_source,
             delete_bitset_opt,
             positions_composite,
             positions_idx_composite,
@@ -221,64 +212,58 @@ impl SegmentReader {
     /// The field reader is in charge of iterating through the
     /// term dictionary associated to a specific field,
     /// and opening the posting list associated to any term.
-    ///
+    pub fn inverted_index(&self, field: Field) -> Arc<InvertedIndexReader> {
-    /// If the field is marked as index, a warn is logged and an empty `InvertedIndexReader`
-    /// is returned.
-    /// Similarly if the field is marked as indexed but no term has been indexed for the given
-    /// index. an empty `InvertedIndexReader` is returned (but no warning is logged).
-    pub fn inverted_index(&self, field: Field) -> crate::Result<Arc<InvertedIndexReader>> {
         if let Some(inv_idx_reader) = self
             .inv_idx_reader_cache
             .read()
             .expect("Lock poisoned. This should never happen")
             .get(&field)
         {
-            return Ok(Arc::clone(inv_idx_reader));
+            return Arc::clone(inv_idx_reader);
         }
         let field_entry = self.schema.get_field_entry(field);
         let field_type = field_entry.field_type();
         let record_option_opt = field_type.get_index_record_option();
 
         if record_option_opt.is_none() {
-            warn!("Field {:?} does not seem indexed.", field_entry.name());
+            panic!("Field {:?} does not seem indexed.", field_entry.name());
         }
 
-        let postings_file_opt = self.postings_composite.open_read(field);
+        let record_option = record_option_opt.unwrap();
 
-        if postings_file_opt.is_none() || record_option_opt.is_none() {
+        let postings_source_opt = self.postings_composite.open_read(field);
+
+        if postings_source_opt.is_none() {
             // no documents in the segment contained this field.
             // As a result, no data is associated to the inverted index.
             //
             // Returns an empty inverted index.
-            let record_option = record_option_opt.unwrap_or(IndexRecordOption::Basic);
+            return Arc::new(InvertedIndexReader::empty(field_type));
-            return Ok(Arc::new(InvertedIndexReader::empty(record_option)));
         }
 
-        let record_option = record_option_opt.unwrap();
+        let postings_source = postings_source_opt.unwrap();
-        let postings_file = postings_file_opt.unwrap();
 
-        let termdict_file: FileSlice = self.termdict_composite.open_read(field)
+        let termdict_source = self.termdict_composite.open_read(field).expect(
-            .ok_or_else(||
+            "Failed to open field term dictionary in composite file. Is the field indexed?",
-               DataCorruption::comment_only(format!("Failed to open field {:?}'s term dictionary in the composite file. Has the schema been modified?", field_entry.name()))
+        );
-            )?;
 
-        let positions_file = self
+        let positions_source = self
             .positions_composite
             .open_read(field)
             .expect("Index corrupted. Failed to open field positions in composite file.");
 
-        let positions_idx_file = self
+        let positions_idx_source = self
             .positions_idx_composite
             .open_read(field)
             .expect("Index corrupted. Failed to open field positions in composite file.");
 
         let inv_idx_reader = Arc::new(InvertedIndexReader::new(
-            TermDictionary::open(termdict_file)?,
+            TermDictionary::from_source(&termdict_source),
-            postings_file,
+            postings_source,
-            positions_file,
+            positions_source,
-            positions_idx_file,
+            positions_idx_source,
             record_option,
-        )?);
+        ));
 
         // by releasing the lock in between, we may end up opening the inverting index
         // twice, but this is fine.
@@ -287,7 +272,7 @@ impl SegmentReader {
             .expect("Field reader cache lock poisoned. This should never happen.")
             .insert(field, Arc::clone(&inv_idx_reader));
 
-        Ok(inv_idx_reader)
+        inv_idx_reader
     }
 
     /// Returns the segment id
@@ -310,26 +295,26 @@ impl SegmentReader {
     }
 
     /// Returns an iterator that will iterate over the alive document ids
-    pub fn doc_ids_alive<'a>(&'a self) -> impl Iterator<Item = DocId> + 'a {
+    pub fn doc_ids_alive(&self) -> SegmentReaderAliveDocsIterator<'_> {
-        (0u32..self.max_doc).filter(move |doc| !self.is_deleted(*doc))
+        SegmentReaderAliveDocsIterator::new(&self)
     }
 
     /// Summarize total space usage of this segment.
-    pub fn space_usage(&self) -> io::Result<SegmentSpaceUsage> {
+    pub fn space_usage(&self) -> SegmentSpaceUsage {
-        Ok(SegmentSpaceUsage::new(
+        SegmentSpaceUsage::new(
             self.num_docs(),
             self.termdict_composite.space_usage(),
             self.postings_composite.space_usage(),
             self.positions_composite.space_usage(),
             self.positions_idx_composite.space_usage(),
             self.fast_fields_readers.space_usage(),
-            self.fieldnorm_readers.space_usage(),
+            self.fieldnorms_composite.space_usage(),
-            self.get_store_reader()?.space_usage(),
+            self.get_store_reader().space_usage(),
             self.delete_bitset_opt
                 .as_ref()
                 .map(DeleteBitSet::space_usage)
                 .unwrap_or(0),
-        ))
+        )
     }
 }
 
@@ -339,6 +324,52 @@ impl fmt::Debug for SegmentReader {
     }
 }
 
+/// Implements the iterator trait to allow easy iteration
+/// over non-deleted ("alive") DocIds in a SegmentReader
+pub struct SegmentReaderAliveDocsIterator<'a> {
+    reader: &'a SegmentReader,
+    max_doc: DocId,
+    current: DocId,
+}
+
+impl<'a> SegmentReaderAliveDocsIterator<'a> {
+    pub fn new(reader: &'a SegmentReader) -> SegmentReaderAliveDocsIterator<'a> {
+        SegmentReaderAliveDocsIterator {
+            reader,
+            max_doc: reader.max_doc(),
+            current: 0,
+        }
+    }
+}
+
+impl<'a> Iterator for SegmentReaderAliveDocsIterator<'a> {
+    type Item = DocId;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // TODO: Use TinySet (like in BitSetDocSet) to speed this process up
+        if self.current >= self.max_doc {
+            return None;
+        }
+
+        // find the next alive doc id
+        while self.reader.is_deleted(self.current) {
+            self.current += 1;
+
+            if self.current >= self.max_doc {
+                return None;
+            }
+        }
+
+        // capture the current alive DocId
+        let result = Some(self.current);
+
+        // move down the chain
+        self.current += 1;
+
+        result
+    }
+}
+
 #[cfg(test)]
 mod test {
     use crate::core::Index;
@@ -346,7 +377,7 @@ mod test {
     use crate::DocId;
 
     #[test]
-    fn test_alive_docs_iterator() -> crate::Result<()> {
+    fn test_alive_docs_iterator() {
         let mut schema_builder = Schema::builder();
         schema_builder.add_text_field("name", TEXT | STORED);
         let schema = schema_builder.build();
@@ -354,26 +385,26 @@ mod test {
         let name = schema.get_field("name").unwrap();
 
         {
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.add_document(doc!(name => "tantivy"));
             index_writer.add_document(doc!(name => "horse"));
             index_writer.add_document(doc!(name => "jockey"));
             index_writer.add_document(doc!(name => "cap"));
+
             // we should now have one segment with two docs
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
         }
 
         {
-            let mut index_writer2 = index.writer(50_000_000)?;
+            let mut index_writer2 = index.writer(50_000_000).unwrap();
             index_writer2.delete_term(Term::from_field_text(name, "horse"));
             index_writer2.delete_term(Term::from_field_text(name, "cap"));
 
             // ok, now we should have a deleted doc
-            index_writer2.commit()?;
+            index_writer2.commit().unwrap();
         }
-        let searcher = index.reader()?.searcher();
+        let searcher = index.reader().unwrap().searcher();
         let docs: Vec<DocId> = searcher.segment_reader(0).doc_ids_alive().collect();
         assert_eq!(vec![0u32, 2u32], docs);
-        Ok(())
     }
 }

src/directory/directory.rs

@@ -1,9 +1,9 @@
 use crate::directory::directory_lock::Lock;
 use crate::directory::error::LockError;
 use crate::directory::error::{DeleteError, OpenReadError, OpenWriteError};
+use crate::directory::WatchCallback;
 use crate::directory::WatchHandle;
-use crate::directory::{FileHandle, WatchCallback};
+use crate::directory::{ReadOnlySource, WritePtr};
-use crate::directory::{FileSlice, WritePtr};
 use std::fmt;
 use std::io;
 use std::io::Write;
@@ -11,6 +11,7 @@ use std::marker::Send;
 use std::marker::Sync;
 use std::path::Path;
 use std::path::PathBuf;
+use std::result;
 use std::thread;
 use std::time::Duration;
 
@@ -79,7 +80,7 @@ fn try_acquire_lock(
 ) -> Result<DirectoryLock, TryAcquireLockError> {
     let mut write = directory.open_write(filepath).map_err(|e| match e {
         OpenWriteError::FileAlreadyExists(_) => TryAcquireLockError::FileExists,
-        OpenWriteError::IOError { io_error, .. } => TryAcquireLockError::IOError(io_error),
+        OpenWriteError::IOError(io_error) => TryAcquireLockError::IOError(io_error.into()),
     })?;
     write.flush().map_err(TryAcquireLockError::IOError)?;
     Ok(DirectoryLock::from(Box::new(DirectoryLockGuard {
@@ -108,43 +109,37 @@ fn retry_policy(is_blocking: bool) -> RetryPolicy {
 /// should be your default choice.
 /// - The [`RAMDirectory`](struct.RAMDirectory.html), which
 /// should be used mostly for tests.
+///
 pub trait Directory: DirectoryClone + fmt::Debug + Send + Sync + 'static {
-    /// Opens a file and returns a boxed `FileHandle`.
+    /// Opens a virtual file for read.
     ///
-    /// Users of `Directory` should typically call `Directory::open_read(...)`,
-    /// while `Directory` implementor should implement `get_file_handle()`.
-    fn get_file_handle(&self, path: &Path) -> Result<Box<dyn FileHandle>, OpenReadError>;
-
     /// Once a virtual file is open, its data may not
     /// change.
     ///
     /// Specifically, subsequent writes or flushes should
-    /// have no effect on the returned `FileSlice` object.
+    /// have no effect on the returned `ReadOnlySource` object.
     ///
     /// You should only use this to read files create with [Directory::open_write].
-    fn open_read(&self, path: &Path) -> Result<FileSlice, OpenReadError> {
+    fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError>;
-        let file_handle = self.get_file_handle(path)?;
-        Ok(FileSlice::new(file_handle))
-    }
 
     /// Removes a file
     ///
     /// Removing a file will not affect an eventual
-    /// existing FileSlice pointing to it.
+    /// existing ReadOnlySource pointing to it.
     ///
     /// Removing a nonexistent file, yields a
     /// `DeleteError::DoesNotExist`.
-    fn delete(&self, path: &Path) -> Result<(), DeleteError>;
+    fn delete(&self, path: &Path) -> result::Result<(), DeleteError>;
 
     /// Returns true iff the file exists
-    fn exists(&self, path: &Path) -> Result<bool, OpenReadError>;
+    fn exists(&self, path: &Path) -> bool;
 
     /// Opens a writer for the *virtual file* associated with
     /// a Path.
     ///
     /// Right after this call, the file should be created
     /// and any subsequent call to `open_read` for the
-    /// same path should return a `FileSlice`.
+    /// same path should return a `ReadOnlySource`.
     ///
     /// Write operations may be aggressively buffered.
     /// The client of this trait is responsible for calling flush
@@ -158,7 +153,7 @@ pub trait Directory: DirectoryClone + fmt::Debug + Send + Sync + 'static {
     /// was not called.
     ///
     /// The file may not previously exist.
-    fn open_write(&self, path: &Path) -> Result<WritePtr, OpenWriteError>;
+    fn open_write(&mut self, path: &Path) -> Result<WritePtr, OpenWriteError>;
 
     /// Reads the full content file that has been written using
     /// atomic_write.
@@ -174,7 +169,7 @@ pub trait Directory: DirectoryClone + fmt::Debug + Send + Sync + 'static {
     /// a partially written file.
     ///
     /// The file may or may not previously exist.
-    fn atomic_write(&self, path: &Path, data: &[u8]) -> io::Result<()>;
+    fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()>;
 
     /// Acquire a lock in the given directory.
     ///

src/directory/error.rs

@@ -1,68 +1,162 @@
 use crate::Version;
+use std::error::Error as StdError;
 use std::fmt;
 use std::io;
 use std::path::PathBuf;
 
 /// Error while trying to acquire a directory lock.
-#[derive(Debug, Error)]
+#[derive(Debug, Fail)]
 pub enum LockError {
     /// Failed to acquired a lock as it is already held by another
     /// client.
     /// - In the context of a blocking lock, this means the lock was not released within some `timeout` period.
     /// - In the context of a non-blocking lock, this means the lock was busy at the moment of the call.
-    #[error("Could not acquire lock as it is already held, possibly by a different process.")]
+    #[fail(
+        display = "Could not acquire lock as it is already held, possibly by a different process."
+    )]
     LockBusy,
     /// Trying to acquire a lock failed with an `IOError`
-    #[error("Failed to acquire the lock due to an io:Error.")]
+    #[fail(display = "Failed to acquire the lock due to an io:Error.")]
     IOError(io::Error),
 }
 
+/// General IO error with an optional path to the offending file.
+#[derive(Debug)]
+pub struct IOError {
+    path: Option<PathBuf>,
+    err: io::Error,
+}
+
+impl Into<io::Error> for IOError {
+    fn into(self) -> io::Error {
+        self.err
+    }
+}
+
+impl fmt::Display for IOError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.path {
+            Some(ref path) => write!(f, "io error occurred on path '{:?}': '{}'", path, self.err),
+            None => write!(f, "io error occurred: '{}'", self.err),
+        }
+    }
+}
+
+impl StdError for IOError {
+    fn description(&self) -> &str {
+        "io error occurred"
+    }
+
+    fn cause(&self) -> Option<&dyn StdError> {
+        Some(&self.err)
+    }
+}
+
+impl IOError {
+    pub(crate) fn with_path(path: PathBuf, err: io::Error) -> Self {
+        IOError {
+            path: Some(path),
+            err,
+        }
+    }
+}
+
+impl From<io::Error> for IOError {
+    fn from(err: io::Error) -> IOError {
+        IOError { path: None, err }
+    }
+}
+
 /// Error that may occur when opening a directory
-#[derive(Debug, Error)]
+#[derive(Debug)]
 pub enum OpenDirectoryError {
     /// The underlying directory does not exists.
-    #[error("Directory does not exist: '{0}'.")]
     DoesNotExist(PathBuf),
     /// The path exists but is not a directory.
-    #[error("Path exists but is not a directory: '{0}'.")]
     NotADirectory(PathBuf),
-    /// Failed to create a temp directory.
-    #[error("Failed to create a temporary directory: '{0}'.")]
-    FailedToCreateTempDir(io::Error),
     /// IoError
-    #[error("IOError '{io_error:?}' while create directory in: '{directory_path:?}'.")]
+    IoError(io::Error),
-    IoError {
+}
-        /// underlying io Error.
+
-        io_error: io::Error,
+impl From<io::Error> for OpenDirectoryError {
-        /// directory we tried to open.
+    fn from(io_err: io::Error) -> Self {
-        directory_path: PathBuf,
+        OpenDirectoryError::IoError(io_err)
-    },
+    }
+}
+
+impl fmt::Display for OpenDirectoryError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            OpenDirectoryError::DoesNotExist(ref path) => {
+                write!(f, "the underlying directory '{:?}' does not exist", path)
+            }
+            OpenDirectoryError::NotADirectory(ref path) => {
+                write!(f, "the path '{:?}' exists but is not a directory", path)
+            }
+            OpenDirectoryError::IoError(ref err) => write!(
+                f,
+                "IOError while trying to open/create the directory. {:?}",
+                err
+            ),
+        }
+    }
+}
+
+impl StdError for OpenDirectoryError {
+    fn description(&self) -> &str {
+        "error occurred while opening a directory"
+    }
+
+    fn cause(&self) -> Option<&dyn StdError> {
+        None
+    }
 }
 
 /// Error that may occur when starting to write in a file
-#[derive(Debug, Error)]
+#[derive(Debug)]
 pub enum OpenWriteError {
     /// Our directory is WORM, writing an existing file is forbidden.
     /// Checkout the `Directory` documentation.
-    #[error("File already exists: '{0}'")]
     FileAlreadyExists(PathBuf),
     /// Any kind of IO error that happens when
     /// writing in the underlying IO device.
-    #[error("IOError '{io_error:?}' while opening file for write: '{filepath}'.")]
+    IOError(IOError),
-    IOError {
-        /// The underlying `io::Error`.
-        io_error: io::Error,
-        /// File path of the file that tantivy failed to open for write.
-        filepath: PathBuf,
-    },
 }
 
-impl OpenWriteError {
+impl From<IOError> for OpenWriteError {
-    /// Wraps an io error.
+    fn from(err: IOError) -> OpenWriteError {
-    pub fn wrap_io_error(io_error: io::Error, filepath: PathBuf) -> Self {
+        OpenWriteError::IOError(err)
-        Self::IOError { io_error, filepath }
     }
 }
+
+impl fmt::Display for OpenWriteError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            OpenWriteError::FileAlreadyExists(ref path) => {
+                write!(f, "the file '{:?}' already exists", path)
+            }
+            OpenWriteError::IOError(ref err) => write!(
+                f,
+                "an io error occurred while opening a file for writing: '{}'",
+                err
+            ),
+        }
+    }
+}
+
+impl StdError for OpenWriteError {
+    fn description(&self) -> &str {
+        "error occurred while opening a file for writing"
+    }
+
+    fn cause(&self) -> Option<&dyn StdError> {
+        match *self {
+            OpenWriteError::FileAlreadyExists(_) => None,
+            OpenWriteError::IOError(ref err) => Some(err),
+        }
+    }
+}
+
 /// Type of index incompatibility between the library and the index found on disk
 /// Used to catch and provide a hint to solve this incompatibility issue
 pub enum Incompatibility {
@@ -123,47 +217,55 @@ impl fmt::Debug for Incompatibility {
 }
 
 /// Error that may occur when accessing a file read
-#[derive(Debug, Error)]
+#[derive(Debug)]
 pub enum OpenReadError {
     /// The file does not exists.
-    #[error("Files does not exists: {0:?}")]
-    FileDoesNotExist(PathBuf),
-    /// Any kind of io::Error.
-    #[error(
-        "IOError: '{io_error:?}' happened while opening the following file for Read: {filepath}."
-    )]
-    IOError {
-        /// The underlying `io::Error`.
-        io_error: io::Error,
-        /// File path of the file that tantivy failed to open for read.
-        filepath: PathBuf,
-    },
-    /// This library does not support the index version found in file footer.
-    #[error("Index version unsupported: {0:?}")]
-    IncompatibleIndex(Incompatibility),
-}
-
-impl OpenReadError {
-    /// Wraps an io error.
-    pub fn wrap_io_error(io_error: io::Error, filepath: PathBuf) -> Self {
-        Self::IOError { io_error, filepath }
-    }
-}
-/// Error that may occur when trying to delete a file
-#[derive(Debug, Error)]
-pub enum DeleteError {
-    /// The file does not exists.
-    #[error("File does not exists: '{0}'.")]
     FileDoesNotExist(PathBuf),
     /// Any kind of IO error that happens when
     /// interacting with the underlying IO device.
-    #[error("The following IO error happened while deleting file '{filepath}': '{io_error:?}'.")]
+    IOError(IOError),
-    IOError {
+    /// This library doesn't support the index version found on disk
-        /// The underlying `io::Error`.
+    IncompatibleIndex(Incompatibility),
-        io_error: io::Error,
+}
-        /// File path of the file that tantivy failed to delete.
+
-        filepath: PathBuf,
+impl From<IOError> for OpenReadError {
-    },
+    fn from(err: IOError) -> OpenReadError {
+        OpenReadError::IOError(err)
+    }
+}
+
+impl fmt::Display for OpenReadError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            OpenReadError::FileDoesNotExist(ref path) => {
+                write!(f, "the file '{:?}' does not exist", path)
+            }
+            OpenReadError::IOError(ref err) => write!(
+                f,
+                "an io error occurred while opening a file for reading: '{}'",
+                err
+            ),
+            OpenReadError::IncompatibleIndex(ref footer) => {
+                write!(f, "Incompatible index format: {:?}", footer)
+            }
+        }
+    }
+}
+
+/// Error that may occur when trying to delete a file
+#[derive(Debug)]
+pub enum DeleteError {
+    /// The file does not exists.
+    FileDoesNotExist(PathBuf),
+    /// Any kind of IO error that happens when
+    /// interacting with the underlying IO device.
+    IOError(IOError),
+}
+
+impl From<IOError> for DeleteError {
+    fn from(err: IOError) -> DeleteError {
+        DeleteError::IOError(err)
+    }
 }
 
 impl From<Incompatibility> for OpenReadError {
@@ -171,3 +273,29 @@ impl From<Incompatibility> for OpenReadError {
         OpenReadError::IncompatibleIndex(incompatibility)
     }
 }
+
+impl fmt::Display for DeleteError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            DeleteError::FileDoesNotExist(ref path) => {
+                write!(f, "the file '{:?}' does not exist", path)
+            }
+            DeleteError::IOError(ref err) => {
+                write!(f, "an io error occurred while deleting a file: '{}'", err)
+            }
+        }
+    }
+}
+
+impl StdError for DeleteError {
+    fn description(&self) -> &str {
+        "error occurred while deleting a file"
+    }
+
+    fn cause(&self) -> Option<&dyn StdError> {
+        match *self {
+            DeleteError::FileDoesNotExist(_) => None,
+            DeleteError::IOError(ref err) => Some(err),
+        }
+    }
+}

src/directory/file_slice.rs

@@ -1,247 +0,0 @@
-use stable_deref_trait::StableDeref;
-
-use crate::common::HasLen;
-use crate::directory::OwnedBytes;
-use std::sync::{Arc, Weak};
-use std::{io, ops::Deref};
-
-pub type ArcBytes = Arc<dyn Deref<Target = [u8]> + Send + Sync + 'static>;
-pub type WeakArcBytes = Weak<dyn Deref<Target = [u8]> + Send + Sync + 'static>;
-
-/// Objects that represents files sections in tantivy.
-///
-/// By contract, whatever happens to the directory file, as long as a FileHandle
-/// is alive, the data associated with it cannot be altered or destroyed.
-///
-/// The underlying behavior is therefore specific to the `Directory` that created it.
-/// Despite its name, a `FileSlice` may or may not directly map to an actual file
-/// on the filesystem.
-pub trait FileHandle: 'static + Send + Sync + HasLen {
-    /// Reads a slice of bytes.
-    ///
-    /// This method may panic if the range requested is invalid.
-    fn read_bytes(&self, from: usize, to: usize) -> io::Result<OwnedBytes>;
-}
-
-impl FileHandle for &'static [u8] {
-    fn read_bytes(&self, from: usize, to: usize) -> io::Result<OwnedBytes> {
-        let bytes = &self[from..to];
-        Ok(OwnedBytes::new(bytes))
-    }
-}
-
-impl<T: Deref<Target = [u8]>> HasLen for T {
-    fn len(&self) -> usize {
-        self.as_ref().len()
-    }
-}
-
-impl<B> From<B> for FileSlice
-where
-    B: StableDeref + Deref<Target = [u8]> + 'static + Send + Sync,
-{
-    fn from(bytes: B) -> FileSlice {
-        FileSlice::new(Box::new(OwnedBytes::new(bytes)))
-    }
-}
-
-/// Logical slice of read only file in tantivy.
-//
-/// It can be cloned and sliced cheaply.
-///
-#[derive(Clone)]
-pub struct FileSlice {
-    data: Arc<dyn FileHandle>,
-    start: usize,
-    stop: usize,
-}
-
-impl FileSlice {
-    /// Wraps a FileHandle.
-    pub fn new(file_handle: Box<dyn FileHandle>) -> Self {
-        let num_bytes = file_handle.len();
-        FileSlice::new_with_num_bytes(file_handle, num_bytes)
-    }
-
-    /// Wraps a FileHandle.
-    #[doc(hidden)]
-    pub fn new_with_num_bytes(file_handle: Box<dyn FileHandle>, num_bytes: usize) -> Self {
-        FileSlice {
-            data: Arc::from(file_handle),
-            start: 0,
-            stop: num_bytes,
-        }
-    }
-
-    /// Creates a fileslice that is just a view over a slice of the data.
-    ///
-    /// # Panics
-    ///
-    /// Panics if `to < from` or if `to` exceeds the filesize.
-    pub fn slice(&self, from: usize, to: usize) -> FileSlice {
-        assert!(to <= self.len());
-        assert!(to >= from);
-        FileSlice {
-            data: self.data.clone(),
-            start: self.start + from,
-            stop: self.start + to,
-        }
-    }
-
-    /// Creates an empty FileSlice
-    pub fn empty() -> FileSlice {
-        const EMPTY_SLICE: &[u8] = &[];
-        FileSlice::from(EMPTY_SLICE)
-    }
-
-    /// Returns a `OwnedBytes` with all of the data in the `FileSlice`.
-    ///
-    /// The behavior is strongly dependant on the implementation of the underlying
-    /// `Directory` and the `FileSliceTrait` it creates.
-    /// In particular, it is  up to the `Directory` implementation
-    /// to handle caching if needed.
-    pub fn read_bytes(&self) -> io::Result<OwnedBytes> {
-        self.data.read_bytes(self.start, self.stop)
-    }
-
-    /// Reads a specific slice of data.
-    ///
-    /// This is equivalent to running `file_slice.slice(from, to).read_bytes()`.
-    pub fn read_bytes_slice(&self, from: usize, to: usize) -> io::Result<OwnedBytes> {
-        assert!(from <= to);
-        assert!(
-            self.start + to <= self.stop,
-            "`to` exceeds the fileslice length"
-        );
-        self.data.read_bytes(self.start + from, self.start + to)
-    }
-
-    /// Splits the FileSlice at the given offset and return two file slices.
-    /// `file_slice[..split_offset]` and `file_slice[split_offset..]`.
-    ///
-    /// This operation is cheap and must not copy any underlying data.
-    pub fn split(self, left_len: usize) -> (FileSlice, FileSlice) {
-        let left = self.slice_to(left_len);
-        let right = self.slice_from(left_len);
-        (left, right)
-    }
-
-    /// Splits the file slice at the given offset and return two file slices.
-    /// `file_slice[..split_offset]` and `file_slice[split_offset..]`.
-    pub fn split_from_end(self, right_len: usize) -> (FileSlice, FileSlice) {
-        let left_len = self.len() - right_len;
-        self.split(left_len)
-    }
-
-    /// Like `.slice(...)` but enforcing only the `from`
-    /// boundary.
-    ///
-    /// Equivalent to `.slice(from_offset, self.len())`
-    pub fn slice_from(&self, from_offset: usize) -> FileSlice {
-        self.slice(from_offset, self.len())
-    }
-
-    /// Like `.slice(...)` but enforcing only the `to`
-    /// boundary.
-    ///
-    /// Equivalent to `.slice(0, to_offset)`
-    pub fn slice_to(&self, to_offset: usize) -> FileSlice {
-        self.slice(0, to_offset)
-    }
-}
-
-impl FileHandle for FileSlice {
-    fn read_bytes(&self, from: usize, to: usize) -> io::Result<OwnedBytes> {
-        self.read_bytes_slice(from, to)
-    }
-}
-
-impl HasLen for FileSlice {
-    fn len(&self) -> usize {
-        self.stop - self.start
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::{FileHandle, FileSlice};
-    use crate::common::HasLen;
-    use std::io;
-
-    #[test]
-    fn test_file_slice() -> io::Result<()> {
-        let file_slice = FileSlice::new(Box::new(b"abcdef".as_ref()));
-        assert_eq!(file_slice.len(), 6);
-        assert_eq!(file_slice.slice_from(2).read_bytes()?.as_slice(), b"cdef");
-        assert_eq!(file_slice.slice_to(2).read_bytes()?.as_slice(), b"ab");
-        assert_eq!(
-            file_slice
-                .slice_from(1)
-                .slice_to(2)
-                .read_bytes()?
-                .as_slice(),
-            b"bc"
-        );
-        {
-            let (left, right) = file_slice.clone().split(0);
-            assert_eq!(left.read_bytes()?.as_slice(), b"");
-            assert_eq!(right.read_bytes()?.as_slice(), b"abcdef");
-        }
-        {
-            let (left, right) = file_slice.clone().split(2);
-            assert_eq!(left.read_bytes()?.as_slice(), b"ab");
-            assert_eq!(right.read_bytes()?.as_slice(), b"cdef");
-        }
-        {
-            let (left, right) = file_slice.clone().split_from_end(0);
-            assert_eq!(left.read_bytes()?.as_slice(), b"abcdef");
-            assert_eq!(right.read_bytes()?.as_slice(), b"");
-        }
-        {
-            let (left, right) = file_slice.clone().split_from_end(2);
-            assert_eq!(left.read_bytes()?.as_slice(), b"abcd");
-            assert_eq!(right.read_bytes()?.as_slice(), b"ef");
-        }
-        Ok(())
-    }
-
-    #[test]
-    fn test_file_slice_trait_slice_len() {
-        let blop: &'static [u8] = b"abc";
-        let owned_bytes: Box<dyn FileHandle> = Box::new(blop);
-        assert_eq!(owned_bytes.len(), 3);
-    }
-
-    #[test]
-    fn test_slice_simple_read() -> io::Result<()> {
-        let slice = FileSlice::new(Box::new(&b"abcdef"[..]));
-        assert_eq!(slice.len(), 6);
-        assert_eq!(slice.read_bytes()?.as_ref(), b"abcdef");
-        assert_eq!(slice.slice(1, 4).read_bytes()?.as_ref(), b"bcd");
-        Ok(())
-    }
-
-    #[test]
-    fn test_slice_read_slice() -> io::Result<()> {
-        let slice_deref = FileSlice::new(Box::new(&b"abcdef"[..]));
-        assert_eq!(slice_deref.read_bytes_slice(1, 4)?.as_ref(), b"bcd");
-        Ok(())
-    }
-
-    #[test]
-    #[should_panic(expected = "assertion failed: from <= to")]
-    fn test_slice_read_slice_invalid_range() {
-        let slice_deref = FileSlice::new(Box::new(&b"abcdef"[..]));
-        assert_eq!(slice_deref.read_bytes_slice(1, 0).unwrap().as_ref(), b"bcd");
-    }
-
-    #[test]
-    #[should_panic(expected = "`to` exceeds the fileslice length")]
-    fn test_slice_read_slice_invalid_range_exceeds() {
-        let slice_deref = FileSlice::new(Box::new(&b"abcdef"[..]));
-        assert_eq!(
-            slice_deref.read_bytes_slice(0, 10).unwrap().as_ref(),
-            b"bcd"
-        );
-    }
-}

src/directory/file_watcher.rs

@@ -1,178 +0,0 @@
-use crate::directory::{WatchCallback, WatchCallbackList, WatchHandle};
-use crc32fast::Hasher;
-use std::fs;
-use std::io;
-use std::io::BufRead;
-use std::path::Path;
-use std::sync::atomic::{AtomicUsize, Ordering};
-use std::sync::Arc;
-use std::thread;
-use std::time::Duration;
-
-pub const POLLING_INTERVAL: Duration = Duration::from_millis(if cfg!(test) { 1 } else { 500 });
-
-// Watches a file and executes registered callbacks when the file is modified.
-pub struct FileWatcher {
-    path: Arc<Path>,
-    callbacks: Arc<WatchCallbackList>,
-    state: Arc<AtomicUsize>, // 0: new, 1: runnable, 2: terminated
-}
-
-impl FileWatcher {
-    pub fn new(path: &Path) -> FileWatcher {
-        FileWatcher {
-            path: Arc::from(path),
-            callbacks: Default::default(),
-            state: Default::default(),
-        }
-    }
-
-    pub fn spawn(&self) {
-        if self.state.compare_and_swap(0, 1, Ordering::SeqCst) > 0 {
-            return;
-        }
-
-        let path = self.path.clone();
-        let callbacks = self.callbacks.clone();
-        let state = self.state.clone();
-
-        thread::Builder::new()
-            .name("thread-tantivy-meta-file-watcher".to_string())
-            .spawn(move || {
-                let mut current_checksum = None;
-
-                while state.load(Ordering::SeqCst) == 1 {
-                    if let Ok(checksum) = FileWatcher::compute_checksum(&path) {
-                        // `None.unwrap_or_else(|| !checksum) != checksum` evaluates to `true`
-                        if current_checksum.unwrap_or_else(|| !checksum) != checksum {
-                            info!("Meta file {:?} was modified", path);
-                            current_checksum = Some(checksum);
-                            futures::executor::block_on(callbacks.broadcast());
-                        }
-                    }
-
-                    thread::sleep(POLLING_INTERVAL);
-                }
-            })
-            .expect("Failed to spawn meta file watcher thread");
-    }
-
-    pub fn watch(&self, callback: WatchCallback) -> WatchHandle {
-        let handle = self.callbacks.subscribe(callback);
-        self.spawn();
-        handle
-    }
-
-    fn compute_checksum(path: &Path) -> Result<u32, io::Error> {
-        let reader = match fs::File::open(path) {
-            Ok(f) => io::BufReader::new(f),
-            Err(e) => {
-                warn!("Failed to open meta file {:?}: {:?}", path, e);
-                return Err(e);
-            }
-        };
-
-        let mut hasher = Hasher::new();
-
-        for line in reader.lines() {
-            hasher.update(line?.as_bytes())
-        }
-
-        Ok(hasher.finalize())
-    }
-}
-
-impl Drop for FileWatcher {
-    fn drop(&mut self) {
-        self.state.store(2, Ordering::SeqCst);
-    }
-}
-
-#[cfg(test)]
-mod tests {
-
-    use std::mem;
-
-    use crate::directory::mmap_directory::atomic_write;
-
-    use super::*;
-
-    #[test]
-    fn test_file_watcher_drop_watcher() -> crate::Result<()> {
-        let tmp_dir = tempfile::TempDir::new()?;
-        let tmp_file = tmp_dir.path().join("watched.txt");
-
-        let counter: Arc<AtomicUsize> = Default::default();
-        let (tx, rx) = crossbeam::channel::unbounded();
-        let timeout = Duration::from_millis(100);
-
-        let watcher = FileWatcher::new(&tmp_file);
-
-        let state = watcher.state.clone();
-        assert_eq!(state.load(Ordering::SeqCst), 0);
-
-        let counter_clone = counter.clone();
-
-        let _handle = watcher.watch(WatchCallback::new(move || {
-            let val = counter_clone.fetch_add(1, Ordering::SeqCst);
-            tx.send(val + 1).unwrap();
-        }));
-
-        assert_eq!(counter.load(Ordering::SeqCst), 0);
-        assert_eq!(state.load(Ordering::SeqCst), 1);
-
-        atomic_write(&tmp_file, b"foo")?;
-        assert_eq!(rx.recv_timeout(timeout), Ok(1));
-
-        atomic_write(&tmp_file, b"foo")?;
-        assert!(rx.recv_timeout(timeout).is_err());
-
-        atomic_write(&tmp_file, b"bar")?;
-        assert_eq!(rx.recv_timeout(timeout), Ok(2));
-
-        mem::drop(watcher);
-
-        atomic_write(&tmp_file, b"qux")?;
-        thread::sleep(Duration::from_millis(10));
-        assert_eq!(counter.load(Ordering::SeqCst), 2);
-        assert_eq!(state.load(Ordering::SeqCst), 2);
-
-        Ok(())
-    }
-
-    #[test]
-    fn test_file_watcher_drop_handle() -> crate::Result<()> {
-        let tmp_dir = tempfile::TempDir::new()?;
-        let tmp_file = tmp_dir.path().join("watched.txt");
-
-        let counter: Arc<AtomicUsize> = Default::default();
-        let (tx, rx) = crossbeam::channel::unbounded();
-        let timeout = Duration::from_millis(100);
-
-        let watcher = FileWatcher::new(&tmp_file);
-
-        let state = watcher.state.clone();
-        assert_eq!(state.load(Ordering::SeqCst), 0);
-
-        let counter_clone = counter.clone();
-
-        let handle = watcher.watch(WatchCallback::new(move || {
-            let val = counter_clone.fetch_add(1, Ordering::SeqCst);
-            tx.send(val + 1).unwrap();
-        }));
-
-        assert_eq!(counter.load(Ordering::SeqCst), 0);
-        assert_eq!(state.load(Ordering::SeqCst), 1);
-
-        atomic_write(&tmp_file, b"foo")?;
-        assert_eq!(rx.recv_timeout(timeout), Ok(1));
-
-        mem::drop(handle);
-
-        atomic_write(&tmp_file, b"qux")?;
-        assert_eq!(counter.load(Ordering::SeqCst), 1);
-        assert_eq!(state.load(Ordering::SeqCst), 1);
-
-        Ok(())
-    }
-}

src/directory/footer.rs

@@ -1,8 +1,9 @@
-use crate::common::{BinarySerializable, CountingWriter, FixedSize, HasLen, VInt};
+use crate::common::{BinarySerializable, CountingWriter, FixedSize, VInt};
 use crate::directory::error::Incompatibility;
-use crate::directory::FileSlice;
+use crate::directory::read_only_source::ReadOnlySource;
 use crate::directory::{AntiCallToken, TerminatingWrite};
 use crate::Version;
+use byteorder::{ByteOrder, LittleEndian, WriteBytesExt};
 use crc32fast::Hasher;
 use std::io;
 use std::io::Write;
@@ -63,26 +64,26 @@ impl Footer {
         let mut counting_write = CountingWriter::wrap(&mut write);
         self.serialize(&mut counting_write)?;
         let written_len = counting_write.written_bytes();
-        (written_len as u32).serialize(write)?;
+        write.write_u32::<LittleEndian>(written_len as u32)?;
         Ok(())
     }
 
-    pub fn extract_footer(file: FileSlice) -> io::Result<(Footer, FileSlice)> {
+    pub fn extract_footer(source: ReadOnlySource) -> Result<(Footer, ReadOnlySource), io::Error> {
-        if file.len() < 4 {
+        if source.len() < 4 {
             return Err(io::Error::new(
                 io::ErrorKind::UnexpectedEof,
                 format!(
                     "File corrupted. The file is smaller than 4 bytes (len={}).",
-                    file.len()
+                    source.len()
                 ),
             ));
         }
-        let (body_footer, footer_len_file) = file.split_from_end(u32::SIZE_IN_BYTES);
+        let (body_footer, footer_len_bytes) = source.split_from_end(u32::SIZE_IN_BYTES);
-        let mut footer_len_bytes = footer_len_file.read_bytes()?;
+        let footer_len = LittleEndian::read_u32(footer_len_bytes.as_slice()) as usize;
-        let footer_len = u32::deserialize(&mut footer_len_bytes)? as usize;
+        let body_len = body_footer.len() - footer_len;
-        let (body, footer) = body_footer.split_from_end(footer_len);
+        let (body, footer_data) = body_footer.split(body_len);
-        let mut footer_bytes = footer.read_bytes()?;
+        let mut cursor = footer_data.as_slice();
-        let footer = Footer::deserialize(&mut footer_bytes)?;
+        let footer = Footer::deserialize(&mut cursor)?;
         Ok((footer, body))
     }
 
@@ -93,36 +94,12 @@ impl Footer {
         match &self.versioned_footer {
             VersionedFooter::V1 {
                 crc32: _crc,
-                store_compression,
+                store_compression: compression,
             } => {
-                if &library_version.store_compression != store_compression {
+                if &library_version.store_compression != compression {
                     return Err(Incompatibility::CompressionMismatch {
                         library_compression_format: library_version.store_compression.to_string(),
-                        index_compression_format: store_compression.to_string(),
+                        index_compression_format: compression.to_string(),
-                    });
-                }
-                Ok(())
-            }
-            VersionedFooter::V2 {
-                crc32: _crc,
-                store_compression,
-            } => {
-                if &library_version.store_compression != store_compression {
-                    return Err(Incompatibility::CompressionMismatch {
-                        library_compression_format: library_version.store_compression.to_string(),
-                        index_compression_format: store_compression.to_string(),
-                    });
-                }
-                Ok(())
-            }
-            VersionedFooter::V3 {
-                crc32: _crc,
-                store_compression,
-            } => {
-                if &library_version.store_compression != store_compression {
-                    return Err(Incompatibility::CompressionMismatch {
-                        library_compression_format: library_version.store_compression.to_string(),
-                        index_compression_format: store_compression.to_string(),
                     });
                 }
                 Ok(())
@@ -143,36 +120,24 @@ pub enum VersionedFooter {
         crc32: CrcHashU32,
         store_compression: String,
     },
-    // Introduction of the Block WAND information.
-    V2 {
-        crc32: CrcHashU32,
-        store_compression: String,
-    },
-    // Block wand max termfred on 1 byte
-    V3 {
-        crc32: CrcHashU32,
-        store_compression: String,
-    },
 }
 
 impl BinarySerializable for VersionedFooter {
     fn serialize<W: io::Write>(&self, writer: &mut W) -> io::Result<()> {
         let mut buf = Vec::new();
         match self {
-            VersionedFooter::V3 {
+            VersionedFooter::V1 {
                 crc32,
                 store_compression: compression,
             } => {
                 // Serializes a valid `VersionedFooter` or panics if the version is unknown
                 // [   version    |   crc_hash  | compression_mode ]
                 // [    0..4      |     4..8    |     variable     ]
-                BinarySerializable::serialize(&3u32, &mut buf)?;
+                BinarySerializable::serialize(&1u32, &mut buf)?;
                 BinarySerializable::serialize(crc32, &mut buf)?;
                 BinarySerializable::serialize(compression, &mut buf)?;
             }
-            VersionedFooter::V2 { .. }
+            VersionedFooter::UnknownVersion => {
-            | VersionedFooter::V1 { .. }
-            | VersionedFooter::UnknownVersion => {
                 return Err(io::Error::new(
                     io::ErrorKind::InvalidInput,
                     "Cannot serialize an unknown versioned footer ",
@@ -201,36 +166,22 @@ impl BinarySerializable for VersionedFooter {
         reader.read_exact(&mut buf[..])?;
         let mut cursor = &buf[..];
         let version = u32::deserialize(&mut cursor)?;
-        if version > 3 {
+        if version == 1 {
-            return Ok(VersionedFooter::UnknownVersion);
+            let crc32 = u32::deserialize(&mut cursor)?;
-        }
+            let compression = String::deserialize(&mut cursor)?;
-        let crc32 = u32::deserialize(&mut cursor)?;
+            Ok(VersionedFooter::V1 {
-        let store_compression = String::deserialize(&mut cursor)?;
-        Ok(if version == 1 {
-            VersionedFooter::V1 {
                 crc32,
-                store_compression,
+                store_compression: compression,
-            }
+            })
-        } else if version == 2 {
-            VersionedFooter::V2 {
-                crc32,
-                store_compression,
-            }
         } else {
-            assert_eq!(version, 3);
+            Ok(VersionedFooter::UnknownVersion)
-            VersionedFooter::V3 {
+        }
-                crc32,
-                store_compression,
-            }
-        })
     }
 }
 
 impl VersionedFooter {
     pub fn crc(&self) -> Option<CrcHashU32> {
         match self {
-            VersionedFooter::V3 { crc32, .. } => Some(*crc32),
-            VersionedFooter::V2 { crc32, .. } => Some(*crc32),
             VersionedFooter::V1 { crc32, .. } => Some(*crc32),
             VersionedFooter::UnknownVersion { .. } => None,
         }
@@ -268,7 +219,7 @@ impl<W: TerminatingWrite> Write for FooterProxy<W> {
 impl<W: TerminatingWrite> TerminatingWrite for FooterProxy<W> {
     fn terminate_ref(&mut self, _: AntiCallToken) -> io::Result<()> {
         let crc32 = self.hasher.take().unwrap().finalize();
-        let footer = Footer::new(VersionedFooter::V3 {
+        let footer = Footer::new(VersionedFooter::V1 {
             crc32,
             store_compression: crate::store::COMPRESSION.to_string(),
         });
@@ -295,17 +246,17 @@ mod tests {
         let mut vec = Vec::new();
         let footer_proxy = FooterProxy::new(&mut vec);
         assert!(footer_proxy.terminate().is_ok());
-        if crate::store::COMPRESSION == "lz4" {
+        assert_eq!(vec.len(), 167);
-            assert_eq!(vec.len(), 158);
-        } else {
-            assert_eq!(vec.len(), 167);
-        }
         let footer = Footer::deserialize(&mut &vec[..]).unwrap();
-        assert!(matches!(
+        if let VersionedFooter::V1 {
-           footer.versioned_footer,
+            crc32: _,
-           VersionedFooter::V3 { store_compression, .. }
+            store_compression,
-           if store_compression == crate::store::COMPRESSION
+        } = footer.versioned_footer
-        ));
+        {
+            assert_eq!(store_compression, crate::store::COMPRESSION);
+        } else {
+            panic!("Versioned footer should be V1.");
+        }
         assert_eq!(&footer.version, crate::version());
     }
 
@@ -313,7 +264,7 @@ mod tests {
     fn test_serialize_deserialize_footer() {
         let mut buffer = Vec::new();
         let crc32 = 123456u32;
-        let footer: Footer = Footer::new(VersionedFooter::V3 {
+        let footer: Footer = Footer::new(VersionedFooter::V1 {
             crc32,
             store_compression: "lz4".to_string(),
         });
@@ -325,7 +276,7 @@ mod tests {
     #[test]
     fn footer_length() {
         let crc32 = 1111111u32;
-        let versioned_footer = VersionedFooter::V3 {
+        let versioned_footer = VersionedFooter::V1 {
             crc32,
             store_compression: "lz4".to_string(),
         };
@@ -346,7 +297,7 @@ mod tests {
             // versionned footer length
             12 | 128,
             // index format version
-            3,
+            1,
             0,
             0,
             0,
@@ -365,7 +316,7 @@ mod tests {
         let versioned_footer = VersionedFooter::deserialize(&mut cursor).unwrap();
         assert!(cursor.is_empty());
         let expected_crc: u32 = LittleEndian::read_u32(&v_footer_bytes[5..9]) as CrcHashU32;
-        let expected_versioned_footer: VersionedFooter = VersionedFooter::V3 {
+        let expected_versioned_footer: VersionedFooter = VersionedFooter::V1 {
             crc32: expected_crc,
             store_compression: "lz4".to_string(),
         };

src/directory/managed_directory.rs

@@ -1,16 +1,17 @@
-use crate::core::{MANAGED_FILEPATH, META_FILEPATH};
+use crate::core::MANAGED_FILEPATH;
-use crate::directory::error::{DeleteError, LockError, OpenReadError, OpenWriteError};
+use crate::directory::error::{DeleteError, IOError, LockError, OpenReadError, OpenWriteError};
 use crate::directory::footer::{Footer, FooterProxy};
+use crate::directory::DirectoryLock;
 use crate::directory::GarbageCollectionResult;
 use crate::directory::Lock;
 use crate::directory::META_LOCK;
-use crate::directory::{DirectoryLock, FileHandle};
+use crate::directory::{ReadOnlySource, WritePtr};
-use crate::directory::{FileSlice, WritePtr};
 use crate::directory::{WatchCallback, WatchHandle};
 use crate::error::DataCorruption;
 use crate::Directory;
 
 use crc32fast::Hasher;
+use serde_json;
 use std::collections::HashSet;
 use std::io;
 use std::io::Write;
@@ -53,7 +54,7 @@ struct MetaInformation {
 /// Saves the file containing the list of existing files
 /// that were created by tantivy.
 fn save_managed_paths(
-    directory: &dyn Directory,
+    directory: &mut dyn Directory,
     wlock: &RwLockWriteGuard<'_, MetaInformation>,
 ) -> io::Result<()> {
     let mut w = serde_json::to_vec(&wlock.managed_paths)?;
@@ -86,7 +87,7 @@ impl ManagedDirectory {
                 directory: Box::new(directory),
                 meta_informations: Arc::default(),
             }),
-            io_err @ Err(OpenReadError::IOError { .. }) => Err(io_err.err().unwrap().into()),
+            Err(OpenReadError::IOError(e)) => Err(From::from(e)),
             Err(OpenReadError::IncompatibleIndex(incompatibility)) => {
                 // For the moment, this should never happen  `meta.json`
                 // do not have any footer and cannot detect incompatibility.
@@ -168,7 +169,7 @@ impl ManagedDirectory {
                         DeleteError::FileDoesNotExist(_) => {
                             deleted_files.push(file_to_delete.clone());
                         }
-                        DeleteError::IOError { .. } => {
+                        DeleteError::IOError(_) => {
                             failed_to_delete_files.push(file_to_delete.clone());
                             if !cfg!(target_os = "windows") {
                                 // On windows, delete is expected to fail if the file
@@ -212,7 +213,7 @@ impl ManagedDirectory {
     /// File starting by "." are reserved to locks.
     /// They are not managed and cannot be subjected
     /// to garbage collection.
-    fn register_file_as_managed(&self, filepath: &Path) -> io::Result<()> {
+    fn register_file_as_managed(&mut self, filepath: &Path) -> io::Result<()> {
         // Files starting by "." (e.g. lock files) are not managed.
         if !is_managed(filepath) {
             return Ok(());
@@ -223,7 +224,7 @@ impl ManagedDirectory {
             .expect("Managed file lock poisoned");
         let has_changed = meta_wlock.managed_paths.insert(filepath.to_owned());
         if has_changed {
-            save_managed_paths(self.directory.as_ref(), &meta_wlock)?;
+            save_managed_paths(self.directory.as_mut(), &meta_wlock)?;
         }
         Ok(())
     }
@@ -231,19 +232,10 @@ impl ManagedDirectory {
     /// Verify checksum of a managed file
     pub fn validate_checksum(&self, path: &Path) -> result::Result<bool, OpenReadError> {
         let reader = self.directory.open_read(path)?;
-        let (footer, data) =
+        let (footer, data) = Footer::extract_footer(reader)
-            Footer::extract_footer(reader).map_err(|io_error| OpenReadError::IOError {
+            .map_err(|err| IOError::with_path(path.to_path_buf(), err))?;
-                io_error,
-                filepath: path.to_path_buf(),
-            })?;
-        let bytes = data
-            .read_bytes()
-            .map_err(|io_error| OpenReadError::IOError {
-                filepath: path.to_path_buf(),
-                io_error,
-            })?;
         let mut hasher = Hasher::new();
-        hasher.update(bytes.as_slice());
+        hasher.update(data.as_slice());
         let crc = hasher.finalize();
         Ok(footer
             .versioned_footer
@@ -254,42 +246,35 @@ impl ManagedDirectory {
 
     /// List files for which checksum does not match content
     pub fn list_damaged(&self) -> result::Result<HashSet<PathBuf>, OpenReadError> {
-        let mut managed_paths = self
+        let mut hashset = HashSet::new();
+        let managed_paths = self
             .meta_informations
             .read()
             .expect("Managed directory rlock poisoned in list damaged.")
             .managed_paths
             .clone();
 
-        managed_paths.remove(*META_FILEPATH);
+        for path in managed_paths.into_iter() {
-
-        let mut damaged_files = HashSet::new();
-        for path in managed_paths {
             if !self.validate_checksum(&path)? {
-                damaged_files.insert(path);
+                hashset.insert(path);
             }
         }
-        Ok(damaged_files)
+        Ok(hashset)
     }
 }
 
 impl Directory for ManagedDirectory {
-    fn get_file_handle(&self, path: &Path) -> Result<Box<dyn FileHandle>, OpenReadError> {
+    fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
-        let file_slice = self.open_read(path)?;
+        let read_only_source = self.directory.open_read(path)?;
-        Ok(Box::new(file_slice))
+        let (footer, reader) = Footer::extract_footer(read_only_source)
-    }
+            .map_err(|err| IOError::with_path(path.to_path_buf(), err))?;
-
-    fn open_read(&self, path: &Path) -> result::Result<FileSlice, OpenReadError> {
-        let file_slice = self.directory.open_read(path)?;
-        let (footer, reader) = Footer::extract_footer(file_slice)
-            .map_err(|io_error| OpenReadError::wrap_io_error(io_error, path.to_path_buf()))?;
         footer.is_compatible()?;
         Ok(reader)
     }
 
-    fn open_write(&self, path: &Path) -> result::Result<WritePtr, OpenWriteError> {
+    fn open_write(&mut self, path: &Path) -> result::Result<WritePtr, OpenWriteError> {
         self.register_file_as_managed(path)
-            .map_err(|io_error| OpenWriteError::wrap_io_error(io_error, path.to_path_buf()))?;
+            .map_err(|e| IOError::with_path(path.to_owned(), e))?;
         Ok(io::BufWriter::new(Box::new(FooterProxy::new(
             self.directory
                 .open_write(path)?
@@ -299,7 +284,7 @@ impl Directory for ManagedDirectory {
         ))))
     }
 
-    fn atomic_write(&self, path: &Path, data: &[u8]) -> io::Result<()> {
+    fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
         self.register_file_as_managed(path)?;
         self.directory.atomic_write(path, data)
     }
@@ -312,7 +297,7 @@ impl Directory for ManagedDirectory {
         self.directory.delete(path)
     }
 
-    fn exists(&self, path: &Path) -> Result<bool, OpenReadError> {
+    fn exists(&self, path: &Path) -> bool {
         self.directory.exists(path)
     }
 
@@ -360,22 +345,22 @@ mod tests_mmap_specific {
             managed_directory
                 .atomic_write(test_path2, &[0u8, 1u8])
                 .unwrap();
-            assert!(managed_directory.exists(test_path1).unwrap());
+            assert!(managed_directory.exists(test_path1));
-            assert!(managed_directory.exists(test_path2).unwrap());
+            assert!(managed_directory.exists(test_path2));
             let living_files: HashSet<PathBuf> = [test_path1.to_owned()].iter().cloned().collect();
             assert!(managed_directory.garbage_collect(|| living_files).is_ok());
-            assert!(managed_directory.exists(test_path1).unwrap());
+            assert!(managed_directory.exists(test_path1));
-            assert!(!managed_directory.exists(test_path2).unwrap());
+            assert!(!managed_directory.exists(test_path2));
         }
         {
             let mmap_directory = MmapDirectory::open(&tempdir_path).unwrap();
             let mut managed_directory = ManagedDirectory::wrap(mmap_directory).unwrap();
-            assert!(managed_directory.exists(test_path1).unwrap());
+            assert!(managed_directory.exists(test_path1));
-            assert!(!managed_directory.exists(test_path2).unwrap());
+            assert!(!managed_directory.exists(test_path2));
             let living_files: HashSet<PathBuf> = HashSet::new();
             assert!(managed_directory.garbage_collect(|| living_files).is_ok());
-            assert!(!managed_directory.exists(test_path1).unwrap());
+            assert!(!managed_directory.exists(test_path1));
-            assert!(!managed_directory.exists(test_path2).unwrap());
+            assert!(!managed_directory.exists(test_path2));
         }
     }
 
@@ -392,7 +377,7 @@ mod tests_mmap_specific {
         let mut write = managed_directory.open_write(test_path1).unwrap();
         write.write_all(&[0u8, 1u8]).unwrap();
         write.terminate().unwrap();
-        assert!(managed_directory.exists(test_path1).unwrap());
+        assert!(managed_directory.exists(test_path1));
 
         let _mmap_read = managed_directory.open_read(test_path1).unwrap();
         assert!(managed_directory
@@ -400,50 +385,52 @@ mod tests_mmap_specific {
             .is_ok());
         if cfg!(target_os = "windows") {
             // On Windows, gc should try and fail the file as it is mmapped.
-            assert!(managed_directory.exists(test_path1).unwrap());
+            assert!(managed_directory.exists(test_path1));
             // unmap should happen here.
             drop(_mmap_read);
             // The file should still be in the list of managed file and
             // eventually be deleted once mmap is released.
             assert!(managed_directory.garbage_collect(|| living_files).is_ok());
-            assert!(!managed_directory.exists(test_path1).unwrap());
+            assert!(!managed_directory.exists(test_path1));
         } else {
-            assert!(!managed_directory.exists(test_path1).unwrap());
+            assert!(!managed_directory.exists(test_path1));
         }
     }
 
     #[test]
-    fn test_checksum() -> crate::Result<()> {
+    fn test_checksum() {
         let test_path1: &'static Path = Path::new("some_path_for_test");
         let test_path2: &'static Path = Path::new("other_test_path");
 
         let tempdir = TempDir::new().unwrap();
         let tempdir_path = PathBuf::from(tempdir.path());
 
-        let mmap_directory = MmapDirectory::open(&tempdir_path)?;
+        let mmap_directory = MmapDirectory::open(&tempdir_path).unwrap();
-        let managed_directory = ManagedDirectory::wrap(mmap_directory)?;
+        let mut managed_directory = ManagedDirectory::wrap(mmap_directory).unwrap();
-        let mut write = managed_directory.open_write(test_path1)?;
+        let mut write = managed_directory.open_write(test_path1).unwrap();
-        write.write_all(&[0u8, 1u8])?;
+        write.write_all(&[0u8, 1u8]).unwrap();
-        write.terminate()?;
+        write.terminate().unwrap();
 
-        let mut write = managed_directory.open_write(test_path2)?;
+        let mut write = managed_directory.open_write(test_path2).unwrap();
-        write.write_all(&[3u8, 4u8, 5u8])?;
+        write.write_all(&[3u8, 4u8, 5u8]).unwrap();
-        write.terminate()?;
+        write.terminate().unwrap();
 
-        let read_file = managed_directory.open_read(test_path2)?.read_bytes()?;
+        let read_source = managed_directory.open_read(test_path2).unwrap();
-        assert_eq!(read_file.as_slice(), &[3u8, 4u8, 5u8]);
+        assert_eq!(read_source.as_slice(), &[3u8, 4u8, 5u8]);
         assert!(managed_directory.list_damaged().unwrap().is_empty());
 
         let mut corrupted_path = tempdir_path.clone();
         corrupted_path.push(test_path2);
-        let mut file = OpenOptions::new().write(true).open(&corrupted_path)?;
+        let mut file = OpenOptions::new()
-        file.write_all(&[255u8])?;
+            .write(true)
-        file.flush()?;
+            .open(&corrupted_path)
+            .unwrap();
+        file.write_all(&[255u8]).unwrap();
+        file.flush().unwrap();
         drop(file);
 
-        let damaged = managed_directory.list_damaged()?;
+        let damaged = managed_directory.list_damaged().unwrap();
         assert_eq!(damaged.len(), 1);
         assert!(damaged.contains(test_path2));
-        Ok(())
     }
 }

src/directory/mmap_directory.rs

@@ -1,19 +1,29 @@
+use fs2;
+use notify;
+
+use self::fs2::FileExt;
+use self::notify::RawEvent;
+use self::notify::RecursiveMode;
+use self::notify::Watcher;
 use crate::core::META_FILEPATH;
 use crate::directory::error::LockError;
-use crate::directory::error::{DeleteError, OpenDirectoryError, OpenReadError, OpenWriteError};
+use crate::directory::error::{
-use crate::directory::file_watcher::FileWatcher;
+    DeleteError, IOError, OpenDirectoryError, OpenReadError, OpenWriteError,
+};
+use crate::directory::read_only_source::BoxedData;
+use crate::directory::AntiCallToken;
 use crate::directory::Directory;
 use crate::directory::DirectoryLock;
 use crate::directory::Lock;
+use crate::directory::ReadOnlySource;
 use crate::directory::WatchCallback;
+use crate::directory::WatchCallbackList;
 use crate::directory::WatchHandle;
-use crate::directory::{AntiCallToken, FileHandle, OwnedBytes};
-use crate::directory::{ArcBytes, WeakArcBytes};
 use crate::directory::{TerminatingWrite, WritePtr};
-use fs2::FileExt;
+use atomicwrites;
 use memmap::Mmap;
 use serde::{Deserialize, Serialize};
-use stable_deref_trait::StableDeref;
+use std::collections::HashMap;
 use std::convert::From;
 use std::fmt;
 use std::fs::OpenOptions;
@@ -22,9 +32,12 @@ use std::io::{self, Seek, SeekFrom};
 use std::io::{BufWriter, Read, Write};
 use std::path::{Path, PathBuf};
 use std::result;
+use std::sync::mpsc::{channel, Receiver, Sender};
 use std::sync::Arc;
+use std::sync::Mutex;
 use std::sync::RwLock;
-use std::{collections::HashMap, ops::Deref};
+use std::sync::Weak;
+use std::thread;
 use tempfile::TempDir;
 
 /// Create a default io error given a string.
@@ -35,17 +48,17 @@ pub(crate) fn make_io_err(msg: String) -> io::Error {
 /// Returns None iff the file exists, can be read, but is empty (and hence
 /// cannot be mmapped)
 fn open_mmap(full_path: &Path) -> result::Result<Option<Mmap>, OpenReadError> {
-    let file = File::open(full_path).map_err(|io_err| {
+    let file = File::open(full_path).map_err(|e| {
-        if io_err.kind() == io::ErrorKind::NotFound {
+        if e.kind() == io::ErrorKind::NotFound {
-            OpenReadError::FileDoesNotExist(full_path.to_path_buf())
+            OpenReadError::FileDoesNotExist(full_path.to_owned())
         } else {
-            OpenReadError::wrap_io_error(io_err, full_path.to_path_buf())
+            OpenReadError::IOError(IOError::with_path(full_path.to_owned(), e))
         }
     })?;
 
     let meta_data = file
         .metadata()
-        .map_err(|io_err| OpenReadError::wrap_io_error(io_err, full_path.to_owned()))?;
+        .map_err(|e| IOError::with_path(full_path.to_owned(), e))?;
     if meta_data.len() == 0 {
         // if the file size is 0, it will not be possible
         // to mmap the file, so we return None
@@ -55,7 +68,7 @@ fn open_mmap(full_path: &Path) -> result::Result<Option<Mmap>, OpenReadError> {
     unsafe {
         memmap::Mmap::map(&file)
             .map(Some)
-            .map_err(|io_err| OpenReadError::wrap_io_error(io_err, full_path.to_path_buf()))
+            .map_err(|e| From::from(IOError::with_path(full_path.to_owned(), e)))
     }
 }
 
@@ -76,7 +89,7 @@ pub struct CacheInfo {
 
 struct MmapCache {
     counters: CacheCounters,
-    cache: HashMap<PathBuf, WeakArcBytes>,
+    cache: HashMap<PathBuf, Weak<BoxedData>>,
 }
 
 impl Default for MmapCache {
@@ -110,7 +123,7 @@ impl MmapCache {
     }
 
     // Returns None if the file exists but as a len of 0 (and hence is not mmappable).
-    fn get_mmap(&mut self, full_path: &Path) -> Result<Option<ArcBytes>, OpenReadError> {
+    fn get_mmap(&mut self, full_path: &Path) -> Result<Option<Arc<BoxedData>>, OpenReadError> {
         if let Some(mmap_weak) = self.cache.get(full_path) {
             if let Some(mmap_arc) = mmap_weak.upgrade() {
                 self.counters.hit += 1;
@@ -121,7 +134,7 @@ impl MmapCache {
         self.counters.miss += 1;
         let mmap_opt = open_mmap(full_path)?;
         Ok(mmap_opt.map(|mmap| {
-            let mmap_arc: ArcBytes = Arc::new(mmap);
+            let mmap_arc: Arc<BoxedData> = Arc::new(Box::new(mmap));
             let mmap_weak = Arc::downgrade(&mmap_arc);
             self.cache.insert(full_path.to_owned(), mmap_weak);
             mmap_arc
@@ -129,6 +142,63 @@ impl MmapCache {
     }
 }
 
+struct WatcherWrapper {
+    _watcher: Mutex<notify::RecommendedWatcher>,
+    watcher_router: Arc<WatchCallbackList>,
+}
+
+impl WatcherWrapper {
+    pub fn new(path: &Path) -> Result<Self, OpenDirectoryError> {
+        let (tx, watcher_recv): (Sender<RawEvent>, Receiver<RawEvent>) = channel();
+        // We need to initialize the
+        let watcher = notify::raw_watcher(tx)
+            .and_then(|mut watcher| {
+                watcher.watch(path, RecursiveMode::Recursive)?;
+                Ok(watcher)
+            })
+            .map_err(|err| match err {
+                notify::Error::PathNotFound => OpenDirectoryError::DoesNotExist(path.to_owned()),
+                _ => {
+                    panic!("Unknown error while starting watching directory {:?}", path);
+                }
+            })?;
+        let watcher_router: Arc<WatchCallbackList> = Default::default();
+        let watcher_router_clone = watcher_router.clone();
+        thread::Builder::new()
+            .name("meta-file-watch-thread".to_string())
+            .spawn(move || {
+                loop {
+                    match watcher_recv.recv().map(|evt| evt.path) {
+                        Ok(Some(changed_path)) => {
+                            // ... Actually subject to false positive.
+                            // We might want to be more accurate than this at one point.
+                            if let Some(filename) = changed_path.file_name() {
+                                if filename == *META_FILEPATH {
+                                    let _ = watcher_router_clone.broadcast();
+                                }
+                            }
+                        }
+                        Ok(None) => {
+                            // not an event we are interested in.
+                        }
+                        Err(_e) => {
+                            // the watch send channel was dropped
+                            break;
+                        }
+                    }
+                }
+            })?;
+        Ok(WatcherWrapper {
+            _watcher: Mutex::new(watcher),
+            watcher_router,
+        })
+    }
+
+    pub fn watch(&mut self, watch_callback: WatchCallback) -> WatchHandle {
+        self.watcher_router.subscribe(watch_callback)
+    }
+}
+
 /// Directory storing data in files, read via mmap.
 ///
 /// The Mmap object are cached to limit the
@@ -150,21 +220,44 @@ struct MmapDirectoryInner {
     root_path: PathBuf,
     mmap_cache: RwLock<MmapCache>,
     _temp_directory: Option<TempDir>,
-    watcher: FileWatcher,
+    watcher: RwLock<Option<WatcherWrapper>>,
 }
 
 impl MmapDirectoryInner {
-    fn new(root_path: PathBuf, temp_directory: Option<TempDir>) -> MmapDirectoryInner {
+    fn new(
-        MmapDirectoryInner {
+        root_path: PathBuf,
+        temp_directory: Option<TempDir>,
+    ) -> Result<MmapDirectoryInner, OpenDirectoryError> {
+        let mmap_directory_inner = MmapDirectoryInner {
+            root_path,
             mmap_cache: Default::default(),
             _temp_directory: temp_directory,
-            watcher: FileWatcher::new(&root_path.join(*META_FILEPATH)),
+            watcher: RwLock::new(None),
-            root_path,
+        };
-        }
+        Ok(mmap_directory_inner)
     }
 
-    fn watch(&self, callback: WatchCallback) -> crate::Result<WatchHandle> {
+    fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle> {
-        Ok(self.watcher.watch(callback))
+        // a lot of juggling here, to ensure we don't do anything that panics
+        // while the rwlock is held. That way we ensure that the rwlock cannot
+        // be poisoned.
+        //
+        // The downside is that we might create a watch wrapper that is not useful.
+        let need_initialization = self.watcher.read().unwrap().is_none();
+        if need_initialization {
+            let watch_wrapper = WatcherWrapper::new(&self.root_path)?;
+            let mut watch_wlock = self.watcher.write().unwrap();
+            // the watcher could have been initialized when we released the lock, and
+            // we do not want to lose the watched files that were set.
+            if watch_wlock.is_none() {
+                *watch_wlock = Some(watch_wrapper);
+            }
+        }
+        if let Some(watch_wrapper) = self.watcher.write().unwrap().as_mut() {
+            Ok(watch_wrapper.watch(watch_callback))
+        } else {
+            unreachable!("At this point, watch wrapper is supposed to be initialized");
+        }
     }
 }
 
@@ -175,11 +268,14 @@ impl fmt::Debug for MmapDirectory {
 }
 
 impl MmapDirectory {
-    fn new(root_path: PathBuf, temp_directory: Option<TempDir>) -> MmapDirectory {
+    fn new(
-        let inner = MmapDirectoryInner::new(root_path, temp_directory);
+        root_path: PathBuf,
-        MmapDirectory {
+        temp_directory: Option<TempDir>,
+    ) -> Result<MmapDirectory, OpenDirectoryError> {
+        let inner = MmapDirectoryInner::new(root_path, temp_directory)?;
+        Ok(MmapDirectory {
             inner: Arc::new(inner),
-        }
+        })
     }
 
     /// Creates a new MmapDirectory in a temporary directory.
@@ -187,11 +283,9 @@ impl MmapDirectory {
     /// This is mostly useful to test the MmapDirectory itself.
     /// For your unit tests, prefer the RAMDirectory.
     pub fn create_from_tempdir() -> Result<MmapDirectory, OpenDirectoryError> {
-        let tempdir = TempDir::new().map_err(OpenDirectoryError::FailedToCreateTempDir)?;
+        let tempdir = TempDir::new().map_err(OpenDirectoryError::IoError)?;
-        Ok(MmapDirectory::new(
+        let tempdir_path = PathBuf::from(tempdir.path());
-            tempdir.path().to_path_buf(),
+        MmapDirectory::new(tempdir_path, Some(tempdir))
-            Some(tempdir),
-        ))
     }
 
     /// Opens a MmapDirectory in a directory.
@@ -209,7 +303,7 @@ impl MmapDirectory {
                 directory_path,
             )))
         } else {
-            Ok(MmapDirectory::new(PathBuf::from(directory_path), None))
+            Ok(MmapDirectory::new(PathBuf::from(directory_path), None)?)
         }
     }
 
@@ -313,38 +407,8 @@ impl TerminatingWrite for SafeFileWriter {
     }
 }
 
-#[derive(Clone)]
-struct MmapArc(Arc<dyn Deref<Target = [u8]> + Send + Sync>);
-
-impl Deref for MmapArc {
-    type Target = [u8];
-
-    fn deref(&self) -> &[u8] {
-        self.0.deref()
-    }
-}
-unsafe impl StableDeref for MmapArc {}
-
-/// Writes a file in an atomic manner.
-pub(crate) fn atomic_write(path: &Path, content: &[u8]) -> io::Result<()> {
-    // We create the temporary file in the same directory as the target file.
-    // Indeed the canonical temp directory and the target file might sit in different
-    // filesystem, in which case the atomic write may actually not work.
-    let parent_path = path.parent().ok_or_else(|| {
-        io::Error::new(
-            io::ErrorKind::InvalidInput,
-            "Path {:?} does not have parent directory.",
-        )
-    })?;
-    let mut tempfile = tempfile::Builder::new().tempfile_in(&parent_path)?;
-    tempfile.write_all(content)?;
-    tempfile.flush()?;
-    tempfile.into_temp_path().persist(path)?;
-    Ok(())
-}
-
 impl Directory for MmapDirectory {
-    fn get_file_handle(&self, path: &Path) -> result::Result<Box<dyn FileHandle>, OpenReadError> {
+    fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
         debug!("Open Read {:?}", path);
         let full_path = self.resolve_path(path);
 
@@ -354,19 +418,12 @@ impl Directory for MmapDirectory {
                  on mmap cache while reading {:?}",
                 path
             );
-            let io_err = make_io_err(msg);
+            IOError::with_path(path.to_owned(), make_io_err(msg))
-            OpenReadError::wrap_io_error(io_err, path.to_path_buf())
         })?;
-
+        Ok(mmap_cache
-        let owned_bytes = mmap_cache
             .get_mmap(&full_path)?
-            .map(|mmap_arc| {
+            .map(ReadOnlySource::from)
-                let mmap_arc_obj = MmapArc(mmap_arc);
+            .unwrap_or_else(ReadOnlySource::empty))
-                OwnedBytes::new(mmap_arc_obj)
-            })
-            .unwrap_or_else(OwnedBytes::empty);
-
-        Ok(Box::new(owned_bytes))
     }
 
     /// Any entry associated to the path in the mmap will be
@@ -374,29 +431,25 @@ impl Directory for MmapDirectory {
     fn delete(&self, path: &Path) -> result::Result<(), DeleteError> {
         let full_path = self.resolve_path(path);
         match fs::remove_file(&full_path) {
-            Ok(_) => self.sync_directory().map_err(|e| DeleteError::IOError {
+            Ok(_) => self
-                io_error: e,
+                .sync_directory()
-                filepath: path.to_path_buf(),
+                .map_err(|e| IOError::with_path(path.to_owned(), e).into()),
-            }),
             Err(e) => {
                 if e.kind() == io::ErrorKind::NotFound {
                     Err(DeleteError::FileDoesNotExist(path.to_owned()))
                 } else {
-                    Err(DeleteError::IOError {
+                    Err(IOError::with_path(path.to_owned(), e).into())
-                        io_error: e,
-                        filepath: path.to_path_buf(),
-                    })
                 }
             }
         }
     }
 
-    fn exists(&self, path: &Path) -> Result<bool, OpenReadError> {
+    fn exists(&self, path: &Path) -> bool {
         let full_path = self.resolve_path(path);
-        Ok(full_path.exists())
+        full_path.exists()
     }
 
-    fn open_write(&self, path: &Path) -> Result<WritePtr, OpenWriteError> {
+    fn open_write(&mut self, path: &Path) -> Result<WritePtr, OpenWriteError> {
         debug!("Open Write {:?}", path);
         let full_path = self.resolve_path(path);
 
@@ -405,22 +458,22 @@ impl Directory for MmapDirectory {
             .create_new(true)
             .open(full_path);
 
-        let mut file = open_res.map_err(|io_err| {
+        let mut file = open_res.map_err(|err| {
-            if io_err.kind() == io::ErrorKind::AlreadyExists {
+            if err.kind() == io::ErrorKind::AlreadyExists {
-                OpenWriteError::FileAlreadyExists(path.to_path_buf())
+                OpenWriteError::FileAlreadyExists(path.to_owned())
             } else {
-                OpenWriteError::wrap_io_error(io_err, path.to_path_buf())
+                IOError::with_path(path.to_owned(), err).into()
             }
         })?;
 
         // making sure the file is created.
         file.flush()
-            .map_err(|io_error| OpenWriteError::wrap_io_error(io_error, path.to_path_buf()))?;
+            .map_err(|e| IOError::with_path(path.to_owned(), e))?;
 
         // Apparetntly, on some filesystem syncing the parent
         // directory is required.
         self.sync_directory()
-            .map_err(|io_err| OpenWriteError::wrap_io_error(io_err, path.to_path_buf()))?;
+            .map_err(|e| IOError::with_path(path.to_owned(), e))?;
 
         let writer = SafeFileWriter::new(file);
         Ok(BufWriter::new(Box::new(writer)))
@@ -431,26 +484,26 @@ impl Directory for MmapDirectory {
         let mut buffer = Vec::new();
         match File::open(&full_path) {
             Ok(mut file) => {
-                file.read_to_end(&mut buffer).map_err(|io_error| {
+                file.read_to_end(&mut buffer)
-                    OpenReadError::wrap_io_error(io_error, path.to_path_buf())
+                    .map_err(|e| IOError::with_path(path.to_owned(), e))?;
-                })?;
                 Ok(buffer)
             }
-            Err(io_error) => {
+            Err(e) => {
-                if io_error.kind() == io::ErrorKind::NotFound {
+                if e.kind() == io::ErrorKind::NotFound {
                     Err(OpenReadError::FileDoesNotExist(path.to_owned()))
                 } else {
-                    Err(OpenReadError::wrap_io_error(io_error, path.to_path_buf()))
+                    Err(IOError::with_path(path.to_owned(), e).into())
                 }
             }
         }
     }
 
-    fn atomic_write(&self, path: &Path, content: &[u8]) -> io::Result<()> {
+    fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
         debug!("Atomic Write {:?}", path);
         let full_path = self.resolve_path(path);
-        atomic_write(&full_path, content)?;
+        let meta_file = atomicwrites::AtomicFile::new(full_path, atomicwrites::AllowOverwrite);
-        self.sync_directory()
+        meta_file.write(|f| f.write_all(data))?;
+        Ok(())
     }
 
     fn acquire_lock(&self, lock: &Lock) -> Result<DirectoryLock, LockError> {
@@ -485,10 +538,12 @@ mod tests {
     // The following tests are specific to the MmapDirectory
 
     use super::*;
+    use crate::indexer::LogMergePolicy;
     use crate::schema::{Schema, SchemaBuilder, TEXT};
     use crate::Index;
     use crate::ReloadPolicy;
-    use crate::{common::HasLen, indexer::LogMergePolicy};
+    use std::fs;
+    use std::sync::atomic::{AtomicUsize, Ordering};
 
     #[test]
     fn test_open_non_existent_path() {
@@ -501,7 +556,7 @@ mod tests {
         // cannot be mmapped.
         //
         // In that case the directory returns a SharedVecSlice.
-        let mmap_directory = MmapDirectory::create_from_tempdir().unwrap();
+        let mut mmap_directory = MmapDirectory::create_from_tempdir().unwrap();
         let path = PathBuf::from("test");
         {
             let mut w = mmap_directory.open_write(&path).unwrap();
@@ -517,7 +572,7 @@ mod tests {
 
         // here we test if the cache releases
         // mmaps correctly.
-        let mmap_directory = MmapDirectory::create_from_tempdir().unwrap();
+        let mut mmap_directory = MmapDirectory::create_from_tempdir().unwrap();
         let num_paths = 10;
         let paths: Vec<PathBuf> = (0..num_paths)
             .map(|i| PathBuf::from(&*format!("file_{}", i)))
@@ -577,6 +632,27 @@ mod tests {
         assert_eq!(mmap_directory.get_cache_info().mmapped.len(), 0);
     }
 
+    #[test]
+    fn test_watch_wrapper() {
+        let counter: Arc<AtomicUsize> = Default::default();
+        let counter_clone = counter.clone();
+        let tmp_dir = tempfile::TempDir::new().unwrap();
+        let tmp_dirpath = tmp_dir.path().to_owned();
+        let mut watch_wrapper = WatcherWrapper::new(&tmp_dirpath).unwrap();
+        let tmp_file = tmp_dirpath.join(*META_FILEPATH);
+        let _handle = watch_wrapper.watch(Box::new(move || {
+            counter_clone.fetch_add(1, Ordering::SeqCst);
+        }));
+        let (sender, receiver) = crossbeam::channel::unbounded();
+        let _handle2 = watch_wrapper.watch(Box::new(move || {
+            let _ = sender.send(());
+        }));
+        assert_eq!(counter.load(Ordering::SeqCst), 0);
+        fs::write(&tmp_file, b"whateverwilldo").unwrap();
+        assert!(receiver.recv().is_ok());
+        assert!(counter.load(Ordering::SeqCst) >= 1);
+    }
+
     #[test]
     fn test_mmap_released() {
         let mmap_directory = MmapDirectory::create_from_tempdir().unwrap();
@@ -587,7 +663,7 @@ mod tests {
         {
             let index = Index::create(mmap_directory.clone(), schema).unwrap();
 
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             let mut log_merge_policy = LogMergePolicy::default();
             log_merge_policy.set_min_merge_size(3);
             index_writer.set_merge_policy(Box::new(log_merge_policy));

src/directory/mod.rs

@@ -9,13 +9,14 @@ mod mmap_directory;
 
 mod directory;
 mod directory_lock;
-mod file_slice;
-mod file_watcher;
 mod footer;
 mod managed_directory;
-mod owned_bytes;
 mod ram_directory;
+mod read_only_source;
+mod spilling_writer;
 mod watch_event_router;
+mod persistor;
+
 
 /// Errors specific to the directory module.
 pub mod error;
@@ -23,14 +24,12 @@ pub mod error;
 pub use self::directory::DirectoryLock;
 pub use self::directory::{Directory, DirectoryClone};
 pub use self::directory_lock::{Lock, INDEX_WRITER_LOCK, META_LOCK};
-pub(crate) use self::file_slice::{ArcBytes, WeakArcBytes};
-pub use self::file_slice::{FileHandle, FileSlice};
-pub use self::owned_bytes::OwnedBytes;
 pub use self::ram_directory::RAMDirectory;
+pub use self::read_only_source::ReadOnlySource;
+pub(crate) use self::spilling_writer::{SpillingResult, SpillingWriter};
 pub use self::watch_event_router::{WatchCallback, WatchCallbackList, WatchHandle};
 use std::io::{self, BufWriter, Write};
 use std::path::PathBuf;
-
 /// Outcome of the Garbage collection
 pub struct GarbageCollectionResult {
     /// List of files that were deleted in this cycle
@@ -84,10 +83,16 @@ impl<W: TerminatingWrite> TerminatingWrite for BufWriter<W> {
     }
 }
 
+impl TerminatingWrite for Vec<u8> {
+    fn terminate_ref(&mut self, _a: AntiCallToken) -> io::Result<()> {
+        Ok(())
+    }
+}
+
 #[cfg(test)]
 impl<'a> TerminatingWrite for &'a mut Vec<u8> {
     fn terminate_ref(&mut self, _a: AntiCallToken) -> io::Result<()> {
-        self.flush()
+        Ok(())
     }
 }
 

src/directory/owned_bytes.rs

@@ -1,290 +0,0 @@
-use crate::directory::FileHandle;
-use stable_deref_trait::StableDeref;
-use std::convert::TryInto;
-use std::mem;
-use std::ops::Deref;
-use std::sync::Arc;
-use std::{fmt, io};
-
-/// An OwnedBytes simply wraps an object that owns a slice of data and exposes
-/// this data as a static slice.
-///
-/// The backing object is required to be `StableDeref`.
-#[derive(Clone)]
-pub struct OwnedBytes {
-    data: &'static [u8],
-    box_stable_deref: Arc<dyn Deref<Target = [u8]> + Sync + Send>,
-}
-
-impl FileHandle for OwnedBytes {
-    fn read_bytes(&self, from: usize, to: usize) -> io::Result<OwnedBytes> {
-        Ok(self.slice(from, to))
-    }
-}
-
-impl OwnedBytes {
-    /// Creates an empty `OwnedBytes`.
-    pub fn empty() -> OwnedBytes {
-        OwnedBytes::new(&[][..])
-    }
-
-    /// Creates an `OwnedBytes` intance given a `StableDeref` object.
-    pub fn new<T: StableDeref + Deref<Target = [u8]> + 'static + Send + Sync>(
-        data_holder: T,
-    ) -> OwnedBytes {
-        let box_stable_deref = Arc::new(data_holder);
-        let bytes: &[u8] = box_stable_deref.as_ref();
-        let data = unsafe { mem::transmute::<_, &'static [u8]>(bytes.deref()) };
-        OwnedBytes {
-            box_stable_deref,
-            data,
-        }
-    }
-
-    /// creates a fileslice that is just a view over a slice of the data.
-    pub fn slice(&self, from: usize, to: usize) -> Self {
-        OwnedBytes {
-            data: &self.data[from..to],
-            box_stable_deref: self.box_stable_deref.clone(),
-        }
-    }
-
-    /// Returns the underlying slice of data.
-    /// `Deref` and `AsRef` are also available.
-    #[inline(always)]
-    pub fn as_slice(&self) -> &[u8] {
-        self.data
-    }
-
-    /// Returns the len of the slice.
-    #[inline(always)]
-    pub fn len(&self) -> usize {
-        self.data.len()
-    }
-
-    /// Splits the OwnedBytes into two OwnedBytes `(left, right)`.
-    ///
-    /// Left will hold `split_len` bytes.
-    ///
-    /// This operation is cheap and does not require to copy any memory.
-    /// On the other hand, both `left` and `right` retain a handle over
-    /// the entire slice of memory. In other words, the memory will only
-    /// be released when both left and right are dropped.
-    pub fn split(self, split_len: usize) -> (OwnedBytes, OwnedBytes) {
-        let right_box_stable_deref = self.box_stable_deref.clone();
-        let left = OwnedBytes {
-            data: &self.data[..split_len],
-            box_stable_deref: self.box_stable_deref,
-        };
-        let right = OwnedBytes {
-            data: &self.data[split_len..],
-            box_stable_deref: right_box_stable_deref,
-        };
-        (left, right)
-    }
-
-    /// Returns true iff this `OwnedBytes` is empty.
-    #[inline(always)]
-    pub fn is_empty(&self) -> bool {
-        self.as_slice().is_empty()
-    }
-
-    /// Drops the left most `advance_len` bytes.
-    ///
-    /// See also [.clip(clip_len: usize))](#method.clip).
-    #[inline(always)]
-    pub fn advance(&mut self, advance_len: usize) {
-        self.data = &self.data[advance_len..]
-    }
-
-    /// Reads an `u8` from the `OwnedBytes` and advance by one byte.
-    pub fn read_u8(&mut self) -> u8 {
-        assert!(!self.is_empty());
-
-        let byte = self.as_slice()[0];
-        self.advance(1);
-        byte
-    }
-
-    /// Reads an `u64` encoded as little-endian from the `OwnedBytes` and advance by 8 bytes.
-    pub fn read_u64(&mut self) -> u64 {
-        assert!(self.len() > 7);
-
-        let octlet: [u8; 8] = self.as_slice()[..8].try_into().unwrap();
-        self.advance(8);
-        u64::from_le_bytes(octlet)
-    }
-}
-
-impl fmt::Debug for OwnedBytes {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        // We truncate the bytes in order to make sure the debug string
-        // is not too long.
-        let bytes_truncated: &[u8] = if self.len() > 8 {
-            &self.as_slice()[..10]
-        } else {
-            self.as_slice()
-        };
-        write!(f, "OwnedBytes({:?}, len={})", bytes_truncated, self.len())
-    }
-}
-
-impl Deref for OwnedBytes {
-    type Target = [u8];
-
-    fn deref(&self) -> &Self::Target {
-        self.as_slice()
-    }
-}
-
-impl io::Read for OwnedBytes {
-    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        let read_len = {
-            let data = self.as_slice();
-            if data.len() >= buf.len() {
-                let buf_len = buf.len();
-                buf.copy_from_slice(&data[..buf_len]);
-                buf.len()
-            } else {
-                let data_len = data.len();
-                buf[..data_len].copy_from_slice(data);
-                data_len
-            }
-        };
-        self.advance(read_len);
-        Ok(read_len)
-    }
-    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
-        let read_len = {
-            let data = self.as_slice();
-            buf.extend(data);
-            data.len()
-        };
-        self.advance(read_len);
-        Ok(read_len)
-    }
-    fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
-        let read_len = self.read(buf)?;
-        if read_len != buf.len() {
-            return Err(io::Error::new(
-                io::ErrorKind::UnexpectedEof,
-                "failed to fill whole buffer",
-            ));
-        }
-        Ok(())
-    }
-}
-
-impl AsRef<[u8]> for OwnedBytes {
-    fn as_ref(&self) -> &[u8] {
-        self.as_slice()
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use std::io::{self, Read};
-
-    use super::OwnedBytes;
-
-    #[test]
-    fn test_owned_bytes_debug() {
-        let short_bytes = OwnedBytes::new(b"abcd".as_ref());
-        assert_eq!(
-            format!("{:?}", short_bytes),
-            "OwnedBytes([97, 98, 99, 100], len=4)"
-        );
-        let long_bytes = OwnedBytes::new(b"abcdefghijklmnopq".as_ref());
-        assert_eq!(
-            format!("{:?}", long_bytes),
-            "OwnedBytes([97, 98, 99, 100, 101, 102, 103, 104, 105, 106], len=17)"
-        );
-    }
-
-    #[test]
-    fn test_owned_bytes_read() -> io::Result<()> {
-        let mut bytes = OwnedBytes::new(b"abcdefghiklmnopqrstuvwxyz".as_ref());
-        {
-            let mut buf = [0u8; 5];
-            bytes.read_exact(&mut buf[..]).unwrap();
-            assert_eq!(&buf, b"abcde");
-            assert_eq!(bytes.as_slice(), b"fghiklmnopqrstuvwxyz")
-        }
-        {
-            let mut buf = [0u8; 2];
-            bytes.read_exact(&mut buf[..]).unwrap();
-            assert_eq!(&buf, b"fg");
-            assert_eq!(bytes.as_slice(), b"hiklmnopqrstuvwxyz")
-        }
-        Ok(())
-    }
-
-    #[test]
-    fn test_owned_bytes_read_right_at_the_end() -> io::Result<()> {
-        let mut bytes = OwnedBytes::new(b"abcde".as_ref());
-        let mut buf = [0u8; 5];
-        assert_eq!(bytes.read(&mut buf[..]).unwrap(), 5);
-        assert_eq!(&buf, b"abcde");
-        assert_eq!(bytes.as_slice(), b"");
-        assert_eq!(bytes.read(&mut buf[..]).unwrap(), 0);
-        assert_eq!(&buf, b"abcde");
-        Ok(())
-    }
-    #[test]
-    fn test_owned_bytes_read_incomplete() -> io::Result<()> {
-        let mut bytes = OwnedBytes::new(b"abcde".as_ref());
-        let mut buf = [0u8; 7];
-        assert_eq!(bytes.read(&mut buf[..]).unwrap(), 5);
-        assert_eq!(&buf[..5], b"abcde");
-        assert_eq!(bytes.read(&mut buf[..]).unwrap(), 0);
-        Ok(())
-    }
-
-    #[test]
-    fn test_owned_bytes_read_to_end() -> io::Result<()> {
-        let mut bytes = OwnedBytes::new(b"abcde".as_ref());
-        let mut buf = Vec::new();
-        bytes.read_to_end(&mut buf)?;
-        assert_eq!(buf.as_slice(), b"abcde".as_ref());
-        Ok(())
-    }
-
-    #[test]
-    fn test_owned_bytes_read_u8() -> io::Result<()> {
-        let mut bytes = OwnedBytes::new(b"\xFF".as_ref());
-        assert_eq!(bytes.read_u8(), 255);
-        assert_eq!(bytes.len(), 0);
-        Ok(())
-    }
-
-    #[test]
-    fn test_owned_bytes_read_u64() -> io::Result<()> {
-        let mut bytes = OwnedBytes::new(b"\0\xFF\xFF\xFF\xFF\xFF\xFF\xFF".as_ref());
-        assert_eq!(bytes.read_u64(), u64::MAX - 255);
-        assert_eq!(bytes.len(), 0);
-        Ok(())
-    }
-
-    #[test]
-    fn test_owned_bytes_split() {
-        let bytes = OwnedBytes::new(b"abcdefghi".as_ref());
-        let (left, right) = bytes.split(3);
-        assert_eq!(left.as_slice(), b"abc");
-        assert_eq!(right.as_slice(), b"defghi");
-    }
-
-    #[test]
-    fn test_owned_bytes_split_boundary() {
-        let bytes = OwnedBytes::new(b"abcdefghi".as_ref());
-        {
-            let (left, right) = bytes.clone().split(0);
-            assert_eq!(left.as_slice(), b"");
-            assert_eq!(right.as_slice(), b"abcdefghi");
-        }
-        {
-            let (left, right) = bytes.split(9);
-            assert_eq!(left.as_slice(), b"abcdefghi");
-            assert_eq!(right.as_slice(), b"");
-        }
-    }
-}

src/directory/persistor.rs

@@ -0,0 +1,38 @@
+use crate::indexer::{SegmentManager, ResourceManager, MergeOperationInventory};
+use std::thread::JoinHandle;
+use crate::{IndexWriterConfig, SegmentId};
+use std::collections::HashSet;
+
+pub(crate) struct Persistor {
+    memory_manager: ResourceManager,
+    thread_handle: JoinHandle<()>,
+}
+
+impl Persistor {
+    pub(crate) fn create_and_start(segment_manager: SegmentManager,
+                            memory_manager: ResourceManager,
+                            config: IndexWriterConfig) -> crate::Result<Persistor> {
+        let memory_manager_clone = memory_manager.clone();
+        let thread_handle = std::thread::Builder::new()
+            .name("persistor-thread".to_string())
+            .spawn(move || {
+                while let Ok(_) = memory_manager_clone.wait_until_in_range(config.persist_low..) {
+                    segment_manager.largest_segment_not_in_merge();
+                }
+            }).map_err(|_err| crate::TantivyError::ErrorInThread("Failed to start persistor thread.".to_string()))?;
+        Ok(Persistor {
+            memory_manager,
+            thread_handle
+        })
+    }
+
+    /// Stop the persisting thread.
+    ///
+    /// The memory manager will be terminated, which will unlock the thread from any waiting
+    /// position.
+    /// This method blocks for a short amount of tim until the persistor thread has terminated.
+    pub fn stop(self) {
+        self.memory_manager.terminate();
+        let _ = self.thread_handle.join();
+    }
+}

src/directory/ram_directory.rs

@@ -1,9 +1,9 @@
+use crate::core::META_FILEPATH;
 use crate::directory::error::{DeleteError, OpenReadError, OpenWriteError};
 use crate::directory::AntiCallToken;
 use crate::directory::WatchCallbackList;
-use crate::directory::{Directory, FileSlice, WatchCallback, WatchHandle};
+use crate::directory::{Directory, ReadOnlySource, WatchCallback, WatchHandle};
 use crate::directory::{TerminatingWrite, WritePtr};
-use crate::{common::HasLen, core::META_FILEPATH};
 use fail::fail_point;
 use std::collections::HashMap;
 use std::fmt;
@@ -11,8 +11,7 @@ use std::io::{self, BufWriter, Cursor, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
 use std::result;
 use std::sync::{Arc, RwLock};
-
+use crate::indexer::ResourceManager;
-use super::FileHandle;
 
 /// Writer associated with the `RAMDirectory`
 ///
@@ -82,17 +81,18 @@ impl TerminatingWrite for VecWriter {
 
 #[derive(Default)]
 struct InnerDirectory {
-    fs: HashMap<PathBuf, FileSlice>,
+    fs: HashMap<PathBuf, ReadOnlySource>,
     watch_router: WatchCallbackList,
+    memory_manager: ResourceManager,
 }
 
 impl InnerDirectory {
     fn write(&mut self, path: PathBuf, data: &[u8]) -> bool {
-        let data = FileSlice::from(data.to_vec());
+        let data = ReadOnlySource::new_with_allocation(Vec::from(data), &self.memory_manager);
         self.fs.insert(path, data).is_some()
     }
 
-    fn open_read(&self, path: &Path) -> Result<FileSlice, OpenReadError> {
+    fn open_read(&self, path: &Path) -> Result<ReadOnlySource, OpenReadError> {
         self.fs
             .get(path)
             .ok_or_else(|| OpenReadError::FileDoesNotExist(PathBuf::from(path)))
@@ -114,8 +114,8 @@ impl InnerDirectory {
         self.watch_router.subscribe(watch_handle)
     }
 
-    fn total_mem_usage(&self) -> usize {
+    fn total_mem_usage(&self) -> u64 {
-        self.fs.values().map(|f| f.len()).sum()
+        self.fs.values().map(|source| source.len() as u64).sum()
     }
 }
 
@@ -136,14 +136,30 @@ pub struct RAMDirectory {
 }
 
 impl RAMDirectory {
-    /// Constructor
+
+    /// Creates a new RAMDirectory.
+    ///
+    /// Check `.create_with_memory_manager(..)` if you want to associate an external memory
+    /// manager to your RAMDirectory.
     pub fn create() -> RAMDirectory {
-        Self::default()
+        RAMDirectory::default()
+    }
+
+    /// Constructor
+    pub fn create_with_memory_manager(memory_manager: ResourceManager) -> RAMDirectory {
+        let inner_directory = InnerDirectory {
+            fs: Default::default(),
+            watch_router: Default::default(),
+            memory_manager
+        };
+        RAMDirectory {
+            fs: Arc::new(RwLock::new(inner_directory))
+        }
     }
 
     /// Returns the sum of the size of the different files
     /// in the RAMDirectory.
-    pub fn total_mem_usage(&self) -> usize {
+    pub fn total_mem_usage(&self) -> u64 {
         self.fs.read().unwrap().total_mem_usage()
     }
 
@@ -153,11 +169,11 @@ impl RAMDirectory {
     /// written using the `atomic_write` api.
     ///
     /// If an error is encounterred, files may be persisted partially.
-    pub fn persist(&self, dest: &dyn Directory) -> crate::Result<()> {
+    pub fn persist(&self, dest: &mut dyn Directory) -> crate::Result<()> {
         let wlock = self.fs.write().unwrap();
-        for (path, file) in wlock.fs.iter() {
+        for (path, source) in wlock.fs.iter() {
             let mut dest_wrt = dest.open_write(path)?;
-            dest_wrt.write_all(file.read_bytes()?.as_slice())?;
+            dest_wrt.write_all(source.as_slice())?;
             dest_wrt.terminate()?;
         }
         Ok(())
@@ -165,37 +181,24 @@ impl RAMDirectory {
 }
 
 impl Directory for RAMDirectory {
-    fn get_file_handle(&self, path: &Path) -> Result<Box<dyn FileHandle>, OpenReadError> {
+    fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
-        let file_slice = self.open_read(path)?;
-        Ok(Box::new(file_slice))
-    }
-
-    fn open_read(&self, path: &Path) -> result::Result<FileSlice, OpenReadError> {
         self.fs.read().unwrap().open_read(path)
     }
 
     fn delete(&self, path: &Path) -> result::Result<(), DeleteError> {
         fail_point!("RAMDirectory::delete", |_| {
-            Err(DeleteError::IOError {
+            use crate::directory::error::IOError;
-                io_error: io::Error::from(io::ErrorKind::Other),
+            let io_error = IOError::from(io::Error::from(io::ErrorKind::Other));
-                filepath: path.to_path_buf(),
+            Err(DeleteError::from(io_error))
-            })
         });
         self.fs.write().unwrap().delete(path)
     }
 
-    fn exists(&self, path: &Path) -> Result<bool, OpenReadError> {
+    fn exists(&self, path: &Path) -> bool {
-        Ok(self
+        self.fs.read().unwrap().exists(path)
-            .fs
-            .read()
-            .map_err(|e| OpenReadError::IOError {
-                io_error: io::Error::new(io::ErrorKind::Other, e.to_string()),
-                filepath: path.to_path_buf(),
-            })?
-            .exists(path))
     }
 
-    fn open_write(&self, path: &Path) -> Result<WritePtr, OpenWriteError> {
+    fn open_write(&mut self, path: &Path) -> Result<WritePtr, OpenWriteError> {
         let mut fs = self.fs.write().unwrap();
         let path_buf = PathBuf::from(path);
         let vec_writer = VecWriter::new(path_buf.clone(), self.clone());
@@ -209,17 +212,10 @@ impl Directory for RAMDirectory {
     }
 
     fn atomic_read(&self, path: &Path) -> Result<Vec<u8>, OpenReadError> {
-        let bytes =
+        Ok(self.open_read(path)?.as_slice().to_owned())
-            self.open_read(path)?
-                .read_bytes()
-                .map_err(|io_error| OpenReadError::IOError {
-                    io_error,
-                    filepath: path.to_path_buf(),
-                })?;
-        Ok(bytes.as_slice().to_owned())
     }
 
-    fn atomic_write(&self, path: &Path, data: &[u8]) -> io::Result<()> {
+    fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
         fail_point!("RAMDirectory::atomic_write", |msg| Err(io::Error::new(
             io::ErrorKind::Other,
             msg.unwrap_or_else(|| "Undefined".to_string())
@@ -249,6 +245,9 @@ mod tests {
     use crate::Directory;
     use std::io::Write;
     use std::path::Path;
+    use crate::indexer::ResourceManager;
+    use crate::directory::TerminatingWrite;
+    use std::mem;
 
     #[test]
     fn test_persist() {
@@ -256,14 +255,69 @@ mod tests {
         let msg_seq: &'static [u8] = b"sequential is the way";
         let path_atomic: &'static Path = Path::new("atomic");
         let path_seq: &'static Path = Path::new("seq");
-        let directory = RAMDirectory::create();
+        let mut directory = RAMDirectory::create();
         assert!(directory.atomic_write(path_atomic, msg_atomic).is_ok());
         let mut wrt = directory.open_write(path_seq).unwrap();
         assert!(wrt.write_all(msg_seq).is_ok());
         assert!(wrt.flush().is_ok());
-        let directory_copy = RAMDirectory::create();
+        let mut directory_copy = RAMDirectory::create();
-        assert!(directory.persist(&directory_copy).is_ok());
+        assert!(directory.persist(&mut directory_copy).is_ok());
         assert_eq!(directory_copy.atomic_read(path_atomic).unwrap(), msg_atomic);
         assert_eq!(directory_copy.atomic_read(path_seq).unwrap(), msg_seq);
     }
+
+    #[test]
+    fn test_memory_manager_several_path() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcd").is_ok());
+        assert_eq!(memory_manager.total_amount(), 4u64);
+        assert!(ram_directory.atomic_write(Path::new("/toto"), b"abcde").is_ok());
+        assert_eq!(memory_manager.total_amount(), 9u64);
+    }
+
+    #[test]
+    fn test_memory_manager_override() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcde").is_ok());
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcdef").is_ok());
+        assert_eq!(memory_manager.total_amount(), 6u64);
+    }
+
+    #[test]
+    fn test_memory_manager_seq_wrt() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        let mut wrt = ram_directory.open_write(Path::new("/titi")).unwrap();
+        assert!(wrt.write_all(b"abcde").is_ok());
+        assert!(wrt.terminate().is_ok());
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcdef").is_ok());
+        assert_eq!(memory_manager.total_amount(), 6u64);
+    }
+
+    #[test]
+    fn test_release_on_drop() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        let mut wrt = ram_directory.open_write(Path::new("/titi")).unwrap();
+        assert!(wrt.write_all(b"abcde").is_ok());
+        assert!(wrt.terminate().is_ok());
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        let mut wrt2 = ram_directory.open_write(Path::new("/toto")).unwrap();
+        assert!(wrt2.write_all(b"abcdefghijkl").is_ok());
+        assert!(wrt2.terminate().is_ok());
+        assert_eq!(memory_manager.total_amount(), 17u64);
+        let source = ram_directory.open_read(Path::new("/titi")).unwrap();
+        let source_clone = source.clone();
+        assert_eq!(memory_manager.total_amount(), 17u64);
+        mem::drop(ram_directory);
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        mem::drop(source);
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        mem::drop(source_clone);
+        assert_eq!(memory_manager.total_amount(), 0u64);
+    }
 }

src/directory/read_only_source.rs

@@ -0,0 +1,157 @@
+use crate::common::HasLen;
+use stable_deref_trait::{CloneStableDeref, StableDeref};
+use std::ops::Deref;
+use std::sync::Arc;
+use crate::indexer::{Allocation, ResourceManager};
+
+pub type BoxedData = Box<dyn Deref<Target = [u8]> + Send + Sync + 'static>;
+
+/// Read object that represents files in tantivy.
+///
+/// These read objects are only in charge to deliver
+/// the data in the form of a constant read-only `&[u8]`.
+/// Whatever happens to the directory file, the data
+/// hold by this object should never be altered or destroyed.
+pub struct ReadOnlySource {
+    data: Arc<BoxedData>,
+    start: usize,
+    stop: usize,
+    allocation: Option<Arc<Allocation>>
+}
+
+unsafe impl StableDeref for ReadOnlySource {}
+unsafe impl CloneStableDeref for ReadOnlySource {}
+
+impl Deref for ReadOnlySource {
+    type Target = [u8];
+
+    fn deref(&self) -> &[u8] {
+        self.as_slice()
+    }
+}
+
+impl From<Arc<BoxedData>> for ReadOnlySource {
+    fn from(data: Arc<BoxedData>) -> Self {
+        let len = data.len();
+        ReadOnlySource {
+            data,
+            start: 0,
+            stop: len,
+            allocation: None
+        }
+    }
+}
+
+impl ReadOnlySource {
+
+    pub(crate) fn new<D>(data: D) -> ReadOnlySource
+    where
+        D: Deref<Target = [u8]> + Send + Sync + 'static,
+    {
+        let len = data.len();
+        ReadOnlySource {
+            data: Arc::new(Box::new(data)),
+            start: 0,
+            stop: len,
+            allocation: None
+        }
+    }
+
+    pub(crate) fn new_with_allocation<D>(data: D, memory_manager: &ResourceManager) -> ReadOnlySource
+        where
+            D: Deref<Target = [u8]> + Send + Sync + 'static,
+    {
+        let len = data.len();
+        ReadOnlySource {
+            data: Arc::new(Box::new(data)),
+            start: 0,
+            stop: len,
+            allocation: Some(Arc::new(memory_manager.allocate(len as u64)))
+        }
+    }
+
+
+    /// Creates an empty ReadOnlySource
+    pub fn empty() -> ReadOnlySource {
+        ReadOnlySource::new(&[][..])
+    }
+
+    /// Returns the data underlying the ReadOnlySource object.
+    pub fn as_slice(&self) -> &[u8] {
+        &self.data[self.start..self.stop]
+    }
+
+    /// Splits into 2 `ReadOnlySource`, at the offset given
+    /// as an argument.
+    pub fn split(self, addr: usize) -> (ReadOnlySource, ReadOnlySource) {
+        let left = self.slice(0, addr);
+        let right = self.slice_from(addr);
+        (left, right)
+    }
+
+    /// Splits into 2 `ReadOnlySource`, at the offset `end - right_len`.
+    pub fn split_from_end(self, right_len: usize) -> (ReadOnlySource, ReadOnlySource) {
+        let left_len = self.len() - right_len;
+        self.split(left_len)
+    }
+
+    /// Creates a ReadOnlySource that is just a
+    /// view over a slice of the data.
+    ///
+    /// Keep in mind that any living slice extends
+    /// the lifetime of the original ReadOnlySource,
+    ///
+    /// For instance, if `ReadOnlySource` wraps 500MB
+    /// worth of data in anonymous memory, and only a
+    /// 1KB slice is remaining, the whole `500MBs`
+    /// are retained in memory.
+    pub fn slice(&self, start: usize, stop: usize) -> ReadOnlySource {
+        assert!(
+            start <= stop,
+            "Requested negative slice [{}..{}]",
+            start,
+            stop
+        );
+        assert!(stop <= self.len());
+        ReadOnlySource {
+            data: self.data.clone(),
+            start: self.start + start,
+            stop: self.start + stop,
+            allocation: self.allocation.clone()
+        }
+    }
+
+    /// Like `.slice(...)` but enforcing only the `from`
+    /// boundary.
+    ///
+    /// Equivalent to `.slice(from_offset, self.len())`
+    pub fn slice_from(&self, from_offset: usize) -> ReadOnlySource {
+        self.slice(from_offset, self.len())
+    }
+
+    /// Like `.slice(...)` but enforcing only the `to`
+    /// boundary.
+    ///
+    /// Equivalent to `.slice(0, to_offset)`
+    pub fn slice_to(&self, to_offset: usize) -> ReadOnlySource {
+        self.slice(0, to_offset)
+    }
+}
+
+impl HasLen for ReadOnlySource {
+    fn len(&self) -> usize {
+        self.stop - self.start
+    }
+}
+
+impl Clone for ReadOnlySource {
+    fn clone(&self) -> Self {
+        self.slice_from(0)
+    }
+}
+
+impl From<Vec<u8>> for ReadOnlySource {
+    fn from(data: Vec<u8>) -> ReadOnlySource {
+        ReadOnlySource::new(data)
+    }
+}

src/directory/spilling_writer.rs

@@ -0,0 +1,186 @@
+use crate::common::MutableEnum;
+use crate::directory::{TerminatingWrite, WritePtr};
+use std::io::{self, Write};
+
+/// Represents the state of the `SpillingWriter`.
+enum SpillingState {
+    Buffer {
+        buffer: Vec<u8>,
+        capacity: usize,
+        write_factory: Box<dyn FnOnce() -> io::Result<WritePtr>>,
+    },
+    Spilled(WritePtr),
+}
+
+impl SpillingState {
+    fn new(
+        limit: usize,
+        write_factory: Box<dyn FnOnce() -> io::Result<WritePtr>>,
+    ) -> SpillingState {
+        SpillingState::Buffer {
+            buffer: Vec::with_capacity(limit),
+            capacity: limit,
+            write_factory,
+        }
+    }
+
+    // Change the state in such a way that it is ready to accept
+    // `extra_capacity` bytes.
+    //
+    fn reserve(self, extra_capacity: usize) -> io::Result<SpillingState> {
+        match self {
+            SpillingState::Buffer {
+                buffer,
+                capacity,
+                write_factory,
+            } => {
+                if capacity >= extra_capacity {
+                    Ok(SpillingState::Buffer {
+                        buffer,
+                        capacity: capacity - extra_capacity,
+                        write_factory,
+                    })
+                } else {
+                    let mut wrt = write_factory()?;
+                    wrt.write_all(&buffer[..])?;
+                    Ok(SpillingState::Spilled(wrt))
+                }
+            }
+            SpillingState::Spilled(wrt) => Ok(SpillingState::Spilled(wrt)),
+        }
+    }
+}
+
+/// The `SpillingWriter` is a writer that start by writing in a
+/// buffer.
+///
+/// Once a memory limit is reached, the spilling writer will
+/// call a given `WritePtr` factory and start spilling into it.
+///
+/// Spilling here includes:
+/// - writing all of the data that were written in the in-memory buffer so far
+/// - writing subsequent data as well.
+///
+/// Once entering "spilling" mode, the `SpillingWriter` stays in this mode.
+pub struct SpillingWriter {
+    state: MutableEnum<SpillingState>,
+}
+
+impl SpillingWriter {
+    //// Creates a new `Spilling Writer`.
+    pub fn new(
+        limit: usize,
+        write_factory: Box<dyn FnOnce() -> io::Result<WritePtr>>,
+    ) -> SpillingWriter {
+        let state = SpillingState::new(limit, write_factory);
+        SpillingWriter {
+            state: MutableEnum::wrap(state),
+        }
+    }
+
+    /// Finalizes the `SpillingWriter`.
+    ///
+    /// The `SpillingResult` object is an enum specific
+    /// to whether the `SpillingWriter` reached the spilling limit
+    /// (In that case, the buffer is returned).
+    ///
+    /// If the writer reached the spilling mode, the underlying `WritePtr`
+    /// is terminated and SpillingResult::Spilled is returned.
+    pub fn finalize(self) -> io::Result<SpillingResult> {
+        match self.state.into() {
+            SpillingState::Spilled(wrt) => {
+                wrt.terminate()?;
+                Ok(SpillingResult::Spilled)
+            }
+            SpillingState::Buffer { buffer, .. } => Ok(SpillingResult::Buffer(buffer)),
+        }
+    }
+}
+
+/// enum used as the result of `.finalize()`.
+pub enum SpillingResult {
+    Spilled,
+    Buffer(Vec<u8>),
+}
+
+impl io::Write for SpillingWriter {
+    fn write(&mut self, payload: &[u8]) -> io::Result<usize> {
+        self.write_all(payload)?;
+        Ok(payload.len())
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        if let SpillingState::Spilled(wrt) = &mut *self.state {
+            wrt.flush()?;
+        }
+        Ok(())
+    }
+
+    fn write_all(&mut self, payload: &[u8]) -> io::Result<()> {
+        self.state.map_mutate(|mut state| {
+            state = state.reserve(payload.len())?;
+            match &mut state {
+                SpillingState::Buffer { buffer, .. } => {
+                    buffer.extend_from_slice(payload);
+                }
+                SpillingState::Spilled(wrt) => {
+                    wrt.write_all(payload)?;
+                }
+            }
+            Ok(state)
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::SpillingWriter;
+    use crate::directory::spilling_writer::SpillingResult;
+    use crate::directory::RAMDirectory;
+    use crate::Directory;
+    use std::io::{self, Write};
+    use std::path::Path;
+
+    #[test]
+    fn test_no_spilling() {
+        let ram_directory = RAMDirectory::create();
+        let mut ram_directory_clone = ram_directory.clone();
+        let path = Path::new("test");
+        let write_factory = Box::new(move || {
+            ram_directory_clone
+                .open_write(path)
+                .map_err(|err| io::Error::new(io::ErrorKind::Other, err))
+        });
+        let mut spilling_wrt = SpillingWriter::new(10, write_factory);
+        assert!(spilling_wrt.write_all(b"abcd").is_ok());
+        if let SpillingResult::Buffer(buf) = spilling_wrt.finalize().unwrap() {
+            assert_eq!(buf, b"abcd")
+        } else {
+            panic!("spill writer should not have spilled");
+        }
+        assert!(!ram_directory.exists(path));
+    }
+
+    #[test]
+    fn test_spilling() {
+        let ram_directory = RAMDirectory::create();
+        let mut ram_directory_clone = ram_directory.clone();
+        let path = Path::new("test");
+        let write_factory = Box::new(move || {
+            ram_directory_clone
+                .open_write(path)
+                .map_err(|err| io::Error::new(io::ErrorKind::Other, err))
+        });
+        let mut spilling_wrt = SpillingWriter::new(10, write_factory);
+        assert!(spilling_wrt.write_all(b"abcd").is_ok());
+        assert!(spilling_wrt.write_all(b"efghijklmnop").is_ok());
+        if let SpillingResult::Spilled = spilling_wrt.finalize().unwrap() {
+        } else {
+            panic!("spill writer should have spilled");
+        }
+        assert_eq!(
+            ram_directory.atomic_read(path).unwrap(),
+            b"abcdefghijklmnop"
+        );
+    }
+}

src/directory/tests.rs

@@ -20,47 +20,45 @@ mod mmap_directory_tests {
     }
 
     #[test]
-    fn test_simple() -> crate::Result<()> {
+    fn test_simple() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_simple(&directory)
+        super::test_simple(&mut directory);
     }
 
     #[test]
     fn test_write_create_the_file() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_write_create_the_file(&directory);
+        super::test_write_create_the_file(&mut directory);
     }
 
     #[test]
-    fn test_rewrite_forbidden() -> crate::Result<()> {
+    fn test_rewrite_forbidden() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_rewrite_forbidden(&directory)?;
+        super::test_rewrite_forbidden(&mut directory);
-        Ok(())
     }
 
     #[test]
-    fn test_directory_delete() -> crate::Result<()> {
+    fn test_directory_delete() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_directory_delete(&directory)?;
+        super::test_directory_delete(&mut directory);
-        Ok(())
     }
 
     #[test]
     fn test_lock_non_blocking() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_lock_non_blocking(&directory);
+        super::test_lock_non_blocking(&mut directory);
     }
 
     #[test]
     fn test_lock_blocking() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_lock_blocking(&directory);
+        super::test_lock_blocking(&mut directory);
     }
 
     #[test]
     fn test_watch() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_watch(&directory);
+        super::test_watch(&mut directory);
     }
 }
 
@@ -74,47 +72,45 @@ mod ram_directory_tests {
     }
 
     #[test]
-    fn test_simple() -> crate::Result<()> {
+    fn test_simple() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_simple(&directory)
+        super::test_simple(&mut directory);
     }
 
     #[test]
     fn test_write_create_the_file() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_write_create_the_file(&directory);
+        super::test_write_create_the_file(&mut directory);
     }
 
     #[test]
-    fn test_rewrite_forbidden() -> crate::Result<()> {
+    fn test_rewrite_forbidden() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_rewrite_forbidden(&directory)?;
+        super::test_rewrite_forbidden(&mut directory);
-        Ok(())
     }
 
     #[test]
-    fn test_directory_delete() -> crate::Result<()> {
+    fn test_directory_delete() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_directory_delete(&directory)?;
+        super::test_directory_delete(&mut directory);
-        Ok(())
     }
 
     #[test]
     fn test_lock_non_blocking() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_lock_non_blocking(&directory);
+        super::test_lock_non_blocking(&mut directory);
     }
 
     #[test]
     fn test_lock_blocking() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_lock_blocking(&directory);
+        super::test_lock_blocking(&mut directory);
     }
 
     #[test]
     fn test_watch() {
-        let directory = make_directory();
+        let mut directory = make_directory();
-        super::test_watch(&directory);
+        super::test_watch(&mut directory);
     }
 }
 
@@ -122,61 +118,68 @@ mod ram_directory_tests {
 #[should_panic]
 fn ram_directory_panics_if_flush_forgotten() {
     let test_path: &'static Path = Path::new("some_path_for_test");
-    let ram_directory = RAMDirectory::create();
+    let mut ram_directory = RAMDirectory::create();
     let mut write_file = ram_directory.open_write(test_path).unwrap();
     assert!(write_file.write_all(&[4]).is_ok());
 }
 
-fn test_simple(directory: &dyn Directory) -> crate::Result<()> {
+fn test_simple(directory: &mut dyn Directory) {
     let test_path: &'static Path = Path::new("some_path_for_test");
-    let mut write_file = directory.open_write(test_path)?;
+    {
-    assert!(directory.exists(test_path).unwrap());
+        let mut write_file = directory.open_write(test_path).unwrap();
-    write_file.write_all(&[4])?;
+        assert!(directory.exists(test_path));
-    write_file.write_all(&[3])?;
+        write_file.write_all(&[4]).unwrap();
-    write_file.write_all(&[7, 3, 5])?;
+        write_file.write_all(&[3]).unwrap();
-    write_file.flush()?;
+        write_file.write_all(&[7, 3, 5]).unwrap();
-    let read_file = directory.open_read(test_path)?.read_bytes()?;
+        write_file.flush().unwrap();
-    assert_eq!(read_file.as_slice(), &[4u8, 3u8, 7u8, 3u8, 5u8]);
+    }
-    mem::drop(read_file);
+    {
+        let read_file = directory.open_read(test_path).unwrap();
+        let data: &[u8] = &*read_file;
+        assert_eq!(data, &[4u8, 3u8, 7u8, 3u8, 5u8]);
+    }
     assert!(directory.delete(test_path).is_ok());
-    assert!(!directory.exists(test_path).unwrap());
+    assert!(!directory.exists(test_path));
-    Ok(())
 }
 
-fn test_rewrite_forbidden(directory: &dyn Directory) -> crate::Result<()> {
+fn test_rewrite_forbidden(directory: &mut dyn Directory) {
     let test_path: &'static Path = Path::new("some_path_for_test");
-    directory.open_write(test_path)?;
+    {
-    assert!(directory.exists(test_path).unwrap());
+        directory.open_write(test_path).unwrap();
-    assert!(directory.open_write(test_path).is_err());
+        assert!(directory.exists(test_path));
+    }
+    {
+        assert!(directory.open_write(test_path).is_err());
+    }
     assert!(directory.delete(test_path).is_ok());
-    Ok(())
 }
 
-fn test_write_create_the_file(directory: &dyn Directory) {
+fn test_write_create_the_file(directory: &mut dyn Directory) {
     let test_path: &'static Path = Path::new("some_path_for_test");
     {
         assert!(directory.open_read(test_path).is_err());
         let _w = directory.open_write(test_path).unwrap();
-        assert!(directory.exists(test_path).unwrap());
+        assert!(directory.exists(test_path));
         assert!(directory.open_read(test_path).is_ok());
         assert!(directory.delete(test_path).is_ok());
     }
 }
 
-fn test_directory_delete(directory: &dyn Directory) -> crate::Result<()> {
+fn test_directory_delete(directory: &mut dyn Directory) {
     let test_path: &'static Path = Path::new("some_path_for_test");
     assert!(directory.open_read(test_path).is_err());
-    let mut write_file = directory.open_write(&test_path)?;
+    let mut write_file = directory.open_write(&test_path).unwrap();
-    write_file.write_all(&[1, 2, 3, 4])?;
+    write_file.write_all(&[1, 2, 3, 4]).unwrap();
-    write_file.flush()?;
+    write_file.flush().unwrap();
     {
-        let read_handle = directory.open_read(&test_path)?.read_bytes()?;
+        let read_handle = directory.open_read(&test_path).unwrap();
-        assert_eq!(read_handle.as_slice(), &[1u8, 2u8, 3u8, 4u8]);
+        assert_eq!(&*read_handle, &[1u8, 2u8, 3u8, 4u8]);
         // Mapped files can't be deleted on Windows
         if !cfg!(windows) {
             assert!(directory.delete(&test_path).is_ok());
-            assert_eq!(read_handle.as_slice(), &[1u8, 2u8, 3u8, 4u8]);
+            assert_eq!(&*read_handle, &[1u8, 2u8, 3u8, 4u8]);
         }
+
         assert!(directory.delete(Path::new("SomeOtherPath")).is_err());
     }
 
@@ -186,40 +189,44 @@ fn test_directory_delete(directory: &dyn Directory) -> crate::Result<()> {
 
     assert!(directory.open_read(&test_path).is_err());
     assert!(directory.delete(&test_path).is_err());
-    Ok(())
 }
 
-fn test_watch(directory: &dyn Directory) {
+fn test_watch(directory: &mut dyn Directory) {
+    let num_progress: Arc<AtomicUsize> = Default::default();
     let counter: Arc<AtomicUsize> = Default::default();
-    let (tx, rx) = crossbeam::channel::unbounded();
+    let counter_clone = counter.clone();
-    let timeout = Duration::from_millis(500);
+    let (sender, receiver) = crossbeam::channel::unbounded();
-
+    let watch_callback = Box::new(move || {
-    let handle = directory
+        counter_clone.fetch_add(1, SeqCst);
-        .watch(WatchCallback::new(move || {
+    });
-            let val = counter.fetch_add(1, SeqCst);
+    // This callback is used to synchronize watching in our unit test.
-            tx.send(val + 1).unwrap();
+    // We bind it to a variable because the callback is removed when that
+    // handle is dropped.
+    let watch_handle = directory.watch(watch_callback).unwrap();
+    let _progress_listener = directory
+        .watch(Box::new(move || {
+            let val = num_progress.fetch_add(1, SeqCst);
+            let _ = sender.send(val);
         }))
         .unwrap();
 
+    for i in 0..10 {
+        assert_eq!(i, counter.load(SeqCst));
+        assert!(directory
+            .atomic_write(Path::new("meta.json"), b"random_test_data_2")
+            .is_ok());
+        assert_eq!(receiver.recv_timeout(Duration::from_millis(500)), Ok(i));
+        assert_eq!(i + 1, counter.load(SeqCst));
+    }
+    mem::drop(watch_handle);
     assert!(directory
-        .atomic_write(Path::new("meta.json"), b"foo")
+        .atomic_write(Path::new("meta.json"), b"random_test_data")
         .is_ok());
-    assert_eq!(rx.recv_timeout(timeout), Ok(1));
+    assert!(receiver.recv_timeout(Duration::from_millis(500)).is_ok());
-
+    assert_eq!(10, counter.load(SeqCst));
-    assert!(directory
-        .atomic_write(Path::new("meta.json"), b"bar")
-        .is_ok());
-    assert_eq!(rx.recv_timeout(timeout), Ok(2));
-
-    mem::drop(handle);
-
-    assert!(directory
-        .atomic_write(Path::new("meta.json"), b"qux")
-        .is_ok());
-    assert!(rx.recv_timeout(timeout).is_err());
 }
 
-fn test_lock_non_blocking(directory: &dyn Directory) {
+fn test_lock_non_blocking(directory: &mut dyn Directory) {
     {
         let lock_a_res = directory.acquire_lock(&Lock {
             filepath: PathBuf::from("a.lock"),
@@ -244,7 +251,7 @@ fn test_lock_non_blocking(directory: &dyn Directory) {
     assert!(lock_a_res.is_ok());
 }
 
-fn test_lock_blocking(directory: &dyn Directory) {
+fn test_lock_blocking(directory: &mut dyn Directory) {
     let lock_a_res = directory.acquire_lock(&Lock {
         filepath: PathBuf::from("a.lock"),
         is_blocking: true,

src/directory/watch_event_router.rs

@@ -4,20 +4,8 @@ use std::sync::Arc;
 use std::sync::RwLock;
 use std::sync::Weak;
 
-/// Cloneable wrapper for callbacks registered when watching files of a `Directory`.
+/// Type alias for callbacks registered when watching files of a `Directory`.
-#[derive(Clone)]
+pub type WatchCallback = Box<dyn Fn() -> () + Sync + Send>;
-pub struct WatchCallback(Arc<dyn Fn() + Sync + Send>);
-
-impl WatchCallback {
-    /// Wraps a `Fn()` to create a WatchCallback.
-    pub fn new<F: Fn() + Sync + Send + 'static>(op: F) -> Self {
-        WatchCallback(Arc::new(op))
-    }
-
-    fn call(&self) {
-        self.0()
-    }
-}
 
 /// Helper struct to implement the watch method in `Directory` implementations.
 ///
@@ -41,17 +29,10 @@ impl WatchHandle {
     pub fn new(watch_callback: Arc<WatchCallback>) -> WatchHandle {
         WatchHandle(watch_callback)
     }
-
-    /// Returns an empty watch handle.
-    ///
-    /// This function is only useful when implementing a readonly directory.
-    pub fn empty() -> WatchHandle {
-        WatchHandle::new(Arc::new(WatchCallback::new(|| {})))
-    }
 }
 
 impl WatchCallbackList {
-    /// Subscribes a new callback and returns a handle that controls the lifetime of the callback.
+    /// Suscribes a new callback and returns a handle that controls the lifetime of the callback.
     pub fn subscribe(&self, watch_callback: WatchCallback) -> WatchHandle {
         let watch_callback_arc = Arc::new(watch_callback);
         let watch_callback_weak = Arc::downgrade(&watch_callback_arc);
@@ -59,13 +40,13 @@ impl WatchCallbackList {
         WatchHandle::new(watch_callback_arc)
     }
 
-    fn list_callback(&self) -> Vec<WatchCallback> {
+    fn list_callback(&self) -> Vec<Arc<WatchCallback>> {
-        let mut callbacks: Vec<WatchCallback> = vec![];
+        let mut callbacks = vec![];
         let mut router_wlock = self.router.write().unwrap();
         let mut i = 0;
         while i < router_wlock.len() {
             if let Some(watch) = router_wlock[i].upgrade() {
-                callbacks.push(watch.as_ref().clone());
+                callbacks.push(watch);
                 i += 1;
             } else {
                 router_wlock.swap_remove(i);
@@ -87,7 +68,7 @@ impl WatchCallbackList {
             .name("watch-callbacks".to_string())
             .spawn(move || {
                 for callback in callbacks {
-                    callback.call();
+                    callback();
                 }
                 let _ = sender.send(());
             });
@@ -103,7 +84,7 @@ impl WatchCallbackList {
 
 #[cfg(test)]
 mod tests {
-    use crate::directory::{WatchCallback, WatchCallbackList};
+    use crate::directory::WatchCallbackList;
     use futures::executor::block_on;
     use std::mem;
     use std::sync::atomic::{AtomicUsize, Ordering};
@@ -114,7 +95,7 @@ mod tests {
         let watch_event_router = WatchCallbackList::default();
         let counter: Arc<AtomicUsize> = Default::default();
         let counter_clone = counter.clone();
-        let inc_callback = WatchCallback::new(move || {
+        let inc_callback = Box::new(move || {
             counter_clone.fetch_add(1, Ordering::SeqCst);
         });
         block_on(watch_event_router.broadcast());
@@ -142,7 +123,7 @@ mod tests {
         let counter: Arc<AtomicUsize> = Default::default();
         let inc_callback = |inc: usize| {
             let counter_clone = counter.clone();
-            WatchCallback::new(move || {
+            Box::new(move || {
                 counter_clone.fetch_add(inc, Ordering::SeqCst);
             })
         };
@@ -170,7 +151,7 @@ mod tests {
         let watch_event_router = WatchCallbackList::default();
         let counter: Arc<AtomicUsize> = Default::default();
         let counter_clone = counter.clone();
-        let inc_callback = WatchCallback::new(move || {
+        let inc_callback = Box::new(move || {
             counter_clone.fetch_add(1, Ordering::SeqCst);
         });
         let handle_a = watch_event_router.subscribe(inc_callback);

src/docset.rs

@@ -1,48 +1,58 @@
+use crate::common::BitSet;
 use crate::fastfield::DeleteBitSet;
 use crate::DocId;
 use std::borrow::Borrow;
 use std::borrow::BorrowMut;
+use std::cmp::Ordering;
 
-/// Sentinel value returned when a DocSet has been entirely consumed.
+/// Expresses the outcome of a call to `DocSet`'s `.skip_next(...)`.
-///
+#[derive(PartialEq, Eq, Debug)]
-/// This is not u32::MAX as one would have expected, due to the lack of SSE2 instructions
+pub enum SkipResult {
-/// to compare [u32; 4].
+    /// target was in the docset
-pub const TERMINATED: DocId = std::i32::MAX as u32;
+    Reached,
+    /// target was not in the docset, skipping stopped as a greater element was found
+    OverStep,
+    /// the docset was entirely consumed without finding the target, nor any
+    /// element greater than the target.
+    End,
+}
 
 /// Represents an iterable set of sorted doc ids.
-pub trait DocSet: Send {
+pub trait DocSet {
     /// Goes to the next element.
-    ///
+    /// `.advance(...)` needs to be called a first time to point to the correct
-    /// The DocId of the next element is returned.
+    /// element.
-    /// In other words we should always have :
+    fn advance(&mut self) -> bool;
-    /// ```ignore
-    /// let doc = docset.advance();
-    /// assert_eq!(doc, docset.doc());
-    /// ```
-    ///
-    /// If we reached the end of the DocSet, TERMINATED should be returned.
-    ///
-    /// Calling `.advance()` on a terminated DocSet should be supported, and TERMINATED should
-    /// be returned.
-    /// TODO Test existing docsets.
-    fn advance(&mut self) -> DocId;
 
-    /// Advances the DocSet forward until reaching the target, or going to the
+    /// After skipping, position the iterator in such a way that `.doc()`
-    /// lowest DocId greater than the target.
+    /// will return a value greater than or equal to target.
     ///
-    /// If the end of the DocSet is reached, TERMINATED is returned.
+    /// SkipResult expresses whether the `target value` was reached, overstepped,
+    /// or if the `DocSet` was entirely consumed without finding any value
+    /// greater or equal to the `target`.
     ///
-    /// Calling `.seek(target)` on a terminated DocSet is legal. Implementation
+    /// WARNING: Calling skip always advances the docset.
-    /// of DocSet should support it.
+    /// More specifically, if the docset is already positionned on the target
+    /// skipping will advance to the next position and return SkipResult::Overstep.
     ///
-    /// Calling `seek(TERMINATED)` is also legal and is the normal way to consume a DocSet.
+    /// If `.skip_next()` oversteps, then the docset must be positionned correctly
-    fn seek(&mut self, target: DocId) -> DocId {
+    /// on an existing document. In other words, `.doc()` should return the first document
-        let mut doc = self.doc();
+    /// greater than `DocId`.
-        debug_assert!(doc <= target);
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
-        while doc < target {
+        if !self.advance() {
-            doc = self.advance();
+            return SkipResult::End;
+        }
+        loop {
+            match self.doc().cmp(&target) {
+                Ordering::Less => {
+                    if !self.advance() {
+                        return SkipResult::End;
+                    }
+                }
+                Ordering::Equal => return SkipResult::Reached,
+                Ordering::Greater => return SkipResult::OverStep,
+            }
         }
-        doc
     }
 
     /// Fills a given mutable buffer with the next doc ids from the
@@ -61,38 +71,38 @@ pub trait DocSet: Send {
     /// use case where batching. The normal way to
     /// go through the `DocId`'s is to call `.advance()`.
     fn fill_buffer(&mut self, buffer: &mut [DocId]) -> usize {
-        if self.doc() == TERMINATED {
-            return 0;
-        }
         for (i, buffer_val) in buffer.iter_mut().enumerate() {
-            *buffer_val = self.doc();
+            if self.advance() {
-            if self.advance() == TERMINATED {
+                *buffer_val = self.doc();
-                return i + 1;
+            } else {
+                return i;
             }
         }
         buffer.len()
     }
 
     /// Returns the current document
-    /// Right after creating a new DocSet, the docset points to the first document.
-    ///
-    /// If the DocSet is empty, .doc() should return `TERMINATED`.
     fn doc(&self) -> DocId;
 
     /// Returns a best-effort hint of the
     /// length of the docset.
     fn size_hint(&self) -> u32;
 
+    /// Appends all docs to a `bitset`.
+    fn append_to_bitset(&mut self, bitset: &mut BitSet) {
+        while self.advance() {
+            bitset.insert(self.doc());
+        }
+    }
+
     /// Returns the number documents matching.
     /// Calling this method consumes the `DocSet`.
     fn count(&mut self, delete_bitset: &DeleteBitSet) -> u32 {
         let mut count = 0u32;
-        let mut doc = self.doc();
+        while self.advance() {
-        while doc != TERMINATED {
+            if !delete_bitset.is_deleted(self.doc()) {
-            if !delete_bitset.is_deleted(doc) {
                 count += 1u32;
             }
-            doc = self.advance();
         }
         count
     }
@@ -104,50 +114,22 @@ pub trait DocSet: Send {
     /// given by `count()`.
     fn count_including_deleted(&mut self) -> u32 {
         let mut count = 0u32;
-        let mut doc = self.doc();
+        while self.advance() {
-        while doc != TERMINATED {
             count += 1u32;
-            doc = self.advance();
         }
         count
     }
 }
 
-impl<'a> DocSet for &'a mut dyn DocSet {
-    fn advance(&mut self) -> u32 {
-        (**self).advance()
-    }
-
-    fn seek(&mut self, target: DocId) -> DocId {
-        (**self).seek(target)
-    }
-
-    fn doc(&self) -> u32 {
-        (**self).doc()
-    }
-
-    fn size_hint(&self) -> u32 {
-        (**self).size_hint()
-    }
-
-    fn count(&mut self, delete_bitset: &DeleteBitSet) -> u32 {
-        (**self).count(delete_bitset)
-    }
-
-    fn count_including_deleted(&mut self) -> u32 {
-        (**self).count_including_deleted()
-    }
-}
-
 impl<TDocSet: DocSet + ?Sized> DocSet for Box<TDocSet> {
-    fn advance(&mut self) -> DocId {
+    fn advance(&mut self) -> bool {
         let unboxed: &mut TDocSet = self.borrow_mut();
         unboxed.advance()
     }
 
-    fn seek(&mut self, target: DocId) -> DocId {
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
         let unboxed: &mut TDocSet = self.borrow_mut();
-        unboxed.seek(target)
+        unboxed.skip_next(target)
     }
 
     fn doc(&self) -> DocId {
@@ -169,4 +151,9 @@ impl<TDocSet: DocSet + ?Sized> DocSet for Box<TDocSet> {
         let unboxed: &mut TDocSet = self.borrow_mut();
         unboxed.count_including_deleted()
     }
+
+    fn append_to_bitset(&mut self, bitset: &mut BitSet) {
+        let unboxed: &mut TDocSet = self.borrow_mut();
+        unboxed.append_to_bitset(bitset);
+    }
 }

src/error.rs

@@ -2,27 +2,22 @@
 
 use std::io;
 
+use crate::directory::error::{IOError, OpenDirectoryError, OpenReadError, OpenWriteError};
 use crate::directory::error::{Incompatibility, LockError};
 use crate::fastfield::FastFieldNotAvailableError;
 use crate::query;
-use crate::{
+use crate::schema;
-    directory::error::{OpenDirectoryError, OpenReadError, OpenWriteError},
+use serde_json;
-    schema,
-};
 use std::fmt;
 use std::path::PathBuf;
 use std::sync::PoisonError;
 
-/// Represents a `DataCorruption` error.
-///
-/// When facing data corruption, tantivy  actually panic or return this error.
 pub struct DataCorruption {
     filepath: Option<PathBuf>,
     comment: String,
 }
 
 impl DataCorruption {
-    /// Creates a `DataCorruption` Error.
     pub fn new(filepath: PathBuf, comment: String) -> DataCorruption {
         DataCorruption {
             filepath: Some(filepath),
@@ -30,11 +25,10 @@ impl DataCorruption {
         }
     }
 
-    /// Creates a `DataCorruption` Error, when the filepath is irrelevant.
+    pub fn comment_only(comment: String) -> DataCorruption {
-    pub fn comment_only<TStr: ToString>(comment: TStr) -> DataCorruption {
         DataCorruption {
             filepath: None,
-            comment: comment.to_string(),
+            comment,
         }
     }
 }
@@ -50,47 +44,44 @@ impl fmt::Debug for DataCorruption {
     }
 }
 
-/// The library's error enum
+/// The library's failure based error enum
-#[derive(Debug, Error)]
+#[derive(Debug, Fail)]
 pub enum TantivyError {
-    /// Failed to open the directory.
+    /// Path does not exist.
-    #[error("Failed to open the directory: '{0:?}'")]
+    #[fail(display = "Path does not exist: '{:?}'", _0)]
-    OpenDirectoryError(#[from] OpenDirectoryError),
+    PathDoesNotExist(PathBuf),
-    /// Failed to open a file for read.
+    /// File already exists, this is a problem when we try to write into a new file.
-    #[error("Failed to open file for read: '{0:?}'")]
+    #[fail(display = "File already exists: '{:?}'", _0)]
-    OpenReadError(#[from] OpenReadError),
+    FileAlreadyExists(PathBuf),
-    /// Failed to open a file for write.
-    #[error("Failed to open file for write: '{0:?}'")]
-    OpenWriteError(#[from] OpenWriteError),
     /// Index already exists in this directory
-    #[error("Index already exists")]
+    #[fail(display = "Index already exists")]
     IndexAlreadyExists,
     /// Failed to acquire file lock
-    #[error("Failed to acquire Lockfile: {0:?}. {1:?}")]
+    #[fail(display = "Failed to acquire Lockfile: {:?}. {:?}", _0, _1)]
     LockFailure(LockError, Option<String>),
     /// IO Error.
-    #[error("An IO error occurred: '{0}'")]
+    #[fail(display = "An IO error occurred: '{}'", _0)]
-    IOError(#[from] io::Error),
+    IOError(#[cause] IOError),
     /// Data corruption.
-    #[error("Data corrupted: '{0:?}'")]
+    #[fail(display = "{:?}", _0)]
     DataCorruption(DataCorruption),
     /// A thread holding the locked panicked and poisoned the lock.
-    #[error("A thread holding the locked panicked and poisoned the lock")]
+    #[fail(display = "A thread holding the locked panicked and poisoned the lock")]
     Poisoned,
     /// Invalid argument was passed by the user.
-    #[error("An invalid argument was passed: '{0}'")]
+    #[fail(display = "An invalid argument was passed: '{}'", _0)]
     InvalidArgument(String),
     /// An Error happened in one of the thread.
-    #[error("An error occurred in a thread: '{0}'")]
+    #[fail(display = "An error occurred in a thread: '{}'", _0)]
     ErrorInThread(String),
     /// An Error appeared related to the schema.
-    #[error("Schema error: '{0}'")]
+    #[fail(display = "Schema error: '{}'", _0)]
     SchemaError(String),
     /// System error. (e.g.: We failed spawning a new thread)
-    #[error("System error.'{0}'")]
+    #[fail(display = "System error.'{}'", _0)]
     SystemError(String),
     /// Index incompatible with current version of tantivy
-    #[error("{0:?}")]
+    #[fail(display = "{:?}", _0)]
     IncompatibleIndex(Incompatibility),
 }
 
@@ -99,17 +90,31 @@ impl From<DataCorruption> for TantivyError {
         TantivyError::DataCorruption(data_corruption)
     }
 }
+
 impl From<FastFieldNotAvailableError> for TantivyError {
     fn from(fastfield_error: FastFieldNotAvailableError) -> TantivyError {
         TantivyError::SchemaError(format!("{}", fastfield_error))
     }
 }
+
 impl From<LockError> for TantivyError {
     fn from(lock_error: LockError) -> TantivyError {
         TantivyError::LockFailure(lock_error, None)
     }
 }
 
+impl From<IOError> for TantivyError {
+    fn from(io_error: IOError) -> TantivyError {
+        TantivyError::IOError(io_error)
+    }
+}
+
+impl From<io::Error> for TantivyError {
+    fn from(io_error: io::Error) -> TantivyError {
+        TantivyError::IOError(io_error.into())
+    }
+}
+
 impl From<query::QueryParserError> for TantivyError {
     fn from(parsing_error: query::QueryParserError) -> TantivyError {
         TantivyError::InvalidArgument(format!("Query is invalid. {:?}", parsing_error))
@@ -122,9 +127,15 @@ impl<Guard> From<PoisonError<Guard>> for TantivyError {
     }
 }
 
-impl From<chrono::ParseError> for TantivyError {
+impl From<OpenReadError> for TantivyError {
-    fn from(err: chrono::ParseError) -> TantivyError {
+    fn from(error: OpenReadError) -> TantivyError {
-        TantivyError::InvalidArgument(err.to_string())
+        match error {
+            OpenReadError::FileDoesNotExist(filepath) => TantivyError::PathDoesNotExist(filepath),
+            OpenReadError::IOError(io_error) => TantivyError::IOError(io_error),
+            OpenReadError::IncompatibleIndex(incompatibility) => {
+                TantivyError::IncompatibleIndex(incompatibility)
+            }
+        }
     }
 }
 
@@ -134,9 +145,35 @@ impl From<schema::DocParsingError> for TantivyError {
     }
 }
 
+impl From<OpenWriteError> for TantivyError {
+    fn from(error: OpenWriteError) -> TantivyError {
+        match error {
+            OpenWriteError::FileAlreadyExists(filepath) => {
+                TantivyError::FileAlreadyExists(filepath)
+            }
+            OpenWriteError::IOError(io_error) => TantivyError::IOError(io_error),
+        }
+    }
+}
+
+impl From<OpenDirectoryError> for TantivyError {
+    fn from(error: OpenDirectoryError) -> TantivyError {
+        match error {
+            OpenDirectoryError::DoesNotExist(directory_path) => {
+                TantivyError::PathDoesNotExist(directory_path)
+            }
+            OpenDirectoryError::NotADirectory(directory_path) => {
+                TantivyError::InvalidArgument(format!("{:?} is not a directory", directory_path))
+            }
+            OpenDirectoryError::IoError(err) => TantivyError::IOError(IOError::from(err)),
+        }
+    }
+}
+
 impl From<serde_json::Error> for TantivyError {
     fn from(error: serde_json::Error) -> TantivyError {
-        TantivyError::IOError(error.into())
+        let io_err = io::Error::from(error);
+        TantivyError::IOError(io_err.into())
     }
 }
 

src/fastfield/bytes/mod.rs

@@ -6,114 +6,31 @@ pub use self::writer::BytesFastFieldWriter;
 
 #[cfg(test)]
 mod tests {
-    use crate::schema::{BytesOptions, IndexRecordOption, Schema, Value};
+    use crate::schema::Schema;
-    use crate::{query::TermQuery, schema::FAST, schema::INDEXED, schema::STORED};
+    use crate::Index;
-    use crate::{DocAddress, DocSet, Index, Searcher, Term};
-    use std::ops::Deref;
 
     #[test]
-    fn test_bytes() -> crate::Result<()> {
+    fn test_bytes() {
         let mut schema_builder = Schema::builder();
-        let bytes_field = schema_builder.add_bytes_field("bytesfield", FAST);
+        let field = schema_builder.add_bytes_field("bytesfield");
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-        index_writer.add_document(doc!(bytes_field=>vec![0u8, 1, 2, 3]));
+        index_writer.add_document(doc!(field=>vec![0u8, 1, 2, 3]));
-        index_writer.add_document(doc!(bytes_field=>vec![]));
+        index_writer.add_document(doc!(field=>vec![]));
-        index_writer.add_document(doc!(bytes_field=>vec![255u8]));
+        index_writer.add_document(doc!(field=>vec![255u8]));
-        index_writer.add_document(doc!(bytes_field=>vec![1u8, 3, 5, 7, 9]));
+        index_writer.add_document(doc!(field=>vec![1u8, 3, 5, 7, 9]));
-        index_writer.add_document(doc!(bytes_field=>vec![0u8; 1000]));
+        index_writer.add_document(doc!(field=>vec![0u8; 1000]));
-        index_writer.commit()?;
+        assert!(index_writer.commit().is_ok());
-        let searcher = index.reader()?.searcher();
+        let searcher = index.reader().unwrap().searcher();
         let segment_reader = searcher.segment_reader(0);
-        let bytes_reader = segment_reader.fast_fields().bytes(bytes_field).unwrap();
+        let bytes_reader = segment_reader.fast_fields().bytes(field).unwrap();
+
         assert_eq!(bytes_reader.get_bytes(0), &[0u8, 1, 2, 3]);
         assert!(bytes_reader.get_bytes(1).is_empty());
         assert_eq!(bytes_reader.get_bytes(2), &[255u8]);
         assert_eq!(bytes_reader.get_bytes(3), &[1u8, 3, 5, 7, 9]);
         let long = vec![0u8; 1000];
         assert_eq!(bytes_reader.get_bytes(4), long.as_slice());
-        Ok(())
-    }
-
-    fn create_index_for_test<T: Into<BytesOptions>>(
-        byte_options: T,
-    ) -> crate::Result<impl Deref<Target = Searcher>> {
-        let mut schema_builder = Schema::builder();
-        let field = schema_builder.add_bytes_field("string_bytes", byte_options.into());
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(
-                field => b"tantivy".as_ref(),
-                field => b"lucene".as_ref()
-        ));
-        index_writer.commit()?;
-        Ok(index.reader()?.searcher())
-    }
-
-    #[test]
-    fn test_stored_bytes() -> crate::Result<()> {
-        let searcher = create_index_for_test(STORED)?;
-        assert_eq!(searcher.num_docs(), 1);
-        let retrieved_doc = searcher.doc(DocAddress(0u32, 0u32))?;
-        let field = searcher.schema().get_field("string_bytes").unwrap();
-        let values: Vec<&Value> = retrieved_doc.get_all(field).collect();
-        assert_eq!(values.len(), 2);
-        let values_bytes: Vec<&[u8]> = values
-            .into_iter()
-            .flat_map(|value| value.bytes_value())
-            .collect();
-        assert_eq!(values_bytes, &[&b"tantivy"[..], &b"lucene"[..]]);
-        Ok(())
-    }
-
-    #[test]
-    fn test_non_stored_bytes() -> crate::Result<()> {
-        let searcher = create_index_for_test(INDEXED)?;
-        assert_eq!(searcher.num_docs(), 1);
-        let retrieved_doc = searcher.doc(DocAddress(0u32, 0u32))?;
-        let field = searcher.schema().get_field("string_bytes").unwrap();
-        assert!(retrieved_doc.get_first(field).is_none());
-        Ok(())
-    }
-
-    #[test]
-    fn test_index_bytes() -> crate::Result<()> {
-        let searcher = create_index_for_test(INDEXED)?;
-        assert_eq!(searcher.num_docs(), 1);
-        let field = searcher.schema().get_field("string_bytes").unwrap();
-        let term = Term::from_field_bytes(field, b"lucene".as_ref());
-        let term_query = TermQuery::new(term, IndexRecordOption::Basic);
-        let term_weight = term_query.specialized_weight(&searcher, true)?;
-        let term_scorer = term_weight.specialized_scorer(searcher.segment_reader(0), 1.0)?;
-        assert_eq!(term_scorer.doc(), 0u32);
-        Ok(())
-    }
-
-    #[test]
-    fn test_non_index_bytes() -> crate::Result<()> {
-        let searcher = create_index_for_test(STORED)?;
-        assert_eq!(searcher.num_docs(), 1);
-        let field = searcher.schema().get_field("string_bytes").unwrap();
-        let term = Term::from_field_bytes(field, b"lucene".as_ref());
-        let term_query = TermQuery::new(term, IndexRecordOption::Basic);
-        let term_weight_err = term_query.specialized_weight(&searcher, false);
-        assert!(matches!(
-            term_weight_err,
-            Err(crate::TantivyError::SchemaError(_))
-        ));
-        Ok(())
-    }
-
-    #[test]
-    fn test_fast_bytes_multivalue_value() -> crate::Result<()> {
-        let searcher = create_index_for_test(FAST)?;
-        assert_eq!(searcher.num_docs(), 1);
-        let fast_fields = searcher.segment_reader(0u32).fast_fields();
-        let field = searcher.schema().get_field("string_bytes").unwrap();
-        let fast_field_reader = fast_fields.bytes(field).unwrap();
-        assert_eq!(fast_field_reader.get_bytes(0u32), b"tantivy");
-        Ok(())
     }
 }

src/fastfield/bytes/reader.rs

@@ -1,5 +1,6 @@
-use crate::directory::FileSlice;
+use owning_ref::OwningRef;
-use crate::directory::OwnedBytes;
+
+use crate::directory::ReadOnlySource;
 use crate::fastfield::FastFieldReader;
 use crate::DocId;
 
@@ -16,16 +17,16 @@ use crate::DocId;
 #[derive(Clone)]
 pub struct BytesFastFieldReader {
     idx_reader: FastFieldReader<u64>,
-    values: OwnedBytes,
+    values: OwningRef<ReadOnlySource, [u8]>,
 }
 
 impl BytesFastFieldReader {
     pub(crate) fn open(
         idx_reader: FastFieldReader<u64>,
-        values_file: FileSlice,
+        values_source: ReadOnlySource,
-    ) -> crate::Result<BytesFastFieldReader> {
+    ) -> BytesFastFieldReader {
-        let values = values_file.read_bytes()?;
+        let values = OwningRef::new(values_source).map(|source| &source[..]);
-        Ok(BytesFastFieldReader { idx_reader, values })
+        BytesFastFieldReader { idx_reader, values }
     }
 
     fn range(&self, doc: DocId) -> (usize, usize) {
@@ -37,7 +38,7 @@ impl BytesFastFieldReader {
     /// Returns the bytes associated to the given `doc`
     pub fn get_bytes(&self, doc: DocId) -> &[u8] {
         let (start, stop) = self.range(doc);
-        &self.values.as_slice()[start..stop]
+        &self.values[start..stop]
     }
 
     /// Returns the overall number of bytes in this bytes fast field.

src/fastfield/bytes/writer.rs

@@ -49,10 +49,16 @@ impl BytesFastFieldWriter {
     /// matching field values present in the document.
     pub fn add_document(&mut self, doc: &Document) {
         self.next_doc();
-        for field_value in doc.get_all(self.field) {
+        for field_value in doc.field_values() {
-            if let Value::Bytes(ref bytes) = field_value {
+            if field_value.field() == self.field {
-                self.vals.extend_from_slice(bytes);
+                if let Value::Bytes(ref bytes) = *field_value.value() {
-                return;
+                    self.vals.extend_from_slice(bytes);
+                } else {
+                    panic!(
+                        "Bytes field contained non-Bytes Value!. Field {:?} = {:?}",
+                        self.field, field_value
+                    );
+                }
             }
         }
     }
@@ -70,18 +76,21 @@ impl BytesFastFieldWriter {
 
     /// Serializes the fast field values by pushing them to the `FastFieldSerializer`.
     pub fn serialize(&self, serializer: &mut FastFieldSerializer) -> io::Result<()> {
-        // writing the offset index
+        {
-        let mut doc_index_serializer =
+            // writing the offset index
-            serializer.new_u64_fast_field_with_idx(self.field, 0, self.vals.len() as u64, 0)?;
+            let mut doc_index_serializer =
-        for &offset in &self.doc_index {
+                serializer.new_u64_fast_field_with_idx(self.field, 0, self.vals.len() as u64, 0)?;
-            doc_index_serializer.add_val(offset)?;
+            for &offset in &self.doc_index {
+                doc_index_serializer.add_val(offset)?;
+            }
+            doc_index_serializer.add_val(self.vals.len() as u64)?;
+            doc_index_serializer.close_field()?;
+        }
+        {
+            // writing the values themselves
+            let mut value_serializer = serializer.new_bytes_fast_field_with_idx(self.field, 1)?;
+            value_serializer.write_all(&self.vals)?;
         }
-        doc_index_serializer.add_val(self.vals.len() as u64)?;
-        doc_index_serializer.close_field()?;
-        // writing the values themselves
-        serializer
-            .new_bytes_fast_field_with_idx(self.field, 1)?
-            .write_all(&self.vals)?;
         Ok(())
     }
 }

src/fastfield/delete.rs

@@ -1,6 +1,5 @@
 use crate::common::{BitSet, HasLen};
-use crate::directory::FileSlice;
+use crate::directory::ReadOnlySource;
-use crate::directory::OwnedBytes;
 use crate::directory::WritePtr;
 use crate::space_usage::ByteCount;
 use crate::DocId;
@@ -10,8 +9,6 @@ use std::io::Write;
 /// Write a delete `BitSet`
 ///
 /// where `delete_bitset` is the set of deleted `DocId`.
-/// Warning: this function does not call terminate. The caller is in charge of
-/// closing the writer properly.
 pub fn write_delete_bitset(
     delete_bitset: &BitSet,
     max_doc: u32,
@@ -40,41 +37,22 @@ pub fn write_delete_bitset(
 /// Set of deleted `DocId`s.
 #[derive(Clone)]
 pub struct DeleteBitSet {
-    data: OwnedBytes,
+    data: ReadOnlySource,
     len: usize,
 }
 
 impl DeleteBitSet {
-    #[cfg(test)]
+    /// Opens a delete bitset given its data source.
-    pub(crate) fn for_test(docs: &[DocId], max_doc: u32) -> DeleteBitSet {
+    pub fn open(data: ReadOnlySource) -> DeleteBitSet {
-        use crate::directory::{Directory, RAMDirectory, TerminatingWrite};
+        let num_deleted: usize = data
-        use std::path::Path;
-        assert!(docs.iter().all(|&doc| doc < max_doc));
-        let mut bitset = BitSet::with_max_value(max_doc);
-        for &doc in docs {
-            bitset.insert(doc);
-        }
-        let directory = RAMDirectory::create();
-        let path = Path::new("dummydeletebitset");
-        let mut wrt = directory.open_write(path).unwrap();
-        write_delete_bitset(&bitset, max_doc, &mut wrt).unwrap();
-        wrt.terminate().unwrap();
-        let file = directory.open_read(path).unwrap();
-        Self::open(file).unwrap()
-    }
-
-    /// Opens a delete bitset given its file.
-    pub fn open(file: FileSlice) -> crate::Result<DeleteBitSet> {
-        let bytes = file.read_bytes()?;
-        let num_deleted: usize = bytes
             .as_slice()
             .iter()
             .map(|b| b.count_ones() as usize)
             .sum();
-        Ok(DeleteBitSet {
+        DeleteBitSet {
-            data: bytes,
+            data,
             len: num_deleted,
-        })
+        }
     }
 
     /// Returns true iff the document is still "alive". In other words, if it has not been deleted.
@@ -86,7 +64,7 @@ impl DeleteBitSet {
     #[inline(always)]
     pub fn is_deleted(&self, doc: DocId) -> bool {
         let byte_offset = doc / 8u32;
-        let b: u8 = self.data.as_slice()[byte_offset as usize];
+        let b: u8 = (*self.data)[byte_offset as usize];
         let shift = (doc & 7u32) as u8;
         b & (1u8 << shift) != 0
     }
@@ -105,35 +83,42 @@ impl HasLen for DeleteBitSet {
 
 #[cfg(test)]
 mod tests {
-    use super::DeleteBitSet;
+    use super::*;
-    use crate::common::HasLen;
+    use crate::directory::*;
+    use std::path::PathBuf;
 
-    #[test]
+    fn test_delete_bitset_helper(bitset: &BitSet, max_doc: u32) {
-    fn test_delete_bitset_empty() {
+        let test_path = PathBuf::from("test");
-        let delete_bitset = DeleteBitSet::for_test(&[], 10);
+        let mut directory = RAMDirectory::default();
-        for doc in 0..10 {
+        {
-            assert_eq!(delete_bitset.is_deleted(doc), !delete_bitset.is_alive(doc));
+            let mut writer = directory.open_write(&*test_path).unwrap();
+            write_delete_bitset(bitset, max_doc, &mut writer).unwrap();
+            writer.terminate().unwrap();
         }
-        assert_eq!(delete_bitset.len(), 0);
+        let source = directory.open_read(&test_path).unwrap();
+        let delete_bitset = DeleteBitSet::open(source);
+        for doc in 0..max_doc {
+            assert_eq!(bitset.contains(doc), delete_bitset.is_deleted(doc as DocId));
+        }
+        assert_eq!(delete_bitset.len(), bitset.len());
     }
 
     #[test]
     fn test_delete_bitset() {
-        let delete_bitset = DeleteBitSet::for_test(&[1, 9], 10);
+        {
-        assert!(delete_bitset.is_alive(0));
+            let mut bitset = BitSet::with_max_value(10);
-        assert!(delete_bitset.is_deleted(1));
+            bitset.insert(1);
-        assert!(delete_bitset.is_alive(2));
+            bitset.insert(9);
-        assert!(delete_bitset.is_alive(3));
+            test_delete_bitset_helper(&bitset, 10);
-        assert!(delete_bitset.is_alive(4));
+        }
-        assert!(delete_bitset.is_alive(5));
+        {
-        assert!(delete_bitset.is_alive(6));
+            let mut bitset = BitSet::with_max_value(8);
-        assert!(delete_bitset.is_alive(6));
+            bitset.insert(1);
-        assert!(delete_bitset.is_alive(7));
+            bitset.insert(2);
-        assert!(delete_bitset.is_alive(8));
+            bitset.insert(3);
-        assert!(delete_bitset.is_deleted(9));
+            bitset.insert(5);
-        for doc in 0..10 {
+            bitset.insert(7);
-            assert_eq!(delete_bitset.is_deleted(doc), !delete_bitset.is_alive(doc));
+            test_delete_bitset_helper(&bitset, 8);
         }
-        assert_eq!(delete_bitset.len(), 2);
     }
 }

src/fastfield/error.rs

@@ -4,8 +4,8 @@ use std::result;
 /// `FastFieldNotAvailableError` is returned when the
 /// user requested for a fast field reader, and the field was not
 /// defined in the schema as a fast field.
-#[derive(Debug, Error)]
+#[derive(Debug, Fail)]
-#[error("Fast field not available: '{field_name:?}'")]
+#[fail(display = "Fast field not available: '{:?}'", field_name)]
 pub struct FastFieldNotAvailableError {
     field_name: String,
 }

src/fastfield/facet_reader.rs

@@ -1,5 +1,4 @@
 use super::MultiValueIntFastFieldReader;
-use crate::error::DataCorruption;
 use crate::schema::Facet;
 use crate::termdict::TermDictionary;
 use crate::termdict::TermOrdinal;
@@ -63,73 +62,18 @@ impl FacetReader {
         &mut self,
         facet_ord: TermOrdinal,
         output: &mut Facet,
-    ) -> crate::Result<()> {
+    ) -> Result<(), str::Utf8Error> {
         let found_term = self
             .term_dict
-            .ord_to_term(facet_ord as u64, &mut self.buffer)?;
+            .ord_to_term(facet_ord as u64, &mut self.buffer);
         assert!(found_term, "Term ordinal {} no found.", facet_ord);
-        let facet_str = str::from_utf8(&self.buffer[..])
+        let facet_str = str::from_utf8(&self.buffer[..])?;
-            .map_err(|utf8_err| DataCorruption::comment_only(utf8_err.to_string()))?;
         output.set_facet_str(facet_str);
         Ok(())
     }
 
     /// Return the list of facet ordinals associated to a document.
-    pub fn facet_ords(&self, doc: DocId, output: &mut Vec<u64>) {
+    pub fn facet_ords(&mut self, doc: DocId, output: &mut Vec<u64>) {
         self.term_ords.get_vals(doc, output);
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use crate::Index;
-    use crate::{
-        schema::{Facet, SchemaBuilder},
-        Document,
-    };
-
-    #[test]
-    fn test_facet_not_populated_for_all_docs() -> crate::Result<()> {
-        let mut schema_builder = SchemaBuilder::default();
-        let facet_field = schema_builder.add_facet_field("facet");
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(facet_field=>Facet::from_text("/a/b")));
-        index_writer.add_document(Document::default());
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let facet_reader = searcher
-            .segment_reader(0u32)
-            .facet_reader(facet_field)
-            .unwrap();
-        let mut facet_ords = Vec::new();
-        facet_reader.facet_ords(0u32, &mut facet_ords);
-        assert_eq!(&facet_ords, &[2u64]);
-        facet_reader.facet_ords(1u32, &mut facet_ords);
-        assert!(facet_ords.is_empty());
-        Ok(())
-    }
-    #[test]
-    fn test_facet_not_populated_for_any_docs() -> crate::Result<()> {
-        let mut schema_builder = SchemaBuilder::default();
-        let facet_field = schema_builder.add_facet_field("facet");
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(Document::default());
-        index_writer.add_document(Document::default());
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let facet_reader = searcher
-            .segment_reader(0u32)
-            .facet_reader(facet_field)
-            .unwrap();
-        let mut facet_ords = Vec::new();
-        facet_reader.facet_ords(0u32, &mut facet_ords);
-        assert!(facet_ords.is_empty());
-        facet_reader.facet_ords(1u32, &mut facet_ords);
-        assert!(facet_ords.is_empty());
-        Ok(())
-    }
-}

src/fastfield/mod.rs

@@ -33,14 +33,11 @@ pub use self::reader::FastFieldReader;
 pub use self::readers::FastFieldReaders;
 pub use self::serializer::FastFieldSerializer;
 pub use self::writer::{FastFieldsWriter, IntFastFieldWriter};
+use crate::chrono::{NaiveDateTime, Utc};
 use crate::common;
 use crate::schema::Cardinality;
 use crate::schema::FieldType;
 use crate::schema::Value;
-use crate::{
-    chrono::{NaiveDateTime, Utc},
-    schema::Type,
-};
 
 mod bytes;
 mod delete;
@@ -79,9 +76,6 @@ pub trait FastValue: Clone + Copy + Send + Sync + PartialOrd {
     fn make_zero() -> Self {
         Self::from_u64(0i64.to_u64())
     }
-
-    /// Returns the `schema::Type` for this FastValue.
-    fn to_type() -> Type;
 }
 
 impl FastValue for u64 {
@@ -104,10 +98,6 @@ impl FastValue for u64 {
     fn as_u64(&self) -> u64 {
         *self
     }
-
-    fn to_type() -> Type {
-        Type::U64
-    }
 }
 
 impl FastValue for i64 {
@@ -129,10 +119,6 @@ impl FastValue for i64 {
     fn as_u64(&self) -> u64 {
         *self as u64
     }
-
-    fn to_type() -> Type {
-        Type::I64
-    }
 }
 
 impl FastValue for f64 {
@@ -154,10 +140,6 @@ impl FastValue for f64 {
     fn as_u64(&self) -> u64 {
         self.to_bits()
     }
-
-    fn to_type() -> Type {
-        Type::F64
-    }
 }
 
 impl FastValue for crate::DateTime {
@@ -180,10 +162,6 @@ impl FastValue for crate::DateTime {
     fn as_u64(&self) -> u64 {
         self.timestamp().as_u64()
     }
-
-    fn to_type() -> Type {
-        Type::Date
-    }
 }
 
 fn value_to_u64(value: &Value) -> u64 {
@@ -209,7 +187,6 @@ mod tests {
     use crate::schema::FAST;
     use crate::schema::{Document, IntOptions};
     use crate::{Index, SegmentId, SegmentReader};
-    use common::HasLen;
     use once_cell::sync::Lazy;
     use rand::prelude::SliceRandom;
     use rand::rngs::StdRng;
@@ -240,9 +217,9 @@ mod tests {
     }
 
     #[test]
-    fn test_intfastfield_small() -> crate::Result<()> {
+    fn test_intfastfield_small() {
         let path = Path::new("test");
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
         {
             let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
             let mut serializer = FastFieldSerializer::from_write(write).unwrap();
@@ -255,24 +232,27 @@ mod tests {
                 .unwrap();
             serializer.close().unwrap();
         }
-        let file = directory.open_read(&path).unwrap();
+        let source = directory.open_read(&path).unwrap();
-        assert_eq!(file.len(), 36 as usize);
+        {
-        let composite_file = CompositeFile::open(&file)?;
+            assert_eq!(source.len(), 36 as usize);
-        let file = composite_file.open_read(*FIELD).unwrap();
+        }
-        let fast_field_reader = FastFieldReader::<u64>::open(file)?;
+        {
-        assert_eq!(fast_field_reader.get(0), 13u64);
+            let composite_file = CompositeFile::open(&source).unwrap();
-        assert_eq!(fast_field_reader.get(1), 14u64);
+            let field_source = composite_file.open_read(*FIELD).unwrap();
-        assert_eq!(fast_field_reader.get(2), 2u64);
+            let fast_field_reader = FastFieldReader::<u64>::open(field_source);
-        Ok(())
+            assert_eq!(fast_field_reader.get(0), 13u64);
+            assert_eq!(fast_field_reader.get(1), 14u64);
+            assert_eq!(fast_field_reader.get(2), 2u64);
+        }
     }
 
     #[test]
-    fn test_intfastfield_large() -> crate::Result<()> {
+    fn test_intfastfield_large() {
         let path = Path::new("test");
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
         {
-            let write: WritePtr = directory.open_write(Path::new("test"))?;
+            let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
-            let mut serializer = FastFieldSerializer::from_write(write)?;
+            let mut serializer = FastFieldSerializer::from_write(write).unwrap();
             let mut fast_field_writers = FastFieldsWriter::from_schema(&SCHEMA);
             fast_field_writers.add_document(&doc!(*FIELD=>4u64));
             fast_field_writers.add_document(&doc!(*FIELD=>14_082_001u64));
@@ -283,15 +263,19 @@ mod tests {
             fast_field_writers.add_document(&doc!(*FIELD=>1_002u64));
             fast_field_writers.add_document(&doc!(*FIELD=>1_501u64));
             fast_field_writers.add_document(&doc!(*FIELD=>215u64));
-            fast_field_writers.serialize(&mut serializer, &HashMap::new())?;
+            fast_field_writers
-            serializer.close()?;
+                .serialize(&mut serializer, &HashMap::new())
+                .unwrap();
+            serializer.close().unwrap();
         }
-        let file = directory.open_read(&path)?;
+        let source = directory.open_read(&path).unwrap();
-        assert_eq!(file.len(), 61 as usize);
         {
-            let fast_fields_composite = CompositeFile::open(&file)?;
+            assert_eq!(source.len(), 61 as usize);
+        }
+        {
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(*FIELD).unwrap();
-            let fast_field_reader = FastFieldReader::<u64>::open(data)?;
+            let fast_field_reader = FastFieldReader::<u64>::open(data);
             assert_eq!(fast_field_reader.get(0), 4u64);
             assert_eq!(fast_field_reader.get(1), 14_082_001u64);
             assert_eq!(fast_field_reader.get(2), 3_052u64);
@@ -302,13 +286,12 @@ mod tests {
             assert_eq!(fast_field_reader.get(7), 1_501u64);
             assert_eq!(fast_field_reader.get(8), 215u64);
         }
-        Ok(())
     }
 
     #[test]
-    fn test_intfastfield_null_amplitude() -> crate::Result<()> {
+    fn test_intfastfield_null_amplitude() {
         let path = Path::new("test");
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
 
         {
             let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
@@ -322,23 +305,24 @@ mod tests {
                 .unwrap();
             serializer.close().unwrap();
         }
-        let file = directory.open_read(&path).unwrap();
+        let source = directory.open_read(&path).unwrap();
-        assert_eq!(file.len(), 34 as usize);
         {
-            let fast_fields_composite = CompositeFile::open(&file).unwrap();
+            assert_eq!(source.len(), 34 as usize);
+        }
+        {
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(*FIELD).unwrap();
-            let fast_field_reader = FastFieldReader::<u64>::open(data)?;
+            let fast_field_reader = FastFieldReader::<u64>::open(data);
             for doc in 0..10_000 {
                 assert_eq!(fast_field_reader.get(doc), 100_000u64);
             }
         }
-        Ok(())
     }
 
     #[test]
-    fn test_intfastfield_large_numbers() -> crate::Result<()> {
+    fn test_intfastfield_large_numbers() {
         let path = Path::new("test");
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
 
         {
             let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
@@ -354,12 +338,14 @@ mod tests {
                 .unwrap();
             serializer.close().unwrap();
         }
-        let file = directory.open_read(&path).unwrap();
+        let source = directory.open_read(&path).unwrap();
-        assert_eq!(file.len(), 80042 as usize);
         {
-            let fast_fields_composite = CompositeFile::open(&file)?;
+            assert_eq!(source.len(), 80042 as usize);
+        }
+        {
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(*FIELD).unwrap();
-            let fast_field_reader = FastFieldReader::<u64>::open(data)?;
+            let fast_field_reader = FastFieldReader::<u64>::open(data);
             assert_eq!(fast_field_reader.get(0), 0u64);
             for doc in 1..10_001 {
                 assert_eq!(
@@ -368,13 +354,12 @@ mod tests {
                 );
             }
         }
-        Ok(())
     }
 
     #[test]
-    fn test_signed_intfastfield() -> crate::Result<()> {
+    fn test_signed_intfastfield() {
         let path = Path::new("test");
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
         let mut schema_builder = Schema::builder();
 
         let i64_field = schema_builder.add_i64_field("field", FAST);
@@ -393,12 +378,14 @@ mod tests {
                 .unwrap();
             serializer.close().unwrap();
         }
-        let file = directory.open_read(&path).unwrap();
+        let source = directory.open_read(&path).unwrap();
-        assert_eq!(file.len(), 17709 as usize);
         {
-            let fast_fields_composite = CompositeFile::open(&file)?;
+            assert_eq!(source.len(), 17709 as usize);
+        }
+        {
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(i64_field).unwrap();
-            let fast_field_reader = FastFieldReader::<i64>::open(data)?;
+            let fast_field_reader = FastFieldReader::<i64>::open(data);
 
             assert_eq!(fast_field_reader.min_value(), -100i64);
             assert_eq!(fast_field_reader.max_value(), 9_999i64);
@@ -411,13 +398,12 @@ mod tests {
                 assert_eq!(buffer[i], -100i64 + 53i64 + i as i64);
             }
         }
-        Ok(())
     }
 
     #[test]
-    fn test_signed_intfastfield_default_val() -> crate::Result<()> {
+    fn test_signed_intfastfield_default_val() {
         let path = Path::new("test");
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
         let mut schema_builder = Schema::builder();
         let i64_field = schema_builder.add_i64_field("field", FAST);
         let schema = schema_builder.build();
@@ -434,14 +420,13 @@ mod tests {
             serializer.close().unwrap();
         }
 
-        let file = directory.open_read(&path).unwrap();
+        let source = directory.open_read(&path).unwrap();
         {
-            let fast_fields_composite = CompositeFile::open(&file).unwrap();
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(i64_field).unwrap();
-            let fast_field_reader = FastFieldReader::<i64>::open(data)?;
+            let fast_field_reader = FastFieldReader::<i64>::open(data);
             assert_eq!(fast_field_reader.get(0u32), 0i64);
         }
-        Ok(())
     }
 
     // Warning: this generates the same permutation at each call
@@ -452,26 +437,28 @@ mod tests {
     }
 
     #[test]
-    fn test_intfastfield_permutation() -> crate::Result<()> {
+    fn test_intfastfield_permutation() {
         let path = Path::new("test");
         let permutation = generate_permutation();
         let n = permutation.len();
-        let directory = RAMDirectory::create();
+        let mut directory = RAMDirectory::create();
         {
-            let write: WritePtr = directory.open_write(Path::new("test"))?;
+            let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
-            let mut serializer = FastFieldSerializer::from_write(write)?;
+            let mut serializer = FastFieldSerializer::from_write(write).unwrap();
             let mut fast_field_writers = FastFieldsWriter::from_schema(&SCHEMA);
             for &x in &permutation {
                 fast_field_writers.add_document(&doc!(*FIELD=>x));
             }
-            fast_field_writers.serialize(&mut serializer, &HashMap::new())?;
+            fast_field_writers
-            serializer.close()?;
+                .serialize(&mut serializer, &HashMap::new())
+                .unwrap();
+            serializer.close().unwrap();
         }
-        let file = directory.open_read(&path)?;
+        let source = directory.open_read(&path).unwrap();
         {
-            let fast_fields_composite = CompositeFile::open(&file)?;
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(*FIELD).unwrap();
-            let fast_field_reader = FastFieldReader::<u64>::open(data)?;
+            let fast_field_reader = FastFieldReader::<u64>::open(data);
 
             let mut a = 0u64;
             for _ in 0..n {
@@ -479,7 +466,6 @@ mod tests {
                 a = fast_field_reader.get(a as u32);
             }
         }
-        Ok(())
     }
 
     #[test]
@@ -488,7 +474,7 @@ mod tests {
         let date_field = schema_builder.add_date_field("date", FAST);
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.set_merge_policy(Box::new(NoMergePolicy));
         index_writer.add_document(doc!(date_field =>crate::chrono::prelude::Utc::now()));
         index_writer.commit().unwrap();
@@ -525,7 +511,7 @@ mod tests {
         );
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.set_merge_policy(Box::new(NoMergePolicy));
         index_writer.add_document(doc!(
             date_field => crate::DateTime::from_u64(1i64.to_u64()),
@@ -612,7 +598,7 @@ mod bench {
     fn bench_intfastfield_linear_fflookup(b: &mut Bencher) {
         let path = Path::new("test");
         let permutation = generate_permutation();
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
         {
             let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
             let mut serializer = FastFieldSerializer::from_write(write).unwrap();
@@ -625,11 +611,11 @@ mod bench {
                 .unwrap();
             serializer.close().unwrap();
         }
-        let file = directory.open_read(&path).unwrap();
+        let source = directory.open_read(&path).unwrap();
         {
-            let fast_fields_composite = CompositeFile::open(&file).unwrap();
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(*FIELD).unwrap();
-            let fast_field_reader = FastFieldReader::<u64>::open(data).unwrap();
+            let fast_field_reader = FastFieldReader::<u64>::open(data);
 
             b.iter(|| {
                 let n = test::black_box(7000u32);
@@ -646,7 +632,7 @@ mod bench {
     fn bench_intfastfield_fflookup(b: &mut Bencher) {
         let path = Path::new("test");
         let permutation = generate_permutation();
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
         {
             let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
             let mut serializer = FastFieldSerializer::from_write(write).unwrap();
@@ -659,11 +645,11 @@ mod bench {
                 .unwrap();
             serializer.close().unwrap();
         }
-        let file = directory.open_read(&path).unwrap();
+        let source = directory.open_read(&path).unwrap();
         {
-            let fast_fields_composite = CompositeFile::open(&file).unwrap();
+            let fast_fields_composite = CompositeFile::open(&source).unwrap();
             let data = fast_fields_composite.open_read(*FIELD).unwrap();
-            let fast_field_reader = FastFieldReader::<u64>::open(data).unwrap();
+            let fast_field_reader = FastFieldReader::<u64>::open(data);
 
             b.iter(|| {
                 let n = test::black_box(1000u32);

src/fastfield/multivalued/mod.rs

@@ -25,7 +25,7 @@ mod tests {
         );
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(field=>1u64, field=>3u64));
         index_writer.add_document(doc!());
         index_writer.add_document(doc!(field=>4u64));
@@ -64,7 +64,7 @@ mod tests {
             schema_builder.add_i64_field("time_stamp_i", IntOptions::default().set_stored());
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let first_time_stamp = chrono::Utc::now();
         index_writer.add_document(
             doc!(date_field=>first_time_stamp, date_field=>first_time_stamp, time_i=>1i64),
@@ -100,7 +100,6 @@ mod tests {
                         .get_first(date_field)
                         .expect("cannot find value")
                         .date_value()
-                        .unwrap()
                         .timestamp(),
                     first_time_stamp.timestamp()
                 );
@@ -109,7 +108,7 @@ mod tests {
                         .get_first(time_i)
                         .expect("cannot find value")
                         .i64_value(),
-                    Some(1i64)
+                    1i64
                 );
             }
         }
@@ -132,7 +131,6 @@ mod tests {
                         .get_first(date_field)
                         .expect("cannot find value")
                         .date_value()
-                        .unwrap()
                         .timestamp(),
                     two_secs_ahead.timestamp()
                 );
@@ -141,7 +139,7 @@ mod tests {
                         .get_first(time_i)
                         .expect("cannot find value")
                         .i64_value(),
-                    Some(3i64)
+                    3i64
                 );
             }
         }
@@ -188,7 +186,7 @@ mod tests {
         );
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(field=> 1i64, field => 3i64));
         index_writer.add_document(doc!());
         index_writer.add_document(doc!(field=> -4i64));
@@ -199,14 +197,22 @@ mod tests {
         let segment_reader = searcher.segment_reader(0);
         let mut vals = Vec::new();
         let multi_value_reader = segment_reader.fast_fields().i64s(field).unwrap();
-        multi_value_reader.get_vals(2, &mut vals);
+        {
-        assert_eq!(&vals, &[-4i64]);
+            multi_value_reader.get_vals(2, &mut vals);
-        multi_value_reader.get_vals(0, &mut vals);
+            assert_eq!(&vals, &[-4i64]);
-        assert_eq!(&vals, &[1i64, 3i64]);
+        }
-        multi_value_reader.get_vals(1, &mut vals);
+        {
-        assert!(vals.is_empty());
+            multi_value_reader.get_vals(0, &mut vals);
-        multi_value_reader.get_vals(3, &mut vals);
+            assert_eq!(&vals, &[1i64, 3i64]);
-        assert_eq!(&vals, &[-5i64, -20i64, 1i64]);
+        }
+        {
+            multi_value_reader.get_vals(1, &mut vals);
+            assert!(vals.is_empty());
+        }
+        {
+            multi_value_reader.get_vals(3, &mut vals);
+            assert_eq!(&vals, &[-5i64, -20i64, 1i64]);
+        }
     }
     #[test]
     #[ignore]
@@ -215,7 +221,7 @@ mod tests {
         let field = schema_builder.add_facet_field("facetfield");
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         for i in 0..100_000 {
             index_writer.add_document(doc!(field=> Facet::from(format!("/lang/{}", i).as_str())));
         }

src/fastfield/multivalued/reader.rs

@@ -74,7 +74,7 @@ mod tests {
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
         let mut index_writer = index
-            .writer_for_tests()
+            .writer_with_num_threads(1, 30_000_000)
             .expect("Failed to create index writer.");
         index_writer.add_document(doc!(
             facet_field => Facet::from("/category/cat2"),

src/fastfield/multivalued/writer.rs

@@ -143,7 +143,7 @@ impl MultiValueIntFastFieldWriter {
                             .iter()
                             .map(|val| *mapping.get(val).expect("Missing term ordinal"));
                         doc_vals.extend(remapped_vals);
-                        doc_vals.sort_unstable();
+                        doc_vals.sort();
                         for &val in &doc_vals {
                             value_serializer.add_val(val)?;
                         }

src/fastfield/reader.rs

@@ -3,12 +3,13 @@ use crate::common::bitpacker::BitUnpacker;
 use crate::common::compute_num_bits;
 use crate::common::BinarySerializable;
 use crate::common::CompositeFile;
-use crate::directory::FileSlice;
+use crate::directory::ReadOnlySource;
 use crate::directory::{Directory, RAMDirectory, WritePtr};
 use crate::fastfield::{FastFieldSerializer, FastFieldsWriter};
 use crate::schema::Schema;
 use crate::schema::FAST;
 use crate::DocId;
+use owning_ref::OwningRef;
 use std::collections::HashMap;
 use std::marker::PhantomData;
 use std::path::Path;
@@ -19,39 +20,37 @@ use std::path::Path;
 /// fast field is required.
 #[derive(Clone)]
 pub struct FastFieldReader<Item: FastValue> {
-    bit_unpacker: BitUnpacker,
+    bit_unpacker: BitUnpacker<OwningRef<ReadOnlySource, [u8]>>,
     min_value_u64: u64,
     max_value_u64: u64,
     _phantom: PhantomData<Item>,
 }
 
 impl<Item: FastValue> FastFieldReader<Item> {
-    /// Opens a fast field given a file.
+    /// Opens a fast field given a source.
-    pub fn open(file: FileSlice) -> crate::Result<Self> {
+    pub fn open(data: ReadOnlySource) -> Self {
-        let mut bytes = file.read_bytes()?;
+        let min_value: u64;
-        let min_value = u64::deserialize(&mut bytes)?;
+        let amplitude: u64;
-        let amplitude = u64::deserialize(&mut bytes)?;
+        {
+            let mut cursor = data.as_slice();
+            min_value =
+                u64::deserialize(&mut cursor).expect("Failed to read the min_value of fast field.");
+            amplitude =
+                u64::deserialize(&mut cursor).expect("Failed to read the amplitude of fast field.");
+        }
         let max_value = min_value + amplitude;
         let num_bits = compute_num_bits(amplitude);
-        let bit_unpacker = BitUnpacker::new(bytes, num_bits);
+        let owning_ref = OwningRef::new(data).map(|data| &data[16..]);
-        Ok(FastFieldReader {
+        let bit_unpacker = BitUnpacker::new(owning_ref, num_bits);
+        FastFieldReader {
             min_value_u64: min_value,
             max_value_u64: max_value,
             bit_unpacker,
             _phantom: PhantomData,
-        })
-    }
-
-    pub(crate) fn into_u64_reader(self) -> FastFieldReader<u64> {
-        FastFieldReader {
-            bit_unpacker: self.bit_unpacker,
-            min_value_u64: self.min_value_u64,
-            max_value_u64: self.max_value_u64,
-            _phantom: PhantomData,
         }
     }
 
-    pub(crate) fn cast<TFastValue: FastValue>(self) -> FastFieldReader<TFastValue> {
+    pub(crate) fn into_u64_reader(self) -> FastFieldReader<u64> {
         FastFieldReader {
             bit_unpacker: self.bit_unpacker,
             min_value_u64: self.min_value_u64,
@@ -136,7 +135,7 @@ impl<Item: FastValue> From<Vec<Item>> for FastFieldReader<Item> {
         let field = schema_builder.add_u64_field("field", FAST);
         let schema = schema_builder.build();
         let path = Path::new("__dummy__");
-        let directory: RAMDirectory = RAMDirectory::create();
+        let mut directory: RAMDirectory = RAMDirectory::create();
         {
             let write: WritePtr = directory
                 .open_write(path)
@@ -158,11 +157,12 @@ impl<Item: FastValue> From<Vec<Item>> for FastFieldReader<Item> {
             serializer.close().unwrap();
         }
 
-        let file = directory.open_read(path).expect("Failed to open the file");
+        let source = directory.open_read(path).expect("Failed to open the file");
-        let composite_file = CompositeFile::open(&file).expect("Failed to read the composite file");
+        let composite_file =
-        let field_file = composite_file
+            CompositeFile::open(&source).expect("Failed to read the composite file");
+        let field_source = composite_file
             .open_read(field)
             .expect("File component not found");
-        FastFieldReader::open(field_file).unwrap()
+        FastFieldReader::open(field_source)
     }
 }

src/fastfield/readers.rs

@@ -1,6 +1,6 @@
 use crate::common::CompositeFile;
+use crate::fastfield::BytesFastFieldReader;
 use crate::fastfield::MultiValueIntFastFieldReader;
-use crate::fastfield::{BytesFastFieldReader, FastValue};
 use crate::fastfield::{FastFieldNotAvailableError, FastFieldReader};
 use crate::schema::{Cardinality, Field, FieldType, Schema};
 use crate::space_usage::PerFieldSpaceUsage;
@@ -68,52 +68,45 @@ impl FastFieldReaders {
         };
         for (field, field_entry) in schema.fields() {
             let field_type = field_entry.field_type();
-            if let FieldType::Bytes(bytes_option) = field_type {
+            if field_type == &FieldType::Bytes {
-                if !bytes_option.is_fast() {
+                let idx_reader = fast_fields_composite
-                    continue;
-                }
-                let fast_field_idx_file = fast_fields_composite
                     .open_read_with_idx(field, 0)
-                    .ok_or_else(|| FastFieldNotAvailableError::new(field_entry))?;
+                    .ok_or_else(|| FastFieldNotAvailableError::new(field_entry))
-                let idx_reader = FastFieldReader::open(fast_field_idx_file)?;
+                    .map(FastFieldReader::open)?;
                 let data = fast_fields_composite
                     .open_read_with_idx(field, 1)
                     .ok_or_else(|| FastFieldNotAvailableError::new(field_entry))?;
-                let bytes_fast_field_reader = BytesFastFieldReader::open(idx_reader, data)?;
                 fast_field_readers
                     .fast_bytes
-                    .insert(field, bytes_fast_field_reader);
+                    .insert(field, BytesFastFieldReader::open(idx_reader, data));
             } else if let Some((fast_type, cardinality)) = type_and_cardinality(field_type) {
                 match cardinality {
                     Cardinality::SingleValue => {
                         if let Some(fast_field_data) = fast_fields_composite.open_read(field) {
                             match fast_type {
                                 FastType::U64 => {
-                                    let fast_field_reader = FastFieldReader::open(fast_field_data)?;
+                                    let fast_field_reader = FastFieldReader::open(fast_field_data);
                                     fast_field_readers
                                         .fast_field_u64
                                         .insert(field, fast_field_reader);
                                 }
                                 FastType::I64 => {
-                                    let fast_field_reader =
+                                    fast_field_readers.fast_field_i64.insert(
-                                        FastFieldReader::open(fast_field_data.clone())?;
+                                        field,
-                                    fast_field_readers
+                                        FastFieldReader::open(fast_field_data.clone()),
-                                        .fast_field_i64
+                                    );
-                                        .insert(field, fast_field_reader);
                                 }
                                 FastType::F64 => {
-                                    let fast_field_reader =
+                                    fast_field_readers.fast_field_f64.insert(
-                                        FastFieldReader::open(fast_field_data.clone())?;
+                                        field,
-                                    fast_field_readers
+                                        FastFieldReader::open(fast_field_data.clone()),
-                                        .fast_field_f64
+                                    );
-                                        .insert(field, fast_field_reader);
                                 }
                                 FastType::Date => {
-                                    let fast_field_reader =
+                                    fast_field_readers.fast_field_date.insert(
-                                        FastFieldReader::open(fast_field_data.clone())?;
+                                        field,
-                                    fast_field_readers
+                                        FastFieldReader::open(fast_field_data.clone()),
-                                        .fast_field_date
+                                    );
-                                        .insert(field, fast_field_reader);
                                 }
                             }
                         } else {
@@ -124,10 +117,10 @@ impl FastFieldReaders {
                         let idx_opt = fast_fields_composite.open_read_with_idx(field, 0);
                         let data_opt = fast_fields_composite.open_read_with_idx(field, 1);
                         if let (Some(fast_field_idx), Some(fast_field_data)) = (idx_opt, data_opt) {
-                            let idx_reader = FastFieldReader::open(fast_field_idx)?;
+                            let idx_reader = FastFieldReader::open(fast_field_idx);
                             match fast_type {
                                 FastType::I64 => {
-                                    let vals_reader = FastFieldReader::open(fast_field_data)?;
+                                    let vals_reader = FastFieldReader::open(fast_field_data);
                                     let multivalued_int_fast_field =
                                         MultiValueIntFastFieldReader::open(idx_reader, vals_reader);
                                     fast_field_readers
@@ -135,7 +128,7 @@ impl FastFieldReaders {
                                         .insert(field, multivalued_int_fast_field);
                                 }
                                 FastType::U64 => {
-                                    let vals_reader = FastFieldReader::open(fast_field_data)?;
+                                    let vals_reader = FastFieldReader::open(fast_field_data);
                                     let multivalued_int_fast_field =
                                         MultiValueIntFastFieldReader::open(idx_reader, vals_reader);
                                     fast_field_readers
@@ -143,7 +136,7 @@ impl FastFieldReaders {
                                         .insert(field, multivalued_int_fast_field);
                                 }
                                 FastType::F64 => {
-                                    let vals_reader = FastFieldReader::open(fast_field_data)?;
+                                    let vals_reader = FastFieldReader::open(fast_field_data);
                                     let multivalued_int_fast_field =
                                         MultiValueIntFastFieldReader::open(idx_reader, vals_reader);
                                     fast_field_readers
@@ -151,7 +144,7 @@ impl FastFieldReaders {
                                         .insert(field, multivalued_int_fast_field);
                                 }
                                 FastType::Date => {
-                                    let vals_reader = FastFieldReader::open(fast_field_data)?;
+                                    let vals_reader = FastFieldReader::open(fast_field_data);
                                     let multivalued_int_fast_field =
                                         MultiValueIntFastFieldReader::open(idx_reader, vals_reader);
                                     fast_field_readers
@@ -201,14 +194,6 @@ impl FastFieldReaders {
         None
     }
 
-    pub(crate) fn typed_fast_field_reader<TFastValue: FastValue>(
-        &self,
-        field: Field,
-    ) -> Option<FastFieldReader<TFastValue>> {
-        self.u64_lenient(field)
-            .map(|fast_field_reader| fast_field_reader.cast())
-    }
-
     /// Returns the `i64` fast field reader reader associated to `field`.
     ///
     /// If `field` is not a i64 fast field, this method returns `None`.

src/fastfield/writer.rs

@@ -33,7 +33,7 @@ impl FastFieldsWriter {
         let mut bytes_value_writers = Vec::new();
 
         for (field, field_entry) in schema.fields() {
-            match field_entry.field_type() {
+            match *field_entry.field_type() {
                 FieldType::I64(ref int_options)
                 | FieldType::U64(ref int_options)
                 | FieldType::F64(ref int_options)
@@ -56,11 +56,9 @@ impl FastFieldsWriter {
                     let fast_field_writer = MultiValueIntFastFieldWriter::new(field, true);
                     multi_values_writers.push(fast_field_writer);
                 }
-                FieldType::Bytes(bytes_option) => {
+                FieldType::Bytes => {
-                    if bytes_option.is_fast() {
+                    let fast_field_writer = BytesFastFieldWriter::new(field);
-                        let fast_field_writer = BytesFastFieldWriter::new(field);
+                    bytes_value_writers.push(fast_field_writer);
-                        bytes_value_writers.push(fast_field_writer);
-                    }
                 }
                 _ => {}
             }
@@ -128,7 +126,6 @@ impl FastFieldsWriter {
         for field_writer in &self.single_value_writers {
             field_writer.serialize(serializer)?;
         }
-
         for field_writer in &self.multi_values_writers {
             let field = field_writer.field();
             field_writer.serialize(serializer, mapping.get(&field))?;

src/fieldnorm/mod.rs

@@ -21,7 +21,7 @@ mod reader;
 mod serializer;
 mod writer;
 
-pub use self::reader::{FieldNormReader, FieldNormReaders};
+pub use self::reader::FieldNormReader;
 pub use self::serializer::FieldNormsSerializer;
 pub use self::writer::FieldNormsWriter;
 

src/fieldnorm/reader.rs

@@ -1,47 +1,6 @@
 use super::{fieldnorm_to_id, id_to_fieldnorm};
-use crate::common::CompositeFile;
+use crate::directory::ReadOnlySource;
-use crate::directory::FileSlice;
-use crate::directory::OwnedBytes;
-use crate::schema::Field;
-use crate::space_usage::PerFieldSpaceUsage;
 use crate::DocId;
-use std::sync::Arc;
-
-/// Reader for the fieldnorm (for each document, the number of tokens indexed in the
-/// field) of all indexed fields in the index.
-///
-/// Each fieldnorm is approximately compressed over one byte. We refer to this byte as
-/// `fieldnorm_id`.
-/// The mapping from `fieldnorm` to `fieldnorm_id` is given by monotonic.
-#[derive(Clone)]
-pub struct FieldNormReaders {
-    data: Arc<CompositeFile>,
-}
-
-impl FieldNormReaders {
-    /// Creates a field norm reader.
-    pub fn open(file: FileSlice) -> crate::Result<FieldNormReaders> {
-        let data = CompositeFile::open(&file)?;
-        Ok(FieldNormReaders {
-            data: Arc::new(data),
-        })
-    }
-
-    /// Returns the FieldNormReader for a specific field.
-    pub fn get_field(&self, field: Field) -> crate::Result<Option<FieldNormReader>> {
-        if let Some(file) = self.data.open_read(field) {
-            let fieldnorm_reader = FieldNormReader::open(file)?;
-            Ok(Some(fieldnorm_reader))
-        } else {
-            Ok(None)
-        }
-    }
-
-    /// Return a break down of the space usage per field.
-    pub fn space_usage(&self) -> PerFieldSpaceUsage {
-        self.data.space_usage()
-    }
-}
 
 /// Reads the fieldnorm associated to a document.
 /// The fieldnorm represents the length associated to
@@ -60,57 +19,14 @@ impl FieldNormReaders {
 /// Apart from compression, this scale also makes it possible to
 /// precompute computationally expensive functions of the fieldnorm
 /// in a very short array.
-#[derive(Clone)]
+pub struct FieldNormReader {
-pub struct FieldNormReader(ReaderImplEnum);
+    data: ReadOnlySource,
-
-impl From<ReaderImplEnum> for FieldNormReader {
-    fn from(reader_enum: ReaderImplEnum) -> FieldNormReader {
-        FieldNormReader(reader_enum)
-    }
-}
-
-#[derive(Clone)]
-enum ReaderImplEnum {
-    FromData(OwnedBytes),
-    Const {
-        num_docs: u32,
-        fieldnorm_id: u8,
-        fieldnorm: u32,
-    },
 }
 
 impl FieldNormReader {
-    /// Creates a `FieldNormReader` with a constant fieldnorm.
+    /// Opens a field norm reader given its data source.
-    ///
+    pub fn open(data: ReadOnlySource) -> Self {
-    /// The fieldnorm will be subjected to compression as if it was coming
+        FieldNormReader { data }
-    /// from an array-backed fieldnorm reader.
-    pub fn constant(num_docs: u32, fieldnorm: u32) -> FieldNormReader {
-        let fieldnorm_id = fieldnorm_to_id(fieldnorm);
-        let fieldnorm = id_to_fieldnorm(fieldnorm_id);
-        ReaderImplEnum::Const {
-            num_docs,
-            fieldnorm_id,
-            fieldnorm,
-        }
-        .into()
-    }
-
-    /// Opens a field norm reader given its file.
-    pub fn open(fieldnorm_file: FileSlice) -> crate::Result<Self> {
-        let data = fieldnorm_file.read_bytes()?;
-        Ok(FieldNormReader::new(data))
-    }
-
-    fn new(data: OwnedBytes) -> Self {
-        ReaderImplEnum::FromData(data).into()
-    }
-
-    /// Returns the number of documents in this segment.
-    pub fn num_docs(&self) -> u32 {
-        match &self.0 {
-            ReaderImplEnum::FromData(data) => data.len() as u32,
-            ReaderImplEnum::Const { num_docs, .. } => *num_docs,
-        }
     }
 
     /// Returns the `fieldnorm` associated to a doc id.
@@ -123,25 +39,15 @@ impl FieldNormReader {
     /// The fieldnorm is effectively decoded from the
     /// `fieldnorm_id` by doing a simple table lookup.
     pub fn fieldnorm(&self, doc_id: DocId) -> u32 {
-        match &self.0 {
+        let fieldnorm_id = self.fieldnorm_id(doc_id);
-            ReaderImplEnum::FromData(data) => {
+        id_to_fieldnorm(fieldnorm_id)
-                let fieldnorm_id = data.as_slice()[doc_id as usize];
-                id_to_fieldnorm(fieldnorm_id)
-            }
-            ReaderImplEnum::Const { fieldnorm, .. } => *fieldnorm,
-        }
     }
 
     /// Returns the `fieldnorm_id` associated to a document.
     #[inline(always)]
     pub fn fieldnorm_id(&self, doc_id: DocId) -> u8 {
-        match &self.0 {
+        let fielnorms_data = self.data.as_slice();
-            ReaderImplEnum::FromData(data) => {
+        fielnorms_data[doc_id as usize]
-                let fieldnorm_id = data.as_slice()[doc_id as usize];
-                fieldnorm_id
-            }
-            ReaderImplEnum::Const { fieldnorm_id, .. } => *fieldnorm_id,
-        }
     }
 
     /// Converts a `fieldnorm_id` into a fieldnorm.
@@ -156,48 +62,18 @@ impl FieldNormReader {
     pub fn fieldnorm_to_id(fieldnorm: u32) -> u8 {
         fieldnorm_to_id(fieldnorm)
     }
-
-    #[cfg(test)]
-    pub fn for_test(field_norms: &[u32]) -> FieldNormReader {
-        let field_norms_id = field_norms
-            .iter()
-            .cloned()
-            .map(FieldNormReader::fieldnorm_to_id)
-            .collect::<Vec<u8>>();
-        let field_norms_data = OwnedBytes::new(field_norms_id);
-        FieldNormReader::new(field_norms_data)
-    }
 }
 
 #[cfg(test)]
-mod tests {
+impl From<Vec<u32>> for FieldNormReader {
-    use crate::fieldnorm::FieldNormReader;
+    fn from(field_norms: Vec<u32>) -> FieldNormReader {
-
+        let field_norms_id = field_norms
-    #[test]
+            .into_iter()
-    fn test_from_fieldnorms_array() {
+            .map(FieldNormReader::fieldnorm_to_id)
-        let fieldnorms = &[1, 2, 3, 4, 1_000_000];
+            .collect::<Vec<u8>>();
-        let fieldnorm_reader = FieldNormReader::for_test(fieldnorms);
+        let field_norms_data = ReadOnlySource::from(field_norms_id);
-        assert_eq!(fieldnorm_reader.num_docs(), 5);
+        FieldNormReader {
-        assert_eq!(fieldnorm_reader.fieldnorm(0), 1);
+            data: field_norms_data,
-        assert_eq!(fieldnorm_reader.fieldnorm(1), 2);
+        }
-        assert_eq!(fieldnorm_reader.fieldnorm(2), 3);
-        assert_eq!(fieldnorm_reader.fieldnorm(3), 4);
-        assert_eq!(fieldnorm_reader.fieldnorm(4), 983_064);
-    }
-
-    #[test]
-    fn test_const_fieldnorm_reader_small_fieldnorm_id() {
-        let fieldnorm_reader = FieldNormReader::constant(1_000_000u32, 10u32);
-        assert_eq!(fieldnorm_reader.num_docs(), 1_000_000u32);
-        assert_eq!(fieldnorm_reader.fieldnorm(0u32), 10u32);
-        assert_eq!(fieldnorm_reader.fieldnorm_id(0u32), 10u8);
-    }
-
-    #[test]
-    fn test_const_fieldnorm_reader_large_fieldnorm_id() {
-        let fieldnorm_reader = FieldNormReader::constant(1_000_000u32, 300u32);
-        assert_eq!(fieldnorm_reader.num_docs(), 1_000_000u32);
-        assert_eq!(fieldnorm_reader.fieldnorm(0u32), 280u32);
-        assert_eq!(fieldnorm_reader.fieldnorm_id(0u32), 72u8);
     }
 }

src/fieldnorm/writer.rs

@@ -4,7 +4,7 @@ use super::fieldnorm_to_id;
 use super::FieldNormsSerializer;
 use crate::schema::Field;
 use crate::schema::Schema;
-use std::{io, iter};
+use std::io;
 
 /// The `FieldNormsWriter` is in charge of tracking the fieldnorm byte
 /// of each document for each field with field norms.
@@ -44,9 +44,7 @@ impl FieldNormsWriter {
             .unwrap_or(0);
         FieldNormsWriter {
             fields,
-            fieldnorms_buffer: iter::repeat_with(Vec::new)
+            fieldnorms_buffer: (0..max_field).map(|_| Vec::new()).collect::<Vec<_>>(),
-                .take(max_field)
-                .collect::<Vec<_>>(),
         }
     }
 
@@ -80,12 +78,11 @@ impl FieldNormsWriter {
     }
 
     /// Serialize the seen fieldnorm values to the serializer for all fields.
-    pub fn serialize(&self, mut fieldnorms_serializer: FieldNormsSerializer) -> io::Result<()> {
+    pub fn serialize(&self, fieldnorms_serializer: &mut FieldNormsSerializer) -> io::Result<()> {
         for &field in self.fields.iter() {
             let fieldnorm_values: &[u8] = &self.fieldnorms_buffer[field.field_id() as usize][..];
             fieldnorms_serializer.serialize_field(field, fieldnorm_values)?;
         }
-        fieldnorms_serializer.close()?;
         Ok(())
     }
 }

src/functional_test.rs

@@ -1,94 +1,45 @@
-use crate::Index;
-use crate::Searcher;
-use crate::{doc, schema::*};
 use rand::thread_rng;
-use rand::Rng;
 use std::collections::HashSet;
 
-fn check_index_content(searcher: &Searcher, vals: &[u64]) -> crate::Result<()> {
+use crate::schema::*;
+use crate::Index;
+use crate::Searcher;
+use rand::Rng;
+
+fn check_index_content(searcher: &Searcher, vals: &HashSet<u64>) {
     assert!(searcher.segment_readers().len() < 20);
     assert_eq!(searcher.num_docs() as usize, vals.len());
-    for segment_reader in searcher.segment_readers() {
-        let store_reader = segment_reader.get_store_reader()?;
-        for doc_id in 0..segment_reader.max_doc() {
-            let _doc = store_reader.get(doc_id)?;
-        }
-    }
-    Ok(())
 }
 
 #[test]
 #[ignore]
-fn test_functional_store() -> crate::Result<()> {
+fn test_indexing() {
-    env_logger::init();
-    let mut schema_builder = Schema::builder();
-
-    let id_field = schema_builder.add_u64_field("id", INDEXED | STORED);
-    let schema = schema_builder.build();
-
-    let index = Index::create_in_ram(schema);
-    let reader = index.reader()?;
-
-    let mut rng = thread_rng();
-
-    let mut index_writer = index.writer_with_num_threads(3, 12_000_000)?;
-
-    let mut doc_set: Vec<u64> = Vec::new();
-
-    let mut doc_id = 0u64;
-    for iteration in 0.. {
-        let num_docs: usize = rng.gen_range(0..4);
-        if doc_set.len() >= 1 {
-            let doc_to_remove_id = rng.gen_range(0..doc_set.len());
-            let removed_doc_id = doc_set.swap_remove(doc_to_remove_id);
-            index_writer.delete_term(Term::from_field_u64(id_field, removed_doc_id));
-        }
-        for _ in 0..num_docs {
-            doc_set.push(doc_id);
-            index_writer.add_document(doc!(id_field=>doc_id));
-            doc_id += 1;
-        }
-        index_writer.commit()?;
-        reader.reload()?;
-        let searcher = reader.searcher();
-        println!("#{} - {}", iteration, searcher.segment_readers().len());
-        check_index_content(&searcher, &doc_set)?;
-    }
-    Ok(())
-}
-
-#[test]
-#[ignore]
-fn test_functional_indexing() -> crate::Result<()> {
     let mut schema_builder = Schema::builder();
 
     let id_field = schema_builder.add_u64_field("id", INDEXED);
     let multiples_field = schema_builder.add_u64_field("multiples", INDEXED);
     let schema = schema_builder.build();
 
-    let index = Index::create_from_tempdir(schema)?;
+    let index = Index::create_from_tempdir(schema).unwrap();
-    let reader = index.reader()?;
+    let reader = index.reader().unwrap();
 
     let mut rng = thread_rng();
 
-    let mut index_writer = index.writer_with_num_threads(3, 120_000_000)?;
+    let mut index_writer = index.writer_with_num_threads(3, 120_000_000).unwrap();
 
     let mut committed_docs: HashSet<u64> = HashSet::new();
     let mut uncommitted_docs: HashSet<u64> = HashSet::new();
 
     for _ in 0..200 {
-        let random_val = rng.gen_range(0..20);
+        let random_val = rng.gen_range(0, 20);
         if random_val == 0 {
-            index_writer.commit()?;
+            index_writer.commit().expect("Commit failed");
             committed_docs.extend(&uncommitted_docs);
             uncommitted_docs.clear();
-            reader.reload()?;
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             // check that everything is correct.
-            check_index_content(
+            check_index_content(&searcher, &committed_docs);
-                &searcher,
-                &committed_docs.iter().cloned().collect::<Vec<u64>>(),
-            )?;
         } else {
             if committed_docs.remove(&random_val) || uncommitted_docs.remove(&random_val) {
                 let doc_id_term = Term::from_field_u64(id_field, random_val);
@@ -104,5 +55,4 @@ fn test_functional_indexing() -> crate::Result<()> {
             }
         }
     }
-    Ok(())
 }

src/indexer/delete_queue.rs

@@ -53,7 +53,7 @@ impl DeleteQueue {
             return block;
         }
         let block = Arc::new(Block {
-            operations: Arc::new([]),
+            operations: Arc::default(),
             next: NextBlock::from(self.clone()),
         });
         wlock.last_block = Arc::downgrade(&block);
@@ -108,7 +108,7 @@ impl DeleteQueue {
         let delete_operations = mem::replace(&mut self_wlock.writer, vec![]);
 
         let new_block = Arc::new(Block {
-            operations: Arc::from(delete_operations.into_boxed_slice()),
+            operations: Arc::new(delete_operations.into_boxed_slice()),
             next: NextBlock::from(self.clone()),
         });
 
@@ -167,7 +167,7 @@ impl NextBlock {
 }
 
 struct Block {
-    operations: Arc<[DeleteOperation]>,
+    operations: Arc<Box<[DeleteOperation]>>,
     next: NextBlock,
 }
 

src/indexer/index_writer.rs

@@ -8,22 +8,26 @@ use crate::core::SegmentComponent;
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::core::SegmentReader;
-use crate::directory::TerminatingWrite;
 use crate::directory::{DirectoryLock, GarbageCollectionResult};
-use crate::docset::{DocSet, TERMINATED};
+use crate::directory::{TerminatingWrite, WatchCallbackList};
+use crate::docset::DocSet;
 use crate::error::TantivyError;
 use crate::fastfield::write_delete_bitset;
 use crate::indexer::delete_queue::{DeleteCursor, DeleteQueue};
 use crate::indexer::doc_opstamp_mapping::DocToOpstampMapping;
 use crate::indexer::operation::DeleteOperation;
+use crate::indexer::segment_manager::SegmentRegisters;
+use crate::indexer::segment_register::SegmentRegister;
 use crate::indexer::stamper::Stamper;
-use crate::indexer::MergePolicy;
+use crate::indexer::{SegmentEntry, ResourceManager};
-use crate::indexer::SegmentEntry;
 use crate::indexer::SegmentWriter;
+use crate::indexer::{IndexWriterConfig, MergePolicy};
+use crate::reader::NRTReader;
 use crate::schema::Document;
 use crate::schema::IndexRecordOption;
 use crate::schema::Term;
-use crate::Opstamp;
+use crate::tokenizer::TokenizerManager;
+use crate::{IndexReader, Opstamp};
 use crossbeam::channel;
 use futures::executor::block_on;
 use futures::future::Future;
@@ -31,18 +35,10 @@ use smallvec::smallvec;
 use smallvec::SmallVec;
 use std::mem;
 use std::ops::Range;
-use std::sync::Arc;
+use std::sync::{Arc, RwLock};
 use std::thread;
 use std::thread::JoinHandle;
 
-// Size of the margin for the heap. A segment is closed when the remaining memory
-// in the heap goes below MARGIN_IN_BYTES.
-pub const MARGIN_IN_BYTES: usize = 1_000_000;
-
-// We impose the memory per thread to be at least 3 MB.
-pub const HEAP_SIZE_MIN: usize = ((MARGIN_IN_BYTES as u32) * 3u32) as usize;
-pub const HEAP_SIZE_MAX: usize = u32::max_value() as usize - MARGIN_IN_BYTES;
-
 // Add document will block if the number of docs waiting in the queue to be indexed
 // reaches `PIPELINE_MAX_SIZE_IN_DOCS`
 const PIPELINE_MAX_SIZE_IN_DOCS: usize = 10_000;
@@ -69,8 +65,9 @@ pub struct IndexWriter {
     _directory_lock: Option<DirectoryLock>,
 
     index: Index,
+    config: IndexWriterConfig,
 
-    heap_size_in_bytes_per_thread: usize,
+    segment_registers: Arc<RwLock<SegmentRegisters>>,
 
     workers_join_handle: Vec<JoinHandle<crate::Result<()>>>,
 
@@ -80,13 +77,14 @@ pub struct IndexWriter {
     segment_updater: SegmentUpdater,
 
     worker_id: usize,
-
-    num_threads: usize,
-
     delete_queue: DeleteQueue,
 
     stamper: Stamper,
     committed_opstamp: Opstamp,
+
+    on_commit: WatchCallbackList,
+
+    memory_manager: ResourceManager,
 }
 
 fn compute_deleted_bitset(
@@ -108,19 +106,19 @@ fn compute_deleted_bitset(
         // Limit doc helps identify the first document
         // that may be affected by the delete operation.
         let limit_doc = doc_opstamps.compute_doc_limit(delete_op.opstamp);
-        let inverted_index = segment_reader.inverted_index(delete_op.term.field())?;
+        let inverted_index = segment_reader.inverted_index(delete_op.term.field());
         if let Some(mut docset) =
-            inverted_index.read_postings(&delete_op.term, IndexRecordOption::Basic)?
+            inverted_index.read_postings(&delete_op.term, IndexRecordOption::Basic)
         {
-            let mut deleted_doc = docset.doc();
+            while docset.advance() {
-            while deleted_doc != TERMINATED {
+                let deleted_doc = docset.doc();
                 if deleted_doc < limit_doc {
                     delete_bitset.insert(deleted_doc);
                     might_have_changed = true;
                 }
-                deleted_doc = docset.advance();
             }
         }
+
         delete_cursor.advance();
     }
     Ok(might_have_changed)
@@ -133,7 +131,6 @@ fn compute_deleted_bitset(
 /// For instance, there was no delete operation between the state of the `segment_entry` and
 /// the `target_opstamp`, `segment_entry` is not updated.
 pub(crate) fn advance_deletes(
-    mut segment: Segment,
     segment_entry: &mut SegmentEntry,
     target_opstamp: Opstamp,
 ) -> crate::Result<()> {
@@ -142,25 +139,33 @@ pub(crate) fn advance_deletes(
         return Ok(());
     }
 
-    if segment_entry.delete_bitset().is_none() && segment_entry.delete_cursor().get().is_none() {
+    let delete_bitset_opt = segment_entry.take_delete_bitset();
+
+    // We avoid directly advancing the `SegmentEntry` delete cursor, because
+    // we do not want to end up in an invalid state if the delete bitset
+    // serialization fails.
+    let mut delete_cursor = segment_entry.delete_cursor();
+
+    if delete_bitset_opt.is_none() && segment_entry.delete_cursor().get().is_none() {
         // There has been no `DeleteOperation` between the segment status and `target_opstamp`.
         return Ok(());
     }
 
+    // We open our current serialized segment to compute the new deleted bitset.
+    let segment = segment_entry.segment().clone();
     let segment_reader = SegmentReader::open(&segment)?;
 
     let max_doc = segment_reader.max_doc();
-    let mut delete_bitset: BitSet = match segment_entry.delete_bitset() {
+
-        Some(previous_delete_bitset) => (*previous_delete_bitset).clone(),
+    let mut delete_bitset: BitSet =
-        None => BitSet::with_max_value(max_doc),
+        delete_bitset_opt.unwrap_or_else(|| BitSet::with_max_value(max_doc));
-    };
 
     let num_deleted_docs_before = segment.meta().num_deleted_docs();
 
     compute_deleted_bitset(
         &mut delete_bitset,
         &segment_reader,
-        segment_entry.delete_cursor(),
+        &mut delete_cursor,
         &DocToOpstampMapping::None,
         target_opstamp,
     )?;
@@ -179,32 +184,40 @@ pub(crate) fn advance_deletes(
     let num_deleted_docs: u32 = delete_bitset.len() as u32;
     if num_deleted_docs > num_deleted_docs_before {
         // There are new deletes. We need to write a new delete file.
-        segment = segment.with_delete_meta(num_deleted_docs as u32, target_opstamp);
+        let mut delete_file = segment
-        let mut delete_file = segment.open_write(SegmentComponent::DELETE)?;
+            .with_delete_meta(num_deleted_docs as u32, target_opstamp)
+            .open_write(SegmentComponent::DELETE)?;
         write_delete_bitset(&delete_bitset, max_doc, &mut delete_file)?;
         delete_file.terminate()?;
+        segment_entry.reset_delete_meta(num_deleted_docs as u32, target_opstamp);
     }
 
-    segment_entry.set_meta(segment.meta().clone());
+    // Regardless of whether we did end up having to write a new file or not
+    // we advance the `delete_cursor`. This is an optimisation. We want to ensure we do not
+    // check that a given deleted term does not match any of our docs more than once.
+    segment_entry.set_delete_cursor(delete_cursor);
     Ok(())
 }
 
 fn index_documents(
-    memory_budget: usize,
+    config: IndexWriterConfig,
     segment: Segment,
     grouped_document_iterator: &mut dyn Iterator<Item = OperationGroup>,
     segment_updater: &mut SegmentUpdater,
+    tokenizers: &TokenizerManager,
     mut delete_cursor: DeleteCursor,
+    memory_manager: ResourceManager
 ) -> crate::Result<bool> {
     let schema = segment.schema();
 
-    let mut segment_writer = SegmentWriter::for_segment(memory_budget, segment.clone(), &schema)?;
+    let mut segment_writer = SegmentWriter::for_segment(
+        &config, segment, &schema, tokenizers, memory_manager)?;
     for document_group in grouped_document_iterator {
         for doc in document_group {
             segment_writer.add_document(doc, &schema)?;
         }
         let mem_usage = segment_writer.mem_usage();
-        if mem_usage >= memory_budget - MARGIN_IN_BYTES {
+        if mem_usage >= config.heap_size_before_flushing() {
             info!(
                 "Buffer limit reached, flushing segment with maxdoc={}.",
                 segment_writer.max_doc()
@@ -223,24 +236,14 @@ fn index_documents(
     // the worker thread.
     assert!(max_doc > 0);
 
-    let doc_opstamps: Vec<Opstamp> = segment_writer.finalize()?;
+    let (segment, doc_opstamps): (Segment, Vec<Opstamp>) = segment_writer.finalize()?;
-
-    let segment_with_max_doc = segment.with_max_doc(max_doc);
 
     let last_docstamp: Opstamp = *(doc_opstamps.last().unwrap());
 
-    let delete_bitset_opt = apply_deletes(
+    let delete_bitset_opt =
-        &segment_with_max_doc,
+        apply_deletes(&segment, &mut delete_cursor, &doc_opstamps, last_docstamp)?;
-        &mut delete_cursor,
-        &doc_opstamps,
-        last_docstamp,
-    )?;
 
-    let segment_entry = SegmentEntry::new(
+    let segment_entry = SegmentEntry::new(segment, delete_cursor, delete_bitset_opt);
-        segment_with_max_doc.meta().clone(),
-        delete_cursor,
-        delete_bitset_opt,
-    );
     block_on(segment_updater.schedule_add_segment(segment_entry))?;
     Ok(true)
 }
@@ -292,21 +295,10 @@ impl IndexWriter {
     /// If the heap size per thread is too small, panics.
     pub(crate) fn new(
         index: &Index,
-        num_threads: usize,
+        mut config: IndexWriterConfig,
-        heap_size_in_bytes_per_thread: usize,
         directory_lock: DirectoryLock,
     ) -> crate::Result<IndexWriter> {
-        if heap_size_in_bytes_per_thread < HEAP_SIZE_MIN {
+        config.validate()?;
-            let err_msg = format!(
-                "The heap size per thread needs to be at least {}.",
-                HEAP_SIZE_MIN
-            );
-            return Err(TantivyError::InvalidArgument(err_msg));
-        }
-        if heap_size_in_bytes_per_thread >= HEAP_SIZE_MAX {
-            let err_msg = format!("The heap size per thread cannot exceed {}", HEAP_SIZE_MAX);
-            return Err(TantivyError::InvalidArgument(err_msg));
-        }
         let (document_sender, document_receiver): (OperationSender, OperationReceiver) =
             channel::bounded(PIPELINE_MAX_SIZE_IN_DOCS);
 
@@ -314,16 +306,26 @@ impl IndexWriter {
 
         let current_opstamp = index.load_metas()?.opstamp;
 
+        let meta = index.load_metas()?;
+
         let stamper = Stamper::new(current_opstamp);
 
+        let commited_segments = SegmentRegister::new(
+            index.directory(),
+            &index.schema(),
+            meta.segments,
+            &delete_queue.cursor(),
+        );
+        let segment_registers = Arc::new(RwLock::new(SegmentRegisters::new(commited_segments)));
+
         let segment_updater =
-            SegmentUpdater::create(index.clone(), stamper.clone(), &delete_queue.cursor())?;
+            SegmentUpdater::create(segment_registers.clone(), index.clone(), stamper.clone())?;
 
         let mut index_writer = IndexWriter {
             _directory_lock: Some(directory_lock),
 
-            heap_size_in_bytes_per_thread,
             index: index.clone(),
+            config,
 
             operation_receiver: document_receiver,
             operation_sender: document_sender,
@@ -331,7 +333,6 @@ impl IndexWriter {
             segment_updater,
 
             workers_join_handle: vec![],
-            num_threads,
 
             delete_queue,
 
@@ -339,6 +340,10 @@ impl IndexWriter {
             stamper,
 
             worker_id: 0,
+            segment_registers,
+            on_commit: Default::default(),
+
+            memory_manager: Default::default()
         };
         index_writer.start_workers()?;
         Ok(index_writer)
@@ -346,7 +351,7 @@ impl IndexWriter {
 
     fn drop_sender(&mut self) {
         let (sender, _receiver) = channel::bounded(1);
-        self.operation_sender = sender;
+        mem::replace(&mut self.operation_sender, sender);
     }
 
     /// If there are some merging threads, blocks until they all finish their work and
@@ -366,23 +371,11 @@ impl IndexWriter {
                 })?;
         }
 
-        let result = self
+        self
             .segment_updater
-            .wait_merging_thread()
+            .wait_merging_thread();
-            .map_err(|_| TantivyError::ErrorInThread("Failed to join merging thread.".into()));
 
-        if let Err(ref e) = result {
+        Ok(())
-            error!("Some merging thread failed {:?}", e);
-        }
-
-        result
-    }
-
-    #[doc(hidden)]
-    pub fn add_segment(&self, segment_meta: SegmentMeta) -> crate::Result<()> {
-        let delete_cursor = self.delete_queue.cursor();
-        let segment_entry = SegmentEntry::new(segment_meta, delete_cursor, None);
-        block_on(self.segment_updater.schedule_add_segment(segment_entry))
     }
 
     /// Creates a new segment.
@@ -405,8 +398,9 @@ impl IndexWriter {
 
         let mut delete_cursor = self.delete_queue.cursor();
 
-        let mem_budget = self.heap_size_in_bytes_per_thread;
         let index = self.index.clone();
+        let config = self.config.clone();
+        let memory_manager = self.memory_manager.clone();
         let join_handle: JoinHandle<crate::Result<()>> = thread::Builder::new()
             .name(format!("thrd-tantivy-index{}", self.worker_id))
             .spawn(move || {
@@ -435,11 +429,13 @@ impl IndexWriter {
                     }
                     let segment = index.new_segment();
                     index_documents(
-                        mem_budget,
+                        config.clone(),
                         segment,
                         &mut document_iterator,
                         &mut segment_updater,
+                        index.tokenizers(),
                         delete_cursor.clone(),
+                        memory_manager.clone()
                     )?;
                 }
             })?;
@@ -449,7 +445,7 @@ impl IndexWriter {
     }
 
     /// Accessor to the merge policy.
-    pub fn get_merge_policy(&self) -> Arc<dyn MergePolicy> {
+    pub fn get_merge_policy(&self) -> Arc<Box<dyn MergePolicy>> {
         self.segment_updater.get_merge_policy()
     }
 
@@ -459,7 +455,7 @@ impl IndexWriter {
     }
 
     fn start_workers(&mut self) -> crate::Result<()> {
-        for _ in 0..self.num_threads {
+        for _ in 0..self.config.max_indexing_threads {
             self.add_indexing_worker()?;
         }
         Ok(())
@@ -536,7 +532,6 @@ impl IndexWriter {
     /// when no documents are remaining.
     ///
     /// Returns the former segment_ready channel.
-    #[allow(unused_must_use)]
     fn recreate_document_channel(&mut self) -> OperationReceiver {
         let (document_sender, document_receiver): (OperationSender, OperationReceiver) =
             channel::bounded(PIPELINE_MAX_SIZE_IN_DOCS);
@@ -565,18 +560,14 @@ impl IndexWriter {
             .take()
             .expect("The IndexWriter does not have any lock. This is a bug, please report.");
 
-        let new_index_writer: IndexWriter = IndexWriter::new(
+        let new_index_writer: IndexWriter =
-            &self.index,
+            IndexWriter::new(&self.index, self.config.clone(), directory_lock)?;
-            self.num_threads,
-            self.heap_size_in_bytes_per_thread,
-            directory_lock,
-        )?;
 
         // the current `self` is dropped right away because of this call.
         //
         // This will drop the document queue, and the thread
         // should terminate.
-        *self = new_index_writer;
+        mem::replace(self, new_index_writer);
 
         // Drains the document receiver pipeline :
         // Workers don't need to index the pending documents.
@@ -609,7 +600,7 @@ impl IndexWriter {
     /// It is also possible to add a payload to the `commit`
     /// using this API.
     /// See [`PreparedCommit::set_payload()`](PreparedCommit.html)
-    pub fn prepare_commit(&mut self) -> crate::Result<PreparedCommit> {
+    pub fn prepare_commit(&mut self, soft_commit: bool) -> crate::Result<PreparedCommit> {
         // Here, because we join all of the worker threads,
         // all of the segment update for this commit have been
         // sent.
@@ -637,7 +628,7 @@ impl IndexWriter {
         }
 
         let commit_opstamp = self.stamper.stamp();
-        let prepared_commit = PreparedCommit::new(self, commit_opstamp);
+        let prepared_commit = PreparedCommit::new(self, commit_opstamp, soft_commit);
         info!("Prepared commit {}", commit_opstamp);
         Ok(prepared_commit)
     }
@@ -657,7 +648,25 @@ impl IndexWriter {
     /// that made it in the commit.
     ///
     pub fn commit(&mut self) -> crate::Result<Opstamp> {
-        self.prepare_commit()?.commit()
+        self.prepare_commit(false)?.commit()
+    }
+
+    pub fn soft_commit(&mut self) -> crate::Result<Opstamp> {
+        self.prepare_commit(true)?.commit()
+    }
+
+    pub(crate) fn trigger_commit(&self) -> impl Future<Output = ()> {
+        self.on_commit.broadcast()
+    }
+
+    pub fn reader(&self, num_searchers: usize) -> crate::Result<IndexReader> {
+        let nrt_reader = NRTReader::create(
+            num_searchers,
+            self.index.clone(),
+            self.segment_registers.clone(),
+            &self.on_commit,
+        )?;
+        Ok(IndexReader::NRT(nrt_reader))
     }
 
     pub(crate) fn segment_updater(&self) -> &SegmentUpdater {
@@ -800,7 +809,7 @@ mod tests {
         let mut schema_builder = schema::Schema::builder();
         let text_field = schema_builder.add_text_field("text", schema::TEXT);
         let index = Index::create_in_ram(schema_builder.build());
-        let index_writer = index.writer_for_tests().unwrap();
+        let index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let operations = vec![
             UserOperation::Add(doc!(text_field=>"a")),
             UserOperation::Add(doc!(text_field=>"b")),
@@ -815,7 +824,7 @@ mod tests {
         let text_field = schema_builder.add_text_field("text", schema::TEXT);
         let index = Index::create_in_ram(schema_builder.build());
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(text_field => "hello1"));
         index_writer.add_document(doc!(text_field => "hello2"));
         assert!(index_writer.commit().is_ok());
@@ -864,7 +873,7 @@ mod tests {
             .reload_policy(ReloadPolicy::Manual)
             .try_into()
             .unwrap();
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let a_term = Term::from_field_text(text_field, "a");
         let b_term = Term::from_field_text(text_field, "b");
         let operations = vec![
@@ -926,8 +935,8 @@ mod tests {
     fn test_lockfile_already_exists_error_msg() {
         let schema_builder = schema::Schema::builder();
         let index = Index::create_in_ram(schema_builder.build());
-        let _index_writer = index.writer_for_tests().unwrap();
+        let _index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-        match index.writer_for_tests() {
+        match index.writer_with_num_threads(1, 3_000_000) {
             Err(err) => {
                 let err_msg = err.to_string();
                 assert!(err_msg.contains("already an `IndexWriter`"));
@@ -979,7 +988,7 @@ mod tests {
         let num_docs_containing = |s: &str| {
             let searcher = reader.searcher();
             let term = Term::from_field_text(text_field, s);
-            searcher.doc_freq(&term).unwrap()
+            searcher.doc_freq(&term)
         };
 
         {
@@ -1015,7 +1024,7 @@ mod tests {
             .unwrap();
         let num_docs_containing = |s: &str| {
             let term_a = Term::from_field_text(text_field, s);
-            reader.searcher().doc_freq(&term_a).unwrap()
+            reader.searcher().doc_freq(&term_a)
         };
         {
             // writing the segment
@@ -1055,7 +1064,8 @@ mod tests {
                 index_writer.add_document(doc!(text_field => "a"));
             }
             {
-                let mut prepared_commit = index_writer.prepare_commit().expect("commit failed");
+                let mut prepared_commit =
+                    index_writer.prepare_commit(false).expect("commit failed");
                 prepared_commit.set_payload("first commit");
                 prepared_commit.commit().expect("commit failed");
             }
@@ -1088,7 +1098,8 @@ mod tests {
                 index_writer.add_document(doc!(text_field => "a"));
             }
             {
-                let mut prepared_commit = index_writer.prepare_commit().expect("commit failed");
+                let mut prepared_commit =
+                    index_writer.prepare_commit(false).expect("commit failed");
                 prepared_commit.set_payload("first commit");
                 prepared_commit.abort().expect("commit failed");
             }
@@ -1110,7 +1121,6 @@ mod tests {
                 .unwrap()
                 .searcher()
                 .doc_freq(&term_a)
-                .unwrap()
         };
         assert_eq!(num_docs_containing("a"), 0);
         assert_eq!(num_docs_containing("b"), 100);
@@ -1130,7 +1140,7 @@ mod tests {
             reader.reload().unwrap();
             let searcher = reader.searcher();
             let term = Term::from_field_text(text_field, s);
-            searcher.doc_freq(&term).unwrap()
+            searcher.doc_freq(&term)
         };
         let mut index_writer = index.writer_with_num_threads(4, 12_000_000).unwrap();
 
@@ -1181,15 +1191,7 @@ mod tests {
 
         // working with an empty index == no documents
         let term_b = Term::from_field_text(text_field, "b");
-        assert_eq!(
+        assert_eq!(index.reader().unwrap().searcher().doc_freq(&term_b), 0);
-            index
-                .reader()
-                .unwrap()
-                .searcher()
-                .doc_freq(&term_b)
-                .unwrap(),
-            0
-        );
     }
 
     #[test]
@@ -1209,15 +1211,7 @@ mod tests {
 
         let term_a = Term::from_field_text(text_field, "a");
         // expect the document with that term to be in the index
-        assert_eq!(
+        assert_eq!(index.reader().unwrap().searcher().doc_freq(&term_a), 1);
-            index
-                .reader()
-                .unwrap()
-                .searcher()
-                .doc_freq(&term_a)
-                .unwrap(),
-            1
-        );
     }
 
     #[test]
@@ -1243,15 +1237,7 @@ mod tests {
         // Find original docs in the index
         let term_a = Term::from_field_text(text_field, "a");
         // expect the document with that term to be in the index
-        assert_eq!(
+        assert_eq!(index.reader().unwrap().searcher().doc_freq(&term_a), 1);
-            index
-                .reader()
-                .unwrap()
-                .searcher()
-                .doc_freq(&term_a)
-                .unwrap(),
-            1
-        );
     }
 
     #[test]
@@ -1286,9 +1272,46 @@ mod tests {
         let idfield = schema_builder.add_text_field("id", STRING);
         schema_builder.add_text_field("optfield", STRING);
         let index = Index::create_in_ram(schema_builder.build());
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(idfield=>"myid"));
         let commit = index_writer.commit();
         assert!(commit.is_ok());
     }
+
+    #[test]
+    fn test_index_writer_reader() {
+        let mut schema_builder = schema::Schema::builder();
+        let idfield = schema_builder.add_text_field("id", STRING);
+        schema_builder.add_text_field("optfield", STRING);
+        let index = Index::create_in_ram(schema_builder.build());
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(idfield=>"myid"));
+        assert!(index_writer.commit().is_ok());
+        let reader = index_writer.reader(2).unwrap();
+        let searcher = reader.searcher();
+        assert_eq!(searcher.num_docs(), 1u64);
+        index_writer.add_document(doc!(idfield=>"myid"));
+        assert!(index_writer.commit().is_ok());
+        assert_eq!(reader.searcher().num_docs(), 2u64);
+        assert_eq!(searcher.num_docs(), 1u64);
+    }
+
+    #[test]
+    fn test_index_writer_reader_soft_commit() {
+        let mut schema_builder = schema::Schema::builder();
+        let idfield = schema_builder.add_text_field("id", STRING);
+        schema_builder.add_text_field("optfield", STRING);
+        let index = Index::create_in_ram(schema_builder.build());
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(idfield=>"myid"));
+        assert!(index_writer.soft_commit().is_ok());
+        let nrt_reader = index_writer.reader(2).unwrap();
+        let normal_reader = index.reader_builder().try_into().unwrap();
+        assert_eq!(nrt_reader.searcher().num_docs(), 1u64);
+        assert_eq!(normal_reader.searcher().num_docs(), 0u64);
+        assert!(index_writer.commit().is_ok());
+        assert!(normal_reader.reload().is_ok());
+        assert_eq!(nrt_reader.searcher().num_docs(), 1u64);
+        assert_eq!(normal_reader.searcher().num_docs(), 1u64);
+    }
 }

src/indexer/index_writer_config.rs

@@ -0,0 +1,133 @@
+use serde::{Deserialize, Serialize};
+
+// Size of the margin for the heap. A segment is closed when the remaining memory
+// in the heap goes below MARGIN_IN_BYTES.
+const MARGIN_IN_BYTES: u64 = 1_000_000;
+
+// We impose the memory per thread to be at least 3 MB.
+const HEAP_SIZE_MIN: u64 = MARGIN_IN_BYTES * 3u64;
+const HEAP_SIZE_MAX: u64 = u32::max_value() as u64 - MARGIN_IN_BYTES;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct IndexWriterConfig {
+    pub max_indexing_threads: usize,
+    pub max_merging_threads: usize,
+    pub memory_budget: u64,
+    pub store_flush_num_bytes: u64,
+    pub persist_low: u64,
+    pub persist_high: u64,
+}
+
+impl Default for IndexWriterConfig {
+    fn default() -> Self {
+        IndexWriterConfig {
+            max_indexing_threads: 1,
+            max_merging_threads: 3,
+            memory_budget: 50_000_000u64,
+            store_flush_num_bytes: 10_000_000u64,
+            persist_low: 10_000_000u64,
+            persist_high: 50_000_000u64
+        }
+    }
+}
+
+impl IndexWriterConfig {
+    #[cfg(test)]
+    pub fn for_test() -> IndexWriterConfig {
+        IndexWriterConfig {
+            max_indexing_threads: 1,
+            max_merging_threads: 5,
+            memory_budget: 4_000_000u64,
+            store_flush_num_bytes: 500_000u64,
+            persist_low: 2_000_000u64,
+            persist_high: 3_000_000u64,
+        }
+    }
+
+    // Ensures the `IndexWriterConfig` is correct.
+    //
+    // This method checks that the values in the `IndexWriterConfig`
+    // are valid. If it is not, it may mutate some of the values (like `max_num_threads`) to
+    // fit the contracts or return an error with an explicit error message.
+    //
+    // If called twice, the config is guaranteed to not be updated the second time.
+    pub fn validate(&mut self) -> crate::Result<()> {
+        if self.memory_budget < HEAP_SIZE_MIN {
+            let err_msg = format!(
+                "The heap size per thread needs to be at least {}.",
+                HEAP_SIZE_MIN
+            );
+            return Err(crate::TantivyError::InvalidArgument(err_msg));
+        }
+        let heap_size_in_bytes_per_thread = self.heap_size_in_byte_per_thread();
+        if heap_size_in_bytes_per_thread >= HEAP_SIZE_MAX {
+            let err_msg = format!("The heap size per thread cannot exceed {}", HEAP_SIZE_MAX);
+            return Err(crate::TantivyError::InvalidArgument(err_msg));
+        }
+        if heap_size_in_bytes_per_thread < HEAP_SIZE_MIN {
+            self.max_indexing_threads = (self.memory_budget / HEAP_SIZE_MIN) as usize;
+        }
+        Ok(())
+    }
+
+    pub fn heap_size_in_byte_per_thread(&self) -> u64 {
+        self.memory_budget / self.max_indexing_threads as u64
+    }
+
+    pub fn heap_size_before_flushing(&self) -> u64 {
+        self.heap_size_in_byte_per_thread() - MARGIN_IN_BYTES
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::IndexWriterConfig;
+
+    #[test]
+    fn test_index_writer_config_simple() {
+        let mut index = IndexWriterConfig {
+            max_indexing_threads: 3,
+            memory_budget: super::HEAP_SIZE_MIN * 3,
+            ..Default::default()
+        };
+        assert!(index.validate().is_ok());
+        assert_eq!(index.max_indexing_threads, 3);
+        assert_eq!(index.heap_size_in_byte_per_thread(), super::HEAP_SIZE_MIN);
+    }
+
+    #[test]
+    fn test_index_writer_config_reduce_num_threads() {
+        let mut index = IndexWriterConfig {
+            max_indexing_threads: 3,
+            memory_budget: super::HEAP_SIZE_MIN,
+            ..Default::default()
+        };
+        assert!(index.validate().is_ok());
+        assert_eq!(index.max_indexing_threads, 1);
+        assert_eq!(index.heap_size_in_byte_per_thread(), super::HEAP_SIZE_MIN);
+    }
+
+    #[test]
+    fn test_index_writer_config_not_enough_memory() {
+        let mut index = IndexWriterConfig {
+            max_indexing_threads: 1,
+            memory_budget: super::HEAP_SIZE_MIN - 1,
+            ..Default::default()
+        };
+        assert!(
+            matches!(index.validate(), Err(crate::TantivyError::InvalidArgument(msg) ) if msg.contains("The heap size per thread needs to be at least"))
+        );
+    }
+
+    #[test]
+    fn test_index_writer_config_too_much_memory() {
+        let mut index = IndexWriterConfig {
+            max_indexing_threads: 1,
+            memory_budget: (u32::max_value() as u64) + 1,
+            ..Default::default()
+        };
+        assert!(
+            matches!(index.validate(), Err(crate::TantivyError::InvalidArgument(msg) ) if msg.contains("The heap size per thread cannot exceed"))
+        );
+    }
+}

src/indexer/log_merge_policy.rs

@@ -8,7 +8,7 @@ const DEFAULT_MIN_LAYER_SIZE: u32 = 10_000;
 const DEFAULT_MIN_MERGE_SIZE: usize = 8;
 const DEFAULT_MAX_MERGE_SIZE: usize = 10_000_000;
 
-/// `LogMergePolicy` tries to merge segments that have a similar number of
+/// `LogMergePolicy` tries tries to merge segments that have a similar number of
 /// documents.
 #[derive(Debug, Clone)]
 pub struct LogMergePolicy {
@@ -54,6 +54,10 @@ impl LogMergePolicy {
 
 impl MergePolicy for LogMergePolicy {
     fn compute_merge_candidates(&self, segments: &[SegmentMeta]) -> Vec<MergeCandidate> {
+        if segments.is_empty() {
+            return Vec::new();
+        }
+
         let mut size_sorted_tuples = segments
             .iter()
             .map(SegmentMeta::num_docs)
@@ -63,35 +67,27 @@ impl MergePolicy for LogMergePolicy {
 
         size_sorted_tuples.sort_by(|x, y| y.1.cmp(&(x.1)));
 
-        if size_sorted_tuples.len() <= 1 {
-            return Vec::new();
-        }
-
         let size_sorted_log_tuples: Vec<_> = size_sorted_tuples
             .into_iter()
             .map(|(ind, num_docs)| (ind, f64::from(self.clip_min_size(num_docs)).log2()))
             .collect();
 
-        if let Some(&(first_ind, first_score)) = size_sorted_log_tuples.first() {
+        let (first_ind, first_score) = size_sorted_log_tuples[0];
-            let mut current_max_log_size = first_score;
+        let mut current_max_log_size = first_score;
-            let mut levels = vec![vec![first_ind]];
+        let mut levels = vec![vec![first_ind]];
-            for &(ind, score) in (&size_sorted_log_tuples).iter().skip(1) {
+        for &(ind, score) in (&size_sorted_log_tuples).iter().skip(1) {
-                if score < (current_max_log_size - self.level_log_size) {
+            if score < (current_max_log_size - self.level_log_size) {
-                    current_max_log_size = score;
+                current_max_log_size = score;
-                    levels.push(Vec::new());
+                levels.push(Vec::new());
-                }
-                levels.last_mut().unwrap().push(ind);
             }
-            levels
+            levels.last_mut().unwrap().push(ind);
-                .iter()
-                .filter(|level| level.len() >= self.min_merge_size)
-                .map(|ind_vec| {
-                    MergeCandidate(ind_vec.iter().map(|&ind| segments[ind].id()).collect())
-                })
-                .collect()
-        } else {
-            return vec![];
         }
+
+        levels
+            .iter()
+            .filter(|level| level.len() >= self.min_merge_size)
+            .map(|ind_vec| MergeCandidate(ind_vec.iter().map(|&ind| segments[ind].id()).collect()))
+            .collect()
     }
 }
 
@@ -183,7 +179,6 @@ mod tests {
         let result_list = test_merge_policy().compute_merge_candidates(&test_input);
         assert_eq!(result_list.len(), 2);
     }
-
     #[test]
     fn test_log_merge_policy_small_segments() {
         // segments under min_layer_size are merged together
@@ -199,17 +194,6 @@ mod tests {
         assert_eq!(result_list.len(), 1);
     }
 
-    #[test]
-    fn test_log_merge_policy_all_segments_too_large_to_merge() {
-        let eight_large_segments: Vec<SegmentMeta> =
-            std::iter::repeat_with(|| create_random_segment_meta(100_001))
-                .take(8)
-                .collect();
-        assert!(test_merge_policy()
-            .compute_merge_candidates(&eight_large_segments)
-            .is_empty());
-    }
-
     #[test]
     fn test_large_merge_segments() {
         let test_input = vec![

src/indexer/merge_operation.rs

@@ -1,17 +1,22 @@
+use crate::indexer::resource_manager::{Allocation, ResourceManager};
 use crate::Opstamp;
 use crate::SegmentId;
 use census::{Inventory, TrackedObject};
 use std::collections::HashSet;
+use std::fmt;
 use std::ops::Deref;
 
-#[derive(Default)]
+#[derive(Default, Clone)]
-pub(crate) struct MergeOperationInventory(Inventory<InnerMergeOperation>);
+pub(crate) struct MergeOperationInventory {
+    inventory: Inventory<InnerMergeOperation>,
+    num_merge_watcher: ResourceManager,
+}
 
 impl Deref for MergeOperationInventory {
     type Target = Inventory<InnerMergeOperation>;
 
     fn deref(&self) -> &Self::Target {
-        &self.0
+        &self.inventory
     }
 }
 
@@ -25,6 +30,10 @@ impl MergeOperationInventory {
         }
         segment_in_merge
     }
+
+    pub fn wait_until_empty(&self) {
+        let _ = self.num_merge_watcher.wait_until_in_range(0..1);
+    }
 }
 
 /// A `MergeOperation` has two roles.
@@ -47,6 +56,17 @@ pub struct MergeOperation {
 pub(crate) struct InnerMergeOperation {
     target_opstamp: Opstamp,
     segment_ids: Vec<SegmentId>,
+    _allocation: Allocation,
+}
+
+impl fmt::Debug for InnerMergeOperation {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "MergeOp(target_opstamp={:?}, segment_ids={:?})",
+            self.target_opstamp, self.segment_ids
+        )
+    }
 }
 
 impl MergeOperation {
@@ -55,9 +75,11 @@ impl MergeOperation {
         target_opstamp: Opstamp,
         segment_ids: Vec<SegmentId>,
     ) -> MergeOperation {
+        let allocation = inventory.num_merge_watcher.allocate(1);
         let inner_merge_operation = InnerMergeOperation {
             target_opstamp,
             segment_ids,
+            _allocation: allocation,
         };
         MergeOperation {
             inner: inventory.track(inner_merge_operation),

src/indexer/mod.rs

@@ -2,12 +2,14 @@ pub mod delete_queue;
 
 mod doc_opstamp_mapping;
 pub mod index_writer;
+mod index_writer_config;
 mod log_merge_policy;
 mod merge_operation;
 pub mod merge_policy;
 pub mod merger;
 pub mod operation;
 mod prepared_commit;
+mod resource_manager;
 mod segment_entry;
 mod segment_manager;
 mod segment_register;
@@ -16,22 +18,25 @@ pub mod segment_updater;
 mod segment_writer;
 mod stamper;
 
+pub(crate) use self::resource_manager::{Allocation, ResourceManager};
+pub(crate) use self::merge_operation::MergeOperationInventory;
 pub use self::index_writer::IndexWriter;
+pub use self::index_writer_config::IndexWriterConfig;
 pub use self::log_merge_policy::LogMergePolicy;
 pub use self::merge_operation::MergeOperation;
 pub use self::merge_policy::{MergeCandidate, MergePolicy, NoMergePolicy};
 pub use self::prepared_commit::PreparedCommit;
 pub use self::segment_entry::SegmentEntry;
 pub use self::segment_manager::SegmentManager;
+pub(crate) use self::segment_manager::SegmentRegisters;
 pub use self::segment_serializer::SegmentSerializer;
 pub use self::segment_writer::SegmentWriter;
 
 /// Alias for the default merge policy, which is the `LogMergePolicy`.
 pub type DefaultMergePolicy = LogMergePolicy;
 
-#[cfg(feature = "mmap")]
 #[cfg(test)]
-mod tests_mmap {
+mod tests {
     use crate::schema::{self, Schema};
     use crate::{Index, Term};
 
@@ -40,7 +45,7 @@ mod tests_mmap {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", schema::TEXT);
         let index = Index::create_from_tempdir(schema_builder.build()).unwrap();
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         // there must be one deleted document in the segment
         index_writer.add_document(doc!(text_field=>"b"));
         index_writer.delete_term(Term::from_field_text(text_field, "b"));

src/indexer/operation.rs

@@ -9,15 +9,6 @@ pub struct DeleteOperation {
     pub term: Term,
 }
 
-impl Default for DeleteOperation {
-    fn default() -> Self {
-        DeleteOperation {
-            opstamp: 0u64,
-            term: Term::new(),
-        }
-    }
-}
-
 /// Timestamped Add operation.
 #[derive(Eq, PartialEq, Debug)]
 pub struct AddOperation {

src/indexer/prepared_commit.rs

@@ -7,14 +7,20 @@ pub struct PreparedCommit<'a> {
     index_writer: &'a mut IndexWriter,
     payload: Option<String>,
     opstamp: Opstamp,
+    soft_commit: bool,
 }
 
 impl<'a> PreparedCommit<'a> {
-    pub(crate) fn new(index_writer: &'a mut IndexWriter, opstamp: Opstamp) -> PreparedCommit<'_> {
+    pub(crate) fn new(
+        index_writer: &'a mut IndexWriter,
+        opstamp: Opstamp,
+        soft_commit: bool,
+    ) -> PreparedCommit<'_> {
         PreparedCommit {
             index_writer,
             payload: None,
             opstamp,
+            soft_commit,
         }
     }
 
@@ -32,11 +38,12 @@ impl<'a> PreparedCommit<'a> {
 
     pub fn commit(self) -> crate::Result<Opstamp> {
         info!("committing {}", self.opstamp);
-        let _ = block_on(
+        block_on(self.index_writer.segment_updater().schedule_commit(
-            self.index_writer
+            self.opstamp,
-                .segment_updater()
+            self.payload,
-                .schedule_commit(self.opstamp, self.payload),
+            self.soft_commit,
-        );
+        ))?;
+        block_on(self.index_writer.trigger_commit());
         Ok(self.opstamp)
     }
 }

src/indexer/resource_manager.rs

@@ -0,0 +1,213 @@
+use std::ops::RangeBounds;
+use std::sync::{Arc, Condvar, Mutex, MutexGuard, RwLock};
+
+struct LockedData {
+    count: u64,
+    enabled: bool
+}
+
+impl Default for LockedData {
+    fn default() -> Self {
+        LockedData {
+            count: 0u64,
+            enabled: true
+        }
+    }
+}
+
+#[derive(Default)]
+struct Inner {
+    resource_level: Mutex<LockedData>,
+    convdvar: Condvar,
+}
+
+
+/// The resource manager makes it possible to track the amount of level of a given resource.
+/// There is no magic here : it is to the description of the user to declare how much
+/// of the resource is being held.
+///
+/// Allocation of a resource is bound to the lifetime of a `Allocation` instance.
+///
+/// ```rust
+/// let resource_manager = ResourceManager::default();
+///
+/// ```
+///
+/// In tantivy, this is used to check the number of merging thread and the number of memory
+/// used by the volatile segments.
+///
+#[derive(Clone, Default)]
+pub struct ResourceManager {
+    inner: Arc<Inner>,
+}
+
+impl ResourceManager {
+    /// Return the total amount of reousrce allocated
+    pub fn total_amount(&self) -> u64 {
+        self.lock().count
+    }
+
+    fn lock(&self) -> MutexGuard<LockedData> {
+        self.inner
+            .resource_level
+            .lock()
+            .expect("Failed to obtain lock for ReservedMemory. This should never happen.")
+    }
+
+    fn record_delta(&self, delta: i64) {
+        if delta == 0i64 {
+            return;
+        }
+        let mut lock = self.lock();
+        let new_val = lock.count as i64 + delta;
+        lock.count = new_val as u64;
+        self.inner.convdvar.notify_all();
+    }
+
+    /// Records a new allocation.
+    ///
+    /// The returned allocate object is used to automatically release the allocated resource
+    /// on drop.
+    pub fn allocate(&self, amount: u64) -> Allocation {
+        self.record_delta(amount as i64);
+        Allocation {
+            resource_manager: self.clone(),
+            amount: RwLock::new(amount),
+        }
+    }
+
+    /// Stops the resource manager.
+    ///
+    /// If any thread is waiting via `.wait_until_in_range(...)`, the method will stop
+    /// being blocking and will return an error.
+    pub fn terminate(&self) {
+        self.lock().enabled = false;
+        self.inner.convdvar.notify_all();
+    }
+
+    /// Blocks the current thread until the resource level reaches the given range,
+    /// in a cpu-efficient way.
+    ///
+    /// This method does not necessarily wakes up the current thread at every transition
+    /// into the targetted range, but any durable entry in the range will be detected.
+    pub fn wait_until_in_range<R: RangeBounds<u64>>(&self, range: R) -> Result<u64, u64> {
+        let mut levels = self.lock();
+        if !levels.enabled {
+            return Err(levels.count)
+        }
+        while !range.contains(&levels.count) {
+           levels = self.inner.convdvar.wait(levels).unwrap();
+            if !levels.enabled {
+                return Err(levels.count)
+            }
+        }
+        Ok(levels.count)
+    }
+}
+
+pub struct Allocation {
+    resource_manager: ResourceManager,
+    amount: RwLock<u64>,
+}
+
+impl Allocation {
+    pub fn amount(&self) -> u64 {
+        *self.amount.read().unwrap()
+    }
+
+    pub fn modify(&self, new_amount: u64) {
+        let mut wlock = self.amount.write().unwrap();
+        let delta = new_amount as i64 - *wlock as i64;
+        *wlock = new_amount;
+        self.resource_manager.record_delta(delta);
+    }
+}
+
+impl Drop for Allocation {
+    fn drop(&mut self) {
+        let amount = self.amount();
+        self.resource_manager.record_delta(-(amount as i64))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ResourceManager;
+    use futures::channel::oneshot;
+    use futures::executor::block_on;
+    use std::{mem, thread};
+
+    #[test]
+    fn test_simple_allocation() {
+        let memory = ResourceManager::default();
+        assert_eq!(memory.total_amount(), 0u64);
+        let _allocation = memory.allocate(10u64);
+        assert_eq!(memory.total_amount(), 10u64);
+    }
+
+    #[test]
+    fn test_multiple_allocation() {
+        let memory = ResourceManager::default();
+        assert_eq!(memory.total_amount(), 0u64);
+        let _allocation = memory.allocate(10u64);
+        let _allocation_2 = memory.allocate(11u64);
+        assert_eq!(memory.total_amount(), 21u64);
+    }
+
+    #[test]
+    fn test_release_on_drop() {
+        let memory = ResourceManager::default();
+        assert_eq!(memory.total_amount(), 0u64);
+        let allocation = memory.allocate(10u64);
+        let allocation_2 = memory.allocate(11u64);
+        assert_eq!(memory.total_amount(), 21u64);
+        mem::drop(allocation);
+        assert_eq!(memory.total_amount(), 11u64);
+        mem::drop(allocation_2);
+        assert_eq!(memory.total_amount(), 0u64);
+    }
+
+    #[test]
+    fn test_wait_until() {
+        let memory = ResourceManager::default();
+        let (send, recv) = oneshot::channel::<()>();
+        let memory_clone = memory.clone();
+        thread::spawn(move || {
+            let _allocation1 = memory_clone.allocate(2u64);
+            let _allocation2 = memory_clone.allocate(3u64);
+            let _allocation3 = memory_clone.allocate(4u64);
+            std::mem::drop(_allocation3);
+            assert!(block_on(recv).is_ok());
+        });
+        assert_eq!(memory.wait_until_in_range(5u64..8u64), Ok(5u64));
+        assert!(send.send(()).is_ok());
+    }
+
+    #[test]
+    fn test_modify_amount() {
+        let memory = ResourceManager::default();
+        let alloc = memory.allocate(2u64);
+        assert_eq!(memory.total_amount(), 2u64);
+        assert_eq!(alloc.amount(), 2u64);
+        let alloc2 = memory.allocate(3u64);
+        assert_eq!(memory.total_amount(), 2u64 + 3u64);
+        assert_eq!(alloc2.amount(), 3u64);
+        alloc.modify(14u64);
+        assert_eq!(alloc.amount(), 14u64);
+        assert_eq!(memory.total_amount(), 14u64 + 3u64)
+    }
+    
+    #[test]
+    fn test_stop_resource_manager() {
+        let resource_manager = ResourceManager::default();
+        let resource_manager_clone = resource_manager.clone();
+        let (sender, recv) = oneshot::channel();
+        let join_handle = thread::spawn(move || {
+            assert!(sender.send(()).is_ok());
+            resource_manager_clone.wait_until_in_range(10..20)
+        });
+        let _ = block_on(recv);
+        resource_manager.terminate();
+        assert_eq!(join_handle.join().unwrap(), Err(0u64));
+    }
+}

src/indexer/segment_entry.rs

@@ -1,7 +1,9 @@
 use crate::common::BitSet;
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
+use crate::directory::ManagedDirectory;
 use crate::indexer::delete_queue::DeleteCursor;
+use crate::{Opstamp, Segment};
 use std::fmt;
 
 /// A segment entry describes the state of
@@ -19,7 +21,7 @@ use std::fmt;
 /// in the .del file or in the `delete_bitset`.
 #[derive(Clone)]
 pub struct SegmentEntry {
-    meta: SegmentMeta,
+    segment: Segment,
     delete_bitset: Option<BitSet>,
     delete_cursor: DeleteCursor,
 }
@@ -27,47 +29,67 @@ pub struct SegmentEntry {
 impl SegmentEntry {
     /// Create a new `SegmentEntry`
     pub fn new(
-        segment_meta: SegmentMeta,
+        segment: Segment,
         delete_cursor: DeleteCursor,
         delete_bitset: Option<BitSet>,
     ) -> SegmentEntry {
         SegmentEntry {
-            meta: segment_meta,
+            segment,
             delete_bitset,
             delete_cursor,
         }
     }
 
-    /// Return a reference to the segment entry deleted bitset.
+    pub fn persist(&mut self, dest_directory: ManagedDirectory) -> crate::Result<()> {
-    ///
+        // TODO take in account delete bitset?
-    /// `DocId` in this bitset are flagged as deleted.
+        self.segment.persist(dest_directory)?;
-    pub fn delete_bitset(&self) -> Option<&BitSet> {
+        Ok(())
-        self.delete_bitset.as_ref()
     }
 
-    /// Set the `SegmentMeta` for this segment.
+    pub fn set_delete_cursor(&mut self, delete_cursor: DeleteCursor) {
-    pub fn set_meta(&mut self, segment_meta: SegmentMeta) {
+        self.delete_cursor = delete_cursor;
-        self.meta = segment_meta;
+    }
+
+    /// `Takes` (as in Option::take) the delete bitset of a segment entry.
+    /// `DocId` in this bitset are flagged as deleted.
+    pub fn take_delete_bitset(&mut self) -> Option<BitSet> {
+        self.delete_bitset.take()
+    }
+
+    /// Reset the delete information in this segment.
+    ///
+    /// The `SegmentEntry` segment's `SegmentMeta` gets updated, and
+    /// any delete bitset is drop and set to None.
+    pub fn reset_delete_meta(&mut self, num_deleted_docs: u32, target_opstamp: Opstamp) {
+        self.segment = self
+            .segment
+            .clone()
+            .with_delete_meta(num_deleted_docs, target_opstamp);
+        self.delete_bitset = None;
     }
 
     /// Return a reference to the segment_entry's delete cursor
-    pub fn delete_cursor(&mut self) -> &mut DeleteCursor {
+    pub fn delete_cursor(&mut self) -> DeleteCursor {
-        &mut self.delete_cursor
+        self.delete_cursor.clone()
     }
 
     /// Returns the segment id.
     pub fn segment_id(&self) -> SegmentId {
-        self.meta.id()
+        self.meta().id()
     }
 
+    /// Returns the `segment` associated to the `SegmentEntry`.
+    pub fn segment(&self) -> &Segment {
+        &self.segment
+    }
     /// Accessor to the `SegmentMeta`
     pub fn meta(&self) -> &SegmentMeta {
-        &self.meta
+        self.segment.meta()
     }
 }
 
 impl fmt::Debug for SegmentEntry {
     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(formatter, "SegmentEntry({:?})", self.meta)
+        write!(formatter, "SegmentEntry({:?})", self.meta())
     }
 }

src/indexer/segment_manager.rs

@@ -2,15 +2,15 @@ use super::segment_register::SegmentRegister;
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::error::TantivyError;
-use crate::indexer::delete_queue::DeleteCursor;
+use crate::indexer::{SegmentEntry, MergeOperationInventory, MergeCandidate, MergeOperation};
-use crate::indexer::SegmentEntry;
+use crate::{Segment, Opstamp};
 use std::collections::hash_set::HashSet;
 use std::fmt::{self, Debug, Formatter};
-use std::sync::RwLock;
+use std::sync::{Arc, RwLock};
 use std::sync::{RwLockReadGuard, RwLockWriteGuard};
 
 #[derive(Default)]
-struct SegmentRegisters {
+pub(crate) struct SegmentRegisters {
     uncommitted: SegmentRegister,
     committed: SegmentRegister,
 }
@@ -22,6 +22,17 @@ pub(crate) enum SegmentsStatus {
 }
 
 impl SegmentRegisters {
+    pub fn new(committed: SegmentRegister) -> SegmentRegisters {
+        SegmentRegisters {
+            uncommitted: Default::default(),
+            committed,
+        }
+    }
+
+    pub fn committed_segment(&self) -> Vec<Segment> {
+        self.committed.segments()
+    }
+
     /// Check if all the segments are committed or uncommited.
     ///
     /// If some segment is missing or segments are in a different state (this should not happen
@@ -44,7 +55,8 @@ impl SegmentRegisters {
 /// changes (merges especially)
 #[derive(Default)]
 pub struct SegmentManager {
-    registers: RwLock<SegmentRegisters>,
+    registers: Arc<RwLock<SegmentRegisters>>,
+    merge_operations: MergeOperationInventory,
 }
 
 impl Debug for SegmentManager {
@@ -58,34 +70,28 @@ impl Debug for SegmentManager {
     }
 }
 
-pub fn get_mergeable_segments(
-    in_merge_segment_ids: &HashSet<SegmentId>,
-    segment_manager: &SegmentManager,
-) -> (Vec<SegmentMeta>, Vec<SegmentMeta>) {
-    let registers_lock = segment_manager.read();
-    (
-        registers_lock
-            .committed
-            .get_mergeable_segments(in_merge_segment_ids),
-        registers_lock
-            .uncommitted
-            .get_mergeable_segments(in_merge_segment_ids),
-    )
-}
 
 impl SegmentManager {
-    pub fn from_segments(
+    pub(crate) fn new(registers: Arc<RwLock<SegmentRegisters>>) -> SegmentManager {
-        segment_metas: Vec<SegmentMeta>,
-        delete_cursor: &DeleteCursor,
-    ) -> SegmentManager {
         SegmentManager {
-            registers: RwLock::new(SegmentRegisters {
+            registers,
-                uncommitted: SegmentRegister::default(),
+            merge_operations: Default::default()
-                committed: SegmentRegister::new(segment_metas, delete_cursor),
-            }),
         }
     }
 
+    pub fn new_merge_operation(&self, opstamp: Opstamp, merge_candidate: MergeCandidate) -> MergeOperation {
+        MergeOperation::new(
+            &self.merge_operations,
+            opstamp,
+            merge_candidate.0
+
+        )
+    }
+
+    pub fn wait_merging_thread(&self) {
+        self.merge_operations.wait_until_empty()
+    }
+
     /// Returns all of the segment entries (committed or uncommitted)
     pub fn segment_entries(&self) -> Vec<SegmentEntry> {
         let registers_lock = self.read();
@@ -94,6 +100,34 @@ impl SegmentManager {
         segment_entries
     }
 
+    /// Returns the segments that are currently not in merge.
+    ///
+    /// They are split over two `Vec`. The committed segments on one hand
+    /// and the uncommitted ones on the other hand.
+    ///
+    /// This method is useful when searching for merge candidate or segments
+    /// to persists.
+    pub fn segments_not_in_merge(&self) -> (Vec<SegmentMeta>, Vec<SegmentMeta>) {
+        let in_merge_segment_ids: HashSet<SegmentId> = self.merge_operations.segment_in_merge();
+        let registers_lock = self.read();
+        (
+            registers_lock
+                .committed
+                .get_mergeable_segments(&in_merge_segment_ids),
+            registers_lock
+                .uncommitted
+                .get_mergeable_segments(&in_merge_segment_ids),
+        )
+    }
+
+    pub fn largest_segment_not_in_merge(&self) -> Option<SegmentMeta> {
+        let (committed, uncommitted) = self.segments_not_in_merge();
+        let mut segments = vec![];
+        segments.extend(committed);
+        segments.extend(uncommitted);
+        None
+    }
+
     // Lock poisoning should never happen :
     // The lock is acquired and released within this class,
     // and the operations cannot panic.

src/indexer/segment_register.rs

@@ -1,7 +1,10 @@
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
+use crate::directory::ManagedDirectory;
 use crate::indexer::delete_queue::DeleteCursor;
 use crate::indexer::segment_entry::SegmentEntry;
+use crate::schema::Schema;
+use crate::Segment;
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::fmt::{self, Debug, Formatter};
@@ -46,6 +49,13 @@ impl SegmentRegister {
             .collect()
     }
 
+    pub fn segments(&self) -> Vec<Segment> {
+        self.segment_states
+            .values()
+            .map(|segment_entry| segment_entry.segment().clone())
+            .collect()
+    }
+
     pub fn segment_entries(&self) -> Vec<SegmentEntry> {
         self.segment_states.values().cloned().collect()
     }
@@ -79,11 +89,17 @@ impl SegmentRegister {
         self.segment_states.get(segment_id).cloned()
     }
 
-    pub fn new(segment_metas: Vec<SegmentMeta>, delete_cursor: &DeleteCursor) -> SegmentRegister {
+    pub fn new(
+        directory: &ManagedDirectory,
+        schema: &Schema,
+        segment_metas: Vec<SegmentMeta>,
+        delete_cursor: &DeleteCursor,
+    ) -> SegmentRegister {
         let mut segment_states = HashMap::new();
         for segment_meta in segment_metas {
             let segment_id = segment_meta.id();
-            let segment_entry = SegmentEntry::new(segment_meta, delete_cursor.clone(), None);
+            let segment = Segment::new_persisted(segment_meta, directory.clone(), schema.clone());
+            let segment_entry = SegmentEntry::new(segment, delete_cursor.clone(), None);
             segment_states.insert(segment_id, segment_entry);
         }
         SegmentRegister { segment_states }
@@ -95,6 +111,7 @@ mod tests {
     use super::*;
     use crate::core::{SegmentId, SegmentMetaInventory};
     use crate::indexer::delete_queue::*;
+    use crate::indexer::ResourceManager;
 
     fn segment_ids(segment_register: &SegmentRegister) -> Vec<SegmentId> {
         segment_register
@@ -108,28 +125,34 @@ mod tests {
     fn test_segment_register() {
         let inventory = SegmentMetaInventory::default();
         let delete_queue = DeleteQueue::new();
+        let schema = Schema::builder().build();
 
         let mut segment_register = SegmentRegister::default();
         let segment_id_a = SegmentId::generate_random();
         let segment_id_b = SegmentId::generate_random();
         let segment_id_merged = SegmentId::generate_random();
 
+        let memory_manager = ResourceManager::default();
+
         {
-            let segment_meta = inventory.new_segment_meta(segment_id_a, 0u32);
+            let meta = inventory.new_segment_meta(segment_id_a, 0u32);
-            let segment_entry = SegmentEntry::new(segment_meta, delete_queue.cursor(), None);
+            let segment = Segment::new_volatile(meta, schema.clone(), memory_manager.clone());
+            let segment_entry = SegmentEntry::new(segment, delete_queue.cursor(), None);
             segment_register.add_segment_entry(segment_entry);
         }
         assert_eq!(segment_ids(&segment_register), vec![segment_id_a]);
         {
-            let segment_meta = inventory.new_segment_meta(segment_id_b, 0u32);
+            let meta = inventory.new_segment_meta(segment_id_b, 0u32);
-            let segment_entry = SegmentEntry::new(segment_meta, delete_queue.cursor(), None);
+            let segment = Segment::new_volatile(meta, schema.clone(), memory_manager.clone());
+            let segment_entry = SegmentEntry::new(segment, delete_queue.cursor(), None);
             segment_register.add_segment_entry(segment_entry);
         }
         segment_register.remove_segment(&segment_id_a);
         segment_register.remove_segment(&segment_id_b);
         {
             let segment_meta_merged = inventory.new_segment_meta(segment_id_merged, 0u32);
-            let segment_entry = SegmentEntry::new(segment_meta_merged, delete_queue.cursor(), None);
+            let segment_merged = Segment::new_volatile(segment_meta_merged, schema.clone(), memory_manager.clone());
+            let segment_entry = SegmentEntry::new(segment_merged, delete_queue.cursor(), None);
             segment_register.add_segment_entry(segment_entry);
         }
         assert_eq!(segment_ids(&segment_register), vec![segment_id_merged]);

src/indexer/segment_serializer.rs

@@ -3,43 +3,32 @@ use crate::core::SegmentComponent;
 use crate::fastfield::FastFieldSerializer;
 use crate::fieldnorm::FieldNormsSerializer;
 use crate::postings::InvertedIndexSerializer;
-use crate::store::StoreWriter;
 
 /// Segment serializer is in charge of laying out on disk
 /// the data accumulated and sorted by the `SegmentWriter`.
 pub struct SegmentSerializer {
-    segment: Segment,
-    store_writer: StoreWriter,
     fast_field_serializer: FastFieldSerializer,
-    fieldnorms_serializer: Option<FieldNormsSerializer>,
+    fieldnorms_serializer: FieldNormsSerializer,
     postings_serializer: InvertedIndexSerializer,
 }
 
 impl SegmentSerializer {
     /// Creates a new `SegmentSerializer`.
-    pub fn for_segment(mut segment: Segment) -> crate::Result<SegmentSerializer> {
+    pub fn for_segment(segment: &mut Segment) -> crate::Result<SegmentSerializer> {
-        let store_write = segment.open_write(SegmentComponent::STORE)?;
-
         let fast_field_write = segment.open_write(SegmentComponent::FASTFIELDS)?;
         let fast_field_serializer = FastFieldSerializer::from_write(fast_field_write)?;
 
         let fieldnorms_write = segment.open_write(SegmentComponent::FIELDNORMS)?;
         let fieldnorms_serializer = FieldNormsSerializer::from_write(fieldnorms_write)?;
 
-        let postings_serializer = InvertedIndexSerializer::open(&mut segment)?;
+        let postings_serializer = InvertedIndexSerializer::open(segment)?;
         Ok(SegmentSerializer {
-            segment,
-            store_writer: StoreWriter::new(store_write),
             fast_field_serializer,
-            fieldnorms_serializer: Some(fieldnorms_serializer),
+            fieldnorms_serializer,
             postings_serializer,
         })
     }
 
-    pub fn segment(&self) -> &Segment {
-        &self.segment
-    }
-
     /// Accessor to the `PostingsSerializer`.
     pub fn get_postings_serializer(&mut self) -> &mut InvertedIndexSerializer {
         &mut self.postings_serializer
@@ -50,26 +39,16 @@ impl SegmentSerializer {
         &mut self.fast_field_serializer
     }
 
-    /// Extract the field norm serializer.
+    /// Accessor to the field norm serializer.
-    ///
+    pub fn get_fieldnorms_serializer(&mut self) -> &mut FieldNormsSerializer {
-    /// Note the fieldnorms serializer can only be extracted once.
+        &mut self.fieldnorms_serializer
-    pub fn extract_fieldnorms_serializer(&mut self) -> Option<FieldNormsSerializer> {
-        self.fieldnorms_serializer.take()
-    }
-
-    /// Accessor to the `StoreWriter`.
-    pub fn get_store_writer(&mut self) -> &mut StoreWriter {
-        &mut self.store_writer
     }
 
     /// Finalize the segment serialization.
-    pub fn close(mut self) -> crate::Result<()> {
+    pub fn close(self) -> crate::Result<()> {
-        if let Some(fieldnorms_serializer) = self.extract_fieldnorms_serializer() {
-            fieldnorms_serializer.close()?;
-        }
         self.fast_field_serializer.close()?;
         self.postings_serializer.close()?;
-        self.store_writer.close()?;
+        self.fieldnorms_serializer.close()?;
         Ok(())
     }
 }

src/indexer/segment_updater.rs

@@ -1,4 +1,4 @@
-use super::segment_manager::{get_mergeable_segments, SegmentManager};
+use super::segment_manager::SegmentManager;
 use crate::core::Index;
 use crate::core::IndexMeta;
 use crate::core::Segment;
@@ -7,22 +7,21 @@ use crate::core::SegmentMeta;
 use crate::core::SerializableSegment;
 use crate::core::META_FILEPATH;
 use crate::directory::{Directory, DirectoryClone, GarbageCollectionResult};
-use crate::indexer::delete_queue::DeleteCursor;
 use crate::indexer::index_writer::advance_deletes;
-use crate::indexer::merge_operation::MergeOperationInventory;
 use crate::indexer::merger::IndexMerger;
-use crate::indexer::segment_manager::SegmentsStatus;
+use crate::indexer::segment_manager::{SegmentRegisters, SegmentsStatus};
 use crate::indexer::stamper::Stamper;
 use crate::indexer::SegmentEntry;
 use crate::indexer::SegmentSerializer;
 use crate::indexer::{DefaultMergePolicy, MergePolicy};
 use crate::indexer::{MergeCandidate, MergeOperation};
 use crate::schema::Schema;
-use crate::Opstamp;
+use crate::{Opstamp, SegmentComponent};
 use futures::channel::oneshot;
 use futures::executor::{ThreadPool, ThreadPoolBuilder};
 use futures::future::Future;
 use futures::future::TryFutureExt;
+use serde_json;
 use std::borrow::BorrowMut;
 use std::collections::HashSet;
 use std::io::Write;
@@ -43,7 +42,7 @@ const NUM_MERGE_THREADS: usize = 4;
 /// and flushed.
 ///
 /// This method is not part of tantivy's public API
-pub fn save_new_metas(schema: Schema, directory: &dyn Directory) -> crate::Result<()> {
+pub fn save_new_metas(schema: Schema, directory: &mut dyn Directory) -> crate::Result<()> {
     save_metas(
         &IndexMeta {
             segments: Vec::new(),
@@ -64,7 +63,7 @@ pub fn save_new_metas(schema: Schema, directory: &dyn Directory) -> crate::Resul
 /// and flushed.
 ///
 /// This method is not part of tantivy's public API
-fn save_metas(metas: &IndexMeta, directory: &dyn Directory) -> crate::Result<()> {
+fn save_metas(metas: &IndexMeta, directory: &mut dyn Directory) -> crate::Result<()> {
     info!("save metas");
     let mut buffer = serde_json::to_vec_pretty(metas)?;
     // Just adding a new line at the end of the buffer.
@@ -112,33 +111,36 @@ fn merge(
     target_opstamp: Opstamp,
 ) -> crate::Result<SegmentEntry> {
     // first we need to apply deletes to our segment.
-    let merged_segment = index.new_segment();
+    let mut merged_segment = index.new_segment();
 
     // First we apply all of the delet to the merged segment, up to the target opstamp.
     for segment_entry in &mut segment_entries {
-        let segment = index.segment(segment_entry.meta().clone());
+        advance_deletes(segment_entry, target_opstamp)?;
-        advance_deletes(segment, segment_entry, target_opstamp)?;
     }
 
-    let delete_cursor = segment_entries[0].delete_cursor().clone();
+    let delete_cursor = segment_entries[0].delete_cursor();
 
     let segments: Vec<Segment> = segment_entries
         .iter()
-        .map(|segment_entry| index.segment(segment_entry.meta().clone()))
+        .map(|segment_entry| segment_entry.segment().clone())
         .collect();
 
     // An IndexMerger is like a "view" of our merged segments.
     let merger: IndexMerger = IndexMerger::open(index.schema(), &segments[..])?;
 
     // ... we just serialize this index merger in our new segment to merge the two segments.
-    let segment_serializer = SegmentSerializer::for_segment(merged_segment.clone())?;
+    let segment_serializer = SegmentSerializer::for_segment(&mut merged_segment)?;
 
-    let num_docs = merger.write(segment_serializer)?;
+    let store_wrt = merged_segment.open_write(SegmentComponent::STORE)?;
+    merger.write_storable_fields(store_wrt)?;
 
-    let merged_segment_id = merged_segment.id();
+    let max_doc = merger.write(segment_serializer)?;
 
-    let segment_meta = index.new_segment_meta(merged_segment_id, num_docs);
+    Ok(SegmentEntry::new(
-    Ok(SegmentEntry::new(segment_meta, delete_cursor, None))
+        merged_segment.with_max_doc(max_doc),
+        delete_cursor,
+        None,
+    ))
 }
 
 pub(crate) struct InnerSegmentUpdater {
@@ -154,20 +156,18 @@ pub(crate) struct InnerSegmentUpdater {
 
     index: Index,
     segment_manager: SegmentManager,
-    merge_policy: RwLock<Arc<dyn MergePolicy>>,
+    merge_policy: RwLock<Arc<Box<dyn MergePolicy>>>,
     killed: AtomicBool,
     stamper: Stamper,
-    merge_operations: MergeOperationInventory,
 }
 
 impl SegmentUpdater {
     pub fn create(
+        segment_registers: Arc<RwLock<SegmentRegisters>>,
         index: Index,
         stamper: Stamper,
-        delete_cursor: &DeleteCursor,
     ) -> crate::Result<SegmentUpdater> {
-        let segments = index.searchable_segment_metas()?;
+        let segment_manager = SegmentManager::new(segment_registers);
-        let segment_manager = SegmentManager::from_segments(segments, delete_cursor);
         let pool = ThreadPoolBuilder::new()
             .name_prefix("segment_updater")
             .pool_size(1)
@@ -193,19 +193,18 @@ impl SegmentUpdater {
             merge_thread_pool,
             index,
             segment_manager,
-            merge_policy: RwLock::new(Arc::new(DefaultMergePolicy::default())),
+            merge_policy: RwLock::new(Arc::new(Box::new(DefaultMergePolicy::default()))),
             killed: AtomicBool::new(false),
             stamper,
-            merge_operations: Default::default(),
         })))
     }
 
-    pub fn get_merge_policy(&self) -> Arc<dyn MergePolicy> {
+    pub fn get_merge_policy(&self) -> Arc<Box<dyn MergePolicy>> {
         self.merge_policy.read().unwrap().clone()
     }
 
     pub fn set_merge_policy(&self, merge_policy: Box<dyn MergePolicy>) {
-        let arc_merge_policy = Arc::from(merge_policy);
+        let arc_merge_policy = Arc::new(merge_policy);
         *self.merge_policy.write().unwrap() = arc_merge_policy;
     }
 
@@ -262,8 +261,7 @@ impl SegmentUpdater {
     fn purge_deletes(&self, target_opstamp: Opstamp) -> crate::Result<Vec<SegmentEntry>> {
         let mut segment_entries = self.segment_manager.segment_entries();
         for segment_entry in &mut segment_entries {
-            let segment = self.index.segment(segment_entry.meta().clone());
+            advance_deletes(segment_entry, target_opstamp)?;
-            advance_deletes(segment, segment_entry, target_opstamp)?;
         }
         Ok(segment_entries)
     }
@@ -331,12 +329,21 @@ impl SegmentUpdater {
         &self,
         opstamp: Opstamp,
         payload: Option<String>,
+        soft_commit: bool,
     ) -> impl Future<Output = crate::Result<()>> {
         let segment_updater: SegmentUpdater = self.clone();
+        let directory = self.index.directory().clone();
         self.schedule_future(async move {
-            let segment_entries = segment_updater.purge_deletes(opstamp)?;
+            let mut segment_entries = segment_updater.purge_deletes(opstamp)?;
+            if !soft_commit {
+                for segment_entry in &mut segment_entries {
+                    segment_entry.persist(directory.clone())?;
+                }
+            }
             segment_updater.segment_manager.commit(segment_entries);
-            segment_updater.save_metas(opstamp, payload)?;
+            if !soft_commit {
+                segment_updater.save_metas(opstamp, payload)?;
+            }
             let _ = garbage_collect_files(segment_updater.clone()).await;
             segment_updater.consider_merge_options().await;
             Ok(())
@@ -353,7 +360,7 @@ impl SegmentUpdater {
 
     pub(crate) fn make_merge_operation(&self, segment_ids: &[SegmentId]) -> MergeOperation {
         let commit_opstamp = self.load_metas().opstamp;
-        MergeOperation::new(&self.merge_operations, commit_opstamp, segment_ids.to_vec())
+        self.segment_manager.new_merge_operation(commit_opstamp, MergeCandidate(segment_ids.to_vec()))
     }
 
     // Starts a merge operation. This function will block until the merge operation is effectively
@@ -427,9 +434,8 @@ impl SegmentUpdater {
     }
 
     async fn consider_merge_options(&self) {
-        let merge_segment_ids: HashSet<SegmentId> = self.merge_operations.segment_in_merge();
         let (committed_segments, uncommitted_segments) =
-            get_mergeable_segments(&merge_segment_ids, &self.segment_manager);
+            self.segment_manager.segments_not_in_merge();
 
         // Committed segments cannot be merged with uncommitted_segments.
         // We therefore consider merges using these two sets of segments independently.
@@ -440,7 +446,7 @@ impl SegmentUpdater {
             .compute_merge_candidates(&uncommitted_segments)
             .into_iter()
             .map(|merge_candidate| {
-                MergeOperation::new(&self.merge_operations, current_opstamp, merge_candidate.0)
+                self.segment_manager.new_merge_operation(current_opstamp, merge_candidate)
             })
             .collect();
 
@@ -449,9 +455,10 @@ impl SegmentUpdater {
             .compute_merge_candidates(&committed_segments)
             .into_iter()
             .map(|merge_candidate: MergeCandidate| {
-                MergeOperation::new(&self.merge_operations, commit_opstamp, merge_candidate.0)
+                self.segment_manager.new_merge_operation(commit_opstamp, merge_candidate)
-            });
+            })
-        merge_candidates.extend(committed_merge_candidates);
+            .collect::<Vec<_>>();
+        merge_candidates.extend(committed_merge_candidates.into_iter());
 
         for merge_operation in merge_candidates {
             if let Err(err) = self.start_merge(merge_operation) {
@@ -473,17 +480,13 @@ impl SegmentUpdater {
         let end_merge_future = self.schedule_future(async move {
             info!("End merge {:?}", after_merge_segment_entry.meta());
             {
-                let mut delete_cursor = after_merge_segment_entry.delete_cursor().clone();
+                let mut delete_cursor = after_merge_segment_entry.delete_cursor();
                 if let Some(delete_operation) = delete_cursor.get() {
                     let committed_opstamp = segment_updater.load_metas().opstamp;
                     if delete_operation.opstamp < committed_opstamp {
-                        let index = &segment_updater.index;
+                        if let Err(e) =
-                        let segment = index.segment(after_merge_segment_entry.meta().clone());
+                            advance_deletes(&mut after_merge_segment_entry, committed_opstamp)
-                        if let Err(e) = advance_deletes(
+                        {
-                            segment,
-                            &mut after_merge_segment_entry,
-                            committed_opstamp,
-                        ) {
                             error!(
                                 "Merge of {:?} was cancelled (advancing deletes failed): {:?}",
                                 merge_operation.segment_ids(),
@@ -521,7 +524,7 @@ impl SegmentUpdater {
     ///
     /// Upon termination of the current merging threads,
     /// merge opportunity may appear.
-    ///
+    //
     /// We keep waiting until the merge policy judges that
     /// no opportunity is available.
     ///
@@ -532,9 +535,8 @@ impl SegmentUpdater {
     ///
     /// Obsolete files will eventually be cleaned up
     /// by the directory garbage collector.
-    pub fn wait_merging_thread(&self) -> crate::Result<()> {
+    pub fn wait_merging_thread(&self) {
-        self.merge_operations.wait_until_empty();
+        self.segment_manager.wait_merging_thread()
-        Ok(())
     }
 }
 
@@ -543,7 +545,8 @@ mod tests {
 
     use crate::indexer::merge_policy::tests::MergeWheneverPossible;
     use crate::schema::*;
-    use crate::Index;
+    use crate::{Index, SegmentId};
+    use futures::executor::block_on;
 
     #[test]
     fn test_delete_during_merge() {
@@ -554,7 +557,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
 
         // writing the segment
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.set_merge_policy(Box::new(MergeWheneverPossible));
 
         {
@@ -607,7 +610,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
 
         // writing the segment
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
 
         {
             for _ in 0..100 {
@@ -678,7 +681,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
 
         // writing the segment
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
 
         {
             for _ in 0..100 {
@@ -694,4 +697,27 @@ mod tests {
             .segment_entries();
         assert!(seg_vec.is_empty());
     }
+
+    #[test]
+    fn test_merge_over_soft_commit() {
+        let mut schema_builder = Schema::builder();
+        let text_field = schema_builder.add_text_field("text", TEXT);
+        let schema = schema_builder.build();
+        let index = Index::create_in_ram(schema);
+        // writing the segment
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(text_field=>"a"));
+        assert!(index_writer.soft_commit().is_ok());
+        index_writer.add_document(doc!(text_field=>"a"));
+        assert!(index_writer.soft_commit().is_ok());
+
+        let reader = index_writer.reader(1).unwrap();
+        let segment_ids: Vec<SegmentId> = reader
+            .searcher()
+            .segment_readers()
+            .iter()
+            .map(|reader| reader.segment_id())
+            .collect();
+        assert!(block_on(index_writer.merge(&segment_ids)).is_ok());
+    }
 }

src/indexer/segment_writer.rs

@@ -1,9 +1,11 @@
 use super::operation::AddOperation;
 use crate::core::Segment;
 use crate::core::SerializableSegment;
+use crate::directory::{SpillingResult, SpillingWriter, TerminatingWrite};
 use crate::fastfield::FastFieldsWriter;
-use crate::fieldnorm::{FieldNormReaders, FieldNormsWriter};
+use crate::fieldnorm::FieldNormsWriter;
 use crate::indexer::segment_serializer::SegmentSerializer;
+use crate::indexer::IndexWriterConfig;
 use crate::postings::compute_table_size;
 use crate::postings::MultiFieldPostingsWriter;
 use crate::schema::FieldType;
@@ -11,19 +13,24 @@ use crate::schema::Schema;
 use crate::schema::Term;
 use crate::schema::Value;
 use crate::schema::{Field, FieldEntry};
+use crate::store::StoreWriter;
 use crate::tokenizer::{BoxTokenStream, PreTokenizedStream};
-use crate::tokenizer::{FacetTokenizer, TextAnalyzer};
+use crate::tokenizer::{FacetTokenizer, TextAnalyzer, TokenizerManager};
 use crate::tokenizer::{TokenStreamChain, Tokenizer};
 use crate::Opstamp;
 use crate::{DocId, SegmentComponent};
+use std::io;
+use std::io::Write;
+use std::str;
+use crate::indexer::resource_manager::ResourceManager;
 
 /// Computes the initial size of the hash table.
 ///
 /// Returns a number of bit `b`, such that the recommended initial table size is 2^b.
-fn initial_table_size(per_thread_memory_budget: usize) -> crate::Result<usize> {
+fn initial_table_size(per_thread_memory_budget: u64) -> crate::Result<usize> {
-    let table_memory_upper_bound = per_thread_memory_budget / 3;
+    let table_memory_upper_bound = per_thread_memory_budget / 3u64;
     if let Some(limit) = (10..)
-        .take_while(|num_bits: &usize| compute_table_size(*num_bits) < table_memory_upper_bound)
+        .take_while(|num_bits| compute_table_size(*num_bits) < table_memory_upper_bound)
         .last()
     {
         Ok(limit.min(19)) // we cap it at 2^19 = 512K.
@@ -41,12 +48,13 @@ fn initial_table_size(per_thread_memory_budget: usize) -> crate::Result<usize> {
 pub struct SegmentWriter {
     max_doc: DocId,
     multifield_postings: MultiFieldPostingsWriter,
-    segment_serializer: SegmentSerializer,
+    segment: Segment,
     fast_field_writers: FastFieldsWriter,
     fieldnorms_writer: FieldNormsWriter,
     doc_opstamps: Vec<Opstamp>,
     tokenizers: Vec<Option<TextAnalyzer>>,
-    term_buffer: Term,
+    store_writer: StoreWriter<SpillingWriter>,
+    memory_manager: ResourceManager,
 }
 
 impl SegmentWriter {
@@ -60,13 +68,13 @@ impl SegmentWriter {
     /// - segment: The segment being written
     /// - schema
     pub fn for_segment(
-        memory_budget: usize,
+        config: &IndexWriterConfig,
         segment: Segment,
         schema: &Schema,
+        tokenizer_manager: &TokenizerManager,
+        memory_manager: ResourceManager
     ) -> crate::Result<SegmentWriter> {
-        let tokenizer_manager = segment.index().tokenizers().clone();
+        let table_num_bits = initial_table_size(config.heap_size_in_byte_per_thread())?;
-        let table_num_bits = initial_table_size(memory_budget)?;
-        let segment_serializer = SegmentSerializer::for_segment(segment)?;
         let multifield_postings = MultiFieldPostingsWriter::new(schema, table_num_bits);
         let tokenizers = schema
             .fields()
@@ -82,15 +90,26 @@ impl SegmentWriter {
                 },
             )
             .collect();
+        let mut segment_clone = segment.clone();
+        let spilling_wrt = SpillingWriter::new(
+            50_000_000,
+            Box::new(move || {
+                segment_clone
+                    .open_write(SegmentComponent::STORE)
+                    .map_err(|err| io::Error::new(io::ErrorKind::Other, err))
+            }),
+        );
+        let store_writer = StoreWriter::new(spilling_wrt);
         Ok(SegmentWriter {
             max_doc: 0,
             multifield_postings,
             fieldnorms_writer: FieldNormsWriter::for_schema(schema),
-            segment_serializer,
+            segment,
             fast_field_writers: FastFieldsWriter::from_schema(schema),
             doc_opstamps: Vec::with_capacity(1_000),
             tokenizers,
-            term_buffer: Term::new(),
+            store_writer,
+            memory_manager
         })
     }
 
@@ -98,29 +117,40 @@ impl SegmentWriter {
     ///
     /// Finalize consumes the `SegmentWriter`, so that it cannot
     /// be used afterwards.
-    pub fn finalize(mut self) -> crate::Result<Vec<u64>> {
+    pub fn finalize(mut self) -> crate::Result<(Segment, Vec<u64>)> {
         self.fieldnorms_writer.fill_up_to_max_doc(self.max_doc);
+        let spilling_wrt = self.store_writer.close()?;
+        let mut segment: Segment;
+        match spilling_wrt.finalize()? {
+            SpillingResult::Spilled => {
+                segment = self.segment.clone();
+            }
+            SpillingResult::Buffer(buf) => {
+                segment = self.segment.into_volatile(self.memory_manager.clone());
+                let mut store_wrt = segment.open_write(SegmentComponent::STORE)?;
+                store_wrt.write_all(&buf[..])?;
+                store_wrt.terminate()?;
+            }
+        }
+        let segment_serializer = SegmentSerializer::for_segment(&mut segment)?;
+        segment = segment.with_max_doc(self.max_doc);
         write(
             &self.multifield_postings,
             &self.fast_field_writers,
             &self.fieldnorms_writer,
-            self.segment_serializer,
+            segment_serializer,
         )?;
-        Ok(self.doc_opstamps)
+        Ok((segment, self.doc_opstamps))
     }
 
-    pub fn mem_usage(&self) -> usize {
+    pub fn mem_usage(&self) -> u64 {
         self.multifield_postings.mem_usage()
     }
 
     /// Indexes a new document
     ///
     /// As a user, you should rather use `IndexWriter`'s add_document.
-    pub fn add_document(
+    pub fn add_document(&mut self, add_operation: AddOperation, schema: &Schema) -> io::Result<()> {
-        &mut self,
-        add_operation: AddOperation,
-        schema: &Schema,
-    ) -> crate::Result<()> {
         let doc_id = self.max_doc;
         let mut doc = add_operation.document;
         self.doc_opstamps.push(add_operation.opstamp);
@@ -128,45 +158,34 @@ impl SegmentWriter {
         self.fast_field_writers.add_document(&doc);
 
         for (field, field_values) in doc.get_sorted_field_values() {
-            let field_entry = schema.get_field_entry(field);
+            let field_options = schema.get_field_entry(field);
-            let make_schema_error = || {
+            if !field_options.is_indexed() {
-                crate::TantivyError::SchemaError(format!(
-                    "Expected a {:?} for field {:?}",
-                    field_entry.field_type().value_type(),
-                    field_entry.name()
-                ))
-            };
-            if !field_entry.is_indexed() {
                 continue;
             }
-            let (term_buffer, multifield_postings) =
+            match *field_options.field_type() {
-                (&mut self.term_buffer, &mut self.multifield_postings);
-            match *field_entry.field_type() {
                 FieldType::HierarchicalFacet => {
-                    term_buffer.set_field(field);
+                    let facets: Vec<&str> = field_values
-                    let facets =
+                        .iter()
-                        field_values
+                        .flat_map(|field_value| match *field_value.value() {
-                            .iter()
+                            Value::Facet(ref facet) => Some(facet.encoded_str()),
-                            .flat_map(|field_value| match *field_value.value() {
+                            _ => {
-                                Value::Facet(ref facet) => Some(facet.encoded_str()),
+                                panic!("Expected hierarchical facet");
-                                _ => {
+                            }
-                                    panic!("Expected hierarchical facet");
+                        })
-                                }
+                        .collect();
-                            });
+                    let mut term = Term::for_field(field); // we set the Term
-                    for facet_str in facets {
+                    for fake_str in facets {
                         let mut unordered_term_id_opt = None;
-                        FacetTokenizer
+                        FacetTokenizer.token_stream(fake_str).process(&mut |token| {
-                            .token_stream(facet_str)
+                            term.set_text(&token.text);
-                            .process(&mut |token| {
+                            let unordered_term_id =
-                                term_buffer.set_text(&token.text);
+                                self.multifield_postings.subscribe(doc_id, &term);
-                                let unordered_term_id =
+                            unordered_term_id_opt = Some(unordered_term_id);
-                                    multifield_postings.subscribe(doc_id, &term_buffer);
+                        });
-                                unordered_term_id_opt = Some(unordered_term_id);
-                            });
                         if let Some(unordered_term_id) = unordered_term_id_opt {
                             self.fast_field_writers
                                 .get_multivalue_writer(field)
-                                .expect("writer for facet missing")
+                                .expect("multified writer for facet missing")
                                 .add_val(unordered_term_id);
                         }
                     }
@@ -183,6 +202,7 @@ impl SegmentWriter {
                                 if let Some(last_token) = tok_str.tokens.last() {
                                     total_offset += last_token.offset_to;
                                 }
+
                                 token_streams
                                     .push(PreTokenizedStream::from(tok_str.clone()).into());
                             }
@@ -192,6 +212,7 @@ impl SegmentWriter {
                                 {
                                     offsets.push(total_offset);
                                     total_offset += text.len();
+
                                     token_streams.push(tokenizer.token_stream(text));
                                 }
                             }
@@ -203,12 +224,8 @@ impl SegmentWriter {
                         0
                     } else {
                         let mut token_stream = TokenStreamChain::new(offsets, token_streams);
-                        multifield_postings.index_text(
+                        self.multifield_postings
-                            doc_id,
+                            .index_text(doc_id, field, &mut token_stream)
-                            field,
-                            &mut token_stream,
-                            term_buffer,
-                        )
                     };
 
                     self.fieldnorms_writer.record(doc_id, field, num_tokens);
@@ -216,74 +233,55 @@ impl SegmentWriter {
                 FieldType::U64(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
+                            let term = Term::from_field_u64(
-                            let u64_val = field_value
+                                field_value.field(),
-                                .value()
+                                field_value.value().u64_value(),
-                                .u64_value()
+                            );
-                                .ok_or_else(make_schema_error)?;
+                            self.multifield_postings.subscribe(doc_id, &term);
-                            term_buffer.set_u64(u64_val);
-                            multifield_postings.subscribe(doc_id, &term_buffer);
                         }
                     }
                 }
                 FieldType::Date(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
+                            let term = Term::from_field_i64(
-                            let date_val = field_value
+                                field_value.field(),
-                                .value()
+                                field_value.value().date_value().timestamp(),
-                                .date_value()
+                            );
-                                .ok_or_else(make_schema_error)?;
+                            self.multifield_postings.subscribe(doc_id, &term);
-                            term_buffer.set_i64(date_val.timestamp());
-                            multifield_postings.subscribe(doc_id, &term_buffer);
                         }
                     }
                 }
                 FieldType::I64(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
+                            let term = Term::from_field_i64(
-                            let i64_val = field_value
+                                field_value.field(),
-                                .value()
+                                field_value.value().i64_value(),
-                                .i64_value()
+                            );
-                                .ok_or_else(make_schema_error)?;
+                            self.multifield_postings.subscribe(doc_id, &term);
-                            term_buffer.set_i64(i64_val);
-                            multifield_postings.subscribe(doc_id, &term_buffer);
                         }
                     }
                 }
                 FieldType::F64(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
+                            let term = Term::from_field_f64(
-                            let f64_val = field_value
+                                field_value.field(),
-                                .value()
+                                field_value.value().f64_value(),
-                                .f64_value()
+                            );
-                                .ok_or_else(make_schema_error)?;
+                            self.multifield_postings.subscribe(doc_id, &term);
-                            term_buffer.set_f64(f64_val);
-                            multifield_postings.subscribe(doc_id, &term_buffer);
                         }
                     }
                 }
-                FieldType::Bytes(ref option) => {
+                FieldType::Bytes => {
-                    if option.is_indexed() {
+                    // Do nothing. Bytes only supports fast fields.
-                        for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
-                            let bytes = field_value
-                                .value()
-                                .bytes_value()
-                                .ok_or_else(make_schema_error)?;
-                            term_buffer.set_bytes(bytes);
-                            self.multifield_postings.subscribe(doc_id, &term_buffer);
-                        }
-                    }
                 }
             }
         }
         doc.filter_fields(|field| schema.get_field_entry(field).is_stored());
         doc.prepare_for_store();
-        let doc_writer = self.segment_serializer.get_store_writer();
+        self.store_writer.store(&doc)?;
-        doc_writer.store(&doc)?;
         self.max_doc += 1;
         Ok(())
     }
@@ -316,16 +314,9 @@ fn write(
     fieldnorms_writer: &FieldNormsWriter,
     mut serializer: SegmentSerializer,
 ) -> crate::Result<()> {
-    if let Some(fieldnorms_serializer) = serializer.extract_fieldnorms_serializer() {
+    let term_ord_map = multifield_postings.serialize(serializer.get_postings_serializer())?;
-        fieldnorms_writer.serialize(fieldnorms_serializer)?;
-    }
-    let fieldnorm_data = serializer
-        .segment()
-        .open_read(SegmentComponent::FIELDNORMS)?;
-    let fieldnorm_readers = FieldNormReaders::open(fieldnorm_data)?;
-    let term_ord_map =
-        multifield_postings.serialize(serializer.get_postings_serializer(), fieldnorm_readers)?;
     fast_field_writers.serialize(serializer.get_fast_field_serializer(), &term_ord_map)?;
+    fieldnorms_writer.serialize(serializer.get_fieldnorms_serializer())?;
     serializer.close()?;
     Ok(())
 }

src/lib.rs

@@ -105,7 +105,7 @@ extern crate serde_json;
 extern crate log;
 
 #[macro_use]
-extern crate thiserror;
+extern crate failure;
 
 #[cfg(all(test, feature = "unstable"))]
 extern crate test;
@@ -134,7 +134,7 @@ mod core;
 mod indexer;
 
 #[allow(unused_doc_comments)]
-pub mod error;
+mod error;
 pub mod tokenizer;
 
 pub mod collector;
@@ -156,15 +156,14 @@ mod snippet;
 pub use self::snippet::{Snippet, SnippetGenerator};
 
 mod docset;
-pub use self::docset::{DocSet, TERMINATED};
+pub use self::docset::{DocSet, SkipResult};
-pub use crate::common::HasLen;
 pub use crate::common::{f64_to_u64, i64_to_u64, u64_to_f64, u64_to_i64};
 pub use crate::core::{Executor, SegmentComponent};
 pub use crate::core::{Index, IndexMeta, Searcher, Segment, SegmentId, SegmentMeta};
 pub use crate::core::{InvertedIndexReader, SegmentReader};
 pub use crate::directory::Directory;
 pub use crate::indexer::operation::UserOperation;
-pub use crate::indexer::IndexWriter;
+pub use crate::indexer::{IndexWriter, IndexWriterConfig};
 pub use crate::postings::Postings;
 pub use crate::reader::LeasedItem;
 pub use crate::schema::{Document, Term};
@@ -174,7 +173,7 @@ use once_cell::sync::Lazy;
 use serde::{Deserialize, Serialize};
 
 /// Index format version.
-const INDEX_FORMAT_VERSION: u32 = 3;
+const INDEX_FORMAT_VERSION: u32 = 1;
 
 /// Structure version for the index.
 #[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -246,10 +245,11 @@ pub type DocId = u32;
 /// with opstamp `n+1`.
 pub type Opstamp = u64;
 
-/// A Score that represents the relevance of the document to the query
+/// A f32 that represents the relevance of the document to the query
 ///
-/// This is modelled internally as a `f32`. The larger the number, the more relevant
+/// This is modelled internally as a `f32`. The
-/// the document to the search query.
+/// larger the number, the more relevant the document
+/// to the search
 pub type Score = f32;
 
 /// A `SegmentLocalId` identifies a segment.
@@ -277,18 +277,20 @@ impl DocAddress {
 ///
 /// The id used for the segment is actually an ordinal
 /// in the list of `Segment`s held by a `Searcher`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub struct DocAddress(pub SegmentLocalId, pub DocId);
 
 #[cfg(test)]
 mod tests {
+
     use crate::collector::tests::TEST_COLLECTOR_WITH_SCORE;
     use crate::core::SegmentReader;
-    use crate::docset::{DocSet, TERMINATED};
+    use crate::docset::DocSet;
     use crate::query::BooleanQuery;
     use crate::schema::*;
     use crate::DocAddress;
     use crate::Index;
+    use crate::IndexWriter;
     use crate::Postings;
     use crate::ReloadPolicy;
     use rand::distributions::Bernoulli;
@@ -296,26 +298,17 @@ mod tests {
     use rand::rngs::StdRng;
     use rand::{Rng, SeedableRng};
 
-    /// Checks if left and right are close one to each other.
+    pub fn assert_nearly_equals(expected: f32, val: f32) {
-    /// Panics if the two values are more than 0.5% apart.
+        assert!(
-    #[macro_export]
+            nearly_equals(val, expected),
-    macro_rules! assert_nearly_equals {
+            "Got {}, expected {}.",
-        ($left:expr, $right:expr) => {{
+            val,
-            match (&$left, &$right) {
+            expected
-                (left_val, right_val) => {
+        );
-                    let diff = (left_val - right_val).abs();
+    }
-                    let add = left_val.abs() + right_val.abs();
+
-                    if diff > 0.0005 * add {
+    pub fn nearly_equals(a: f32, b: f32) -> bool {
-                        panic!(
+        (a - b).abs() < 0.0005 * (a + b).abs()
-                            r#"assertion failed: `(left ~= right)`
-  left: `{:?}`,
- right: `{:?}`"#,
-                            &*left_val, &*right_val
-                        )
-                    }
-                }
-            }
-        }};
     }
 
     pub fn generate_nonunique_unsorted(max_value: u32, n_elems: usize) -> Vec<u32> {
@@ -353,14 +346,14 @@ mod tests {
 
     #[test]
     #[cfg(feature = "mmap")]
-    fn test_indexing() -> crate::Result<()> {
+    fn test_indexing() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
         let index = Index::create_from_tempdir(schema).unwrap();
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             {
                 let doc = doc!(text_field=>"af b");
                 index_writer.add_document(doc);
@@ -375,91 +368,120 @@ mod tests {
             }
             assert!(index_writer.commit().is_ok());
         }
-        Ok(())
     }
 
     #[test]
-    fn test_docfreq1() -> crate::Result<()> {
+    fn test_docfreq1() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let index = Index::create_in_ram(schema_builder.build());
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-        index_writer.add_document(doc!(text_field=>"a b c"));
+        {
-        index_writer.commit()?;
+            index_writer.add_document(doc!(text_field=>"a b c"));
-        index_writer.add_document(doc!(text_field=>"a"));
+            index_writer.commit().unwrap();
-        index_writer.add_document(doc!(text_field=>"a a"));
+        }
-        index_writer.commit()?;
+        {
-        index_writer.add_document(doc!(text_field=>"c"));
+            {
-        index_writer.commit()?;
+                let doc = doc!(text_field=>"a");
-        let reader = index.reader()?;
+                index_writer.add_document(doc);
-        let searcher = reader.searcher();
+            }
-        let term_a = Term::from_field_text(text_field, "a");
+            {
-        assert_eq!(searcher.doc_freq(&term_a)?, 3);
+                let doc = doc!(text_field=>"a a");
-        let term_b = Term::from_field_text(text_field, "b");
+                index_writer.add_document(doc);
-        assert_eq!(searcher.doc_freq(&term_b)?, 1);
+            }
-        let term_c = Term::from_field_text(text_field, "c");
+            index_writer.commit().unwrap();
-        assert_eq!(searcher.doc_freq(&term_c)?, 2);
+        }
-        let term_d = Term::from_field_text(text_field, "d");
+        {
-        assert_eq!(searcher.doc_freq(&term_d)?, 0);
+            let doc = doc!(text_field=>"c");
-        Ok(())
+            index_writer.add_document(doc);
+            index_writer.commit().unwrap();
+        }
+        {
+            let reader = index.reader().unwrap();
+            let searcher = reader.searcher();
+            let term_a = Term::from_field_text(text_field, "a");
+            assert_eq!(searcher.doc_freq(&term_a), 3);
+            let term_b = Term::from_field_text(text_field, "b");
+            assert_eq!(searcher.doc_freq(&term_b), 1);
+            let term_c = Term::from_field_text(text_field, "c");
+            assert_eq!(searcher.doc_freq(&term_c), 2);
+            let term_d = Term::from_field_text(text_field, "d");
+            assert_eq!(searcher.doc_freq(&term_d), 0);
+        }
     }
 
     #[test]
-    fn test_fieldnorm_no_docs_with_field() -> crate::Result<()> {
+    fn test_fieldnorm_no_docs_with_field() {
         let mut schema_builder = Schema::builder();
         let title_field = schema_builder.add_text_field("title", TEXT);
         let text_field = schema_builder.add_text_field("text", TEXT);
         let index = Index::create_in_ram(schema_builder.build());
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(text_field=>"a b c"));
-        index_writer.commit()?;
-        let index_reader = index.reader()?;
-        let searcher = index_reader.searcher();
-        let reader = searcher.segment_reader(0);
         {
-            let fieldnorm_reader = reader.get_fieldnorms_reader(text_field)?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-            assert_eq!(fieldnorm_reader.fieldnorm(0), 3);
+            {
+                let doc = doc!(text_field=>"a b c");
+                index_writer.add_document(doc);
+            }
+            index_writer.commit().unwrap();
         }
         {
-            let fieldnorm_reader = reader.get_fieldnorms_reader(title_field)?;
+            let index_reader = index.reader().unwrap();
-            assert_eq!(fieldnorm_reader.fieldnorm_id(0), 0);
+            let searcher = index_reader.searcher();
+            let reader = searcher.segment_reader(0);
+            {
+                let fieldnorm_reader = reader.get_fieldnorms_reader(text_field);
+                assert_eq!(fieldnorm_reader.fieldnorm(0), 3);
+            }
+            {
+                let fieldnorm_reader = reader.get_fieldnorms_reader(title_field);
+                assert_eq!(fieldnorm_reader.fieldnorm_id(0), 0);
+            }
         }
-        Ok(())
     }
 
     #[test]
-    fn test_fieldnorm() -> crate::Result<()> {
+    fn test_fieldnorm() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let index = Index::create_in_ram(schema_builder.build());
-        let mut index_writer = index.writer_for_tests()?;
+        {
-        index_writer.add_document(doc!(text_field=>"a b c"));
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-        index_writer.add_document(doc!());
+            {
-        index_writer.add_document(doc!(text_field=>"a b"));
+                let doc = doc!(text_field=>"a b c");
-        index_writer.commit()?;
+                index_writer.add_document(doc);
-        let reader = index.reader()?;
+            }
-        let searcher = reader.searcher();
+            {
-        let segment_reader: &SegmentReader = searcher.segment_reader(0);
+                let doc = doc!();
-        let fieldnorms_reader = segment_reader.get_fieldnorms_reader(text_field)?;
+                index_writer.add_document(doc);
-        assert_eq!(fieldnorms_reader.fieldnorm(0), 3);
+            }
-        assert_eq!(fieldnorms_reader.fieldnorm(1), 0);
+            {
-        assert_eq!(fieldnorms_reader.fieldnorm(2), 2);
+                let doc = doc!(text_field=>"a b");
-        Ok(())
+                index_writer.add_document(doc);
+            }
+            index_writer.commit().unwrap();
+        }
+        {
+            let reader = index.reader().unwrap();
+            let searcher = reader.searcher();
+            let segment_reader: &SegmentReader = searcher.segment_reader(0);
+            let fieldnorms_reader = segment_reader.get_fieldnorms_reader(text_field);
+            assert_eq!(fieldnorms_reader.fieldnorm(0), 3);
+            assert_eq!(fieldnorms_reader.fieldnorm(1), 0);
+            assert_eq!(fieldnorms_reader.fieldnorm(2), 2);
+        }
     }
 
     fn advance_undeleted(docset: &mut dyn DocSet, reader: &SegmentReader) -> bool {
-        let mut doc = docset.advance();
+        while docset.advance() {
-        while doc != TERMINATED {
+            if !reader.is_deleted(docset.doc()) {
-            if !reader.is_deleted(doc) {
                 return true;
             }
-            doc = docset.advance();
         }
         false
     }
 
     #[test]
-    fn test_delete_postings1() -> crate::Result<()> {
+    fn test_delete_postings1() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let term_abcd = Term::from_field_text(text_field, "abcd");
@@ -475,7 +497,7 @@ mod tests {
             .unwrap();
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             // 0
             index_writer.add_document(doc!(text_field=>"a b"));
             // 1
@@ -491,19 +513,19 @@ mod tests {
             index_writer.add_document(doc!(text_field=>" b c"));
             // 5
             index_writer.add_document(doc!(text_field=>" a"));
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
         }
         {
-            reader.reload()?;
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             let segment_reader = searcher.segment_reader(0);
-            let inverted_index = segment_reader.inverted_index(text_field)?;
+            let inverted_index = segment_reader.inverted_index(text_field);
             assert!(inverted_index
-                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)
                 .is_none());
             {
                 let mut postings = inverted_index
-                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)?
+                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert!(advance_undeleted(&mut postings, segment_reader));
                 assert_eq!(postings.doc(), 5);
@@ -511,7 +533,7 @@ mod tests {
             }
             {
                 let mut postings = inverted_index
-                    .read_postings(&term_b, IndexRecordOption::WithFreqsAndPositions)?
+                    .read_postings(&term_b, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert!(advance_undeleted(&mut postings, segment_reader));
                 assert_eq!(postings.doc(), 3);
@@ -522,25 +544,25 @@ mod tests {
         }
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             // 0
             index_writer.add_document(doc!(text_field=>"a b"));
             // 1
             index_writer.delete_term(Term::from_field_text(text_field, "c"));
-            index_writer.rollback()?;
+            index_writer.rollback().unwrap();
         }
         {
-            reader.reload()?;
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             let seg_reader = searcher.segment_reader(0);
-            let inverted_index = seg_reader.inverted_index(term_abcd.field())?;
+            let inverted_index = seg_reader.inverted_index(term_abcd.field());
 
             assert!(inverted_index
-                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)
                 .is_none());
             {
                 let mut postings = inverted_index
-                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)?
+                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert!(advance_undeleted(&mut postings, seg_reader));
                 assert_eq!(postings.doc(), 5);
@@ -548,7 +570,7 @@ mod tests {
             }
             {
                 let mut postings = inverted_index
-                    .read_postings(&term_b, IndexRecordOption::WithFreqsAndPositions)?
+                    .read_postings(&term_b, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert!(advance_undeleted(&mut postings, seg_reader));
                 assert_eq!(postings.doc(), 3);
@@ -559,30 +581,30 @@ mod tests {
         }
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.add_document(doc!(text_field=>"a b"));
             index_writer.delete_term(Term::from_field_text(text_field, "c"));
-            index_writer.rollback()?;
+            index_writer.rollback().unwrap();
             index_writer.delete_term(Term::from_field_text(text_field, "a"));
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
         }
         {
-            reader.reload()?;
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             let segment_reader = searcher.segment_reader(0);
-            let inverted_index = segment_reader.inverted_index(term_abcd.field())?;
+            let inverted_index = segment_reader.inverted_index(term_abcd.field());
             assert!(inverted_index
-                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)
                 .is_none());
             {
                 let mut postings = inverted_index
-                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)?
+                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert!(!advance_undeleted(&mut postings, segment_reader));
             }
             {
                 let mut postings = inverted_index
-                    .read_postings(&term_b, IndexRecordOption::WithFreqsAndPositions)?
+                    .read_postings(&term_b, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert!(advance_undeleted(&mut postings, segment_reader));
                 assert_eq!(postings.doc(), 3);
@@ -592,107 +614,104 @@ mod tests {
             }
             {
                 let mut postings = inverted_index
-                    .read_postings(&term_c, IndexRecordOption::WithFreqsAndPositions)?
+                    .read_postings(&term_c, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert!(advance_undeleted(&mut postings, segment_reader));
                 assert_eq!(postings.doc(), 4);
                 assert!(!advance_undeleted(&mut postings, segment_reader));
             }
         }
-        Ok(())
     }
 
     #[test]
-    fn test_indexed_u64() -> crate::Result<()> {
+    fn test_indexed_u64() {
         let mut schema_builder = Schema::builder();
         let field = schema_builder.add_u64_field("value", INDEXED);
         let schema = schema_builder.build();
 
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(field=>1u64));
-        index_writer.commit()?;
+        index_writer.commit().unwrap();
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let term = Term::from_field_u64(field, 1u64);
         let mut postings = searcher
             .segment_reader(0)
-            .inverted_index(term.field())?
+            .inverted_index(term.field())
-            .read_postings(&term, IndexRecordOption::Basic)?
+            .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
+        assert!(postings.advance());
         assert_eq!(postings.doc(), 0);
-        assert_eq!(postings.advance(), TERMINATED);
+        assert!(!postings.advance());
-        Ok(())
     }
 
     #[test]
-    fn test_indexed_i64() -> crate::Result<()> {
+    fn test_indexed_i64() {
         let mut schema_builder = Schema::builder();
         let value_field = schema_builder.add_i64_field("value", INDEXED);
         let schema = schema_builder.build();
 
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let negative_val = -1i64;
         index_writer.add_document(doc!(value_field => negative_val));
-        index_writer.commit()?;
+        index_writer.commit().unwrap();
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let term = Term::from_field_i64(value_field, negative_val);
         let mut postings = searcher
             .segment_reader(0)
-            .inverted_index(term.field())?
+            .inverted_index(term.field())
-            .read_postings(&term, IndexRecordOption::Basic)?
+            .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
+        assert!(postings.advance());
         assert_eq!(postings.doc(), 0);
-        assert_eq!(postings.advance(), TERMINATED);
+        assert!(!postings.advance());
-        Ok(())
     }
 
     #[test]
-    fn test_indexed_f64() -> crate::Result<()> {
+    fn test_indexed_f64() {
         let mut schema_builder = Schema::builder();
         let value_field = schema_builder.add_f64_field("value", INDEXED);
         let schema = schema_builder.build();
 
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let val = std::f64::consts::PI;
         index_writer.add_document(doc!(value_field => val));
-        index_writer.commit()?;
+        index_writer.commit().unwrap();
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let term = Term::from_field_f64(value_field, val);
         let mut postings = searcher
             .segment_reader(0)
-            .inverted_index(term.field())?
+            .inverted_index(term.field())
-            .read_postings(&term, IndexRecordOption::Basic)?
+            .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
+        assert!(postings.advance());
         assert_eq!(postings.doc(), 0);
-        assert_eq!(postings.advance(), TERMINATED);
+        assert!(!postings.advance());
-        Ok(())
     }
 
     #[test]
-    fn test_indexedfield_not_in_documents() -> crate::Result<()> {
+    fn test_indexedfield_not_in_documents() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let absent_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(2, 6_000_000).unwrap();
         index_writer.add_document(doc!(text_field=>"a"));
         assert!(index_writer.commit().is_ok());
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let segment_reader = searcher.segment_reader(0);
-        let inverted_index = segment_reader.inverted_index(absent_field)?;
+        segment_reader.inverted_index(absent_field); //< should not panic
-        assert_eq!(inverted_index.terms().num_terms(), 0);
-        Ok(())
     }
 
     #[test]
-    fn test_delete_postings2() -> crate::Result<()> {
+    fn test_delete_postings2() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
@@ -700,112 +719,128 @@ mod tests {
         let reader = index
             .reader_builder()
             .reload_policy(ReloadPolicy::Manual)
-            .try_into()?;
+            .try_into()
+            .unwrap();
 
         // writing the segment
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(2, 6_000_000).unwrap();
-        index_writer.add_document(doc!(text_field=>"63"));
+
-        index_writer.add_document(doc!(text_field=>"70"));
+        let add_document = |index_writer: &mut IndexWriter, val: &'static str| {
-        index_writer.add_document(doc!(text_field=>"34"));
+            let doc = doc!(text_field=>val);
-        index_writer.add_document(doc!(text_field=>"1"));
+            index_writer.add_document(doc);
-        index_writer.add_document(doc!(text_field=>"38"));
+        };
-        index_writer.add_document(doc!(text_field=>"33"));
+
-        index_writer.add_document(doc!(text_field=>"40"));
+        let remove_document = |index_writer: &mut IndexWriter, val: &'static str| {
-        index_writer.add_document(doc!(text_field=>"17"));
+            let delterm = Term::from_field_text(text_field, val);
-        index_writer.delete_term(Term::from_field_text(text_field, "38"));
+            index_writer.delete_term(delterm);
-        index_writer.delete_term(Term::from_field_text(text_field, "34"));
+        };
-        index_writer.commit()?;
+
-        reader.reload()?;
+        add_document(&mut index_writer, "63");
-        assert_eq!(reader.searcher().num_docs(), 6);
+        add_document(&mut index_writer, "70");
-        Ok(())
+        add_document(&mut index_writer, "34");
+        add_document(&mut index_writer, "1");
+        add_document(&mut index_writer, "38");
+        add_document(&mut index_writer, "33");
+        add_document(&mut index_writer, "40");
+        add_document(&mut index_writer, "17");
+        remove_document(&mut index_writer, "38");
+        remove_document(&mut index_writer, "34");
+        index_writer.commit().unwrap();
+        reader.reload().unwrap();
+        let searcher = reader.searcher();
+        assert_eq!(searcher.num_docs(), 6);
     }
 
     #[test]
-    fn test_termfreq() -> crate::Result<()> {
+    fn test_termfreq() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-            index_writer.add_document(doc!(text_field=>"af af af bc bc"));
+            {
-            index_writer.commit()?;
+                let doc = doc!(text_field=>"af af af bc bc");
+                index_writer.add_document(doc);
+            }
+            index_writer.commit().unwrap();
         }
         {
-            let index_reader = index.reader()?;
+            let index_reader = index.reader().unwrap();
             let searcher = index_reader.searcher();
             let reader = searcher.segment_reader(0);
-            let inverted_index = reader.inverted_index(text_field)?;
+            let inverted_index = reader.inverted_index(text_field);
             let term_abcd = Term::from_field_text(text_field, "abcd");
             assert!(inverted_index
-                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term_abcd, IndexRecordOption::WithFreqsAndPositions)
                 .is_none());
             let term_af = Term::from_field_text(text_field, "af");
             let mut postings = inverted_index
-                .read_postings(&term_af, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term_af, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
+            assert!(postings.advance());
             assert_eq!(postings.doc(), 0);
             assert_eq!(postings.term_freq(), 3);
-            assert_eq!(postings.advance(), TERMINATED);
+            assert!(!postings.advance());
         }
-        Ok(())
     }
 
     #[test]
-    fn test_searcher_1() -> crate::Result<()> {
+    fn test_searcher_1() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
-        // writing the segment
+        {
-        let mut index_writer = index.writer_for_tests()?;
+            // writing the segment
-        index_writer.add_document(doc!(text_field=>"af af af b"));
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-        index_writer.add_document(doc!(text_field=>"a b c"));
+            index_writer.add_document(doc!(text_field=>"af af af b"));
-        index_writer.add_document(doc!(text_field=>"a b c d"));
+            index_writer.add_document(doc!(text_field=>"a b c"));
-        index_writer.commit()?;
+            index_writer.add_document(doc!(text_field=>"a b c d"));
-
+            index_writer.commit().unwrap();
-        reader.reload()?;
+        }
-        let searcher = reader.searcher();
+        {
-        let get_doc_ids = |terms: Vec<Term>| {
+            reader.reload().unwrap();
-            let query = BooleanQuery::new_multiterms_query(terms);
+            let searcher = reader.searcher();
-            searcher
+            let get_doc_ids = |terms: Vec<Term>| {
-                .search(&query, &TEST_COLLECTOR_WITH_SCORE)
+                let query = BooleanQuery::new_multiterms_query(terms);
-                .map(|topdocs| topdocs.docs().to_vec())
+                let topdocs = searcher.search(&query, &TEST_COLLECTOR_WITH_SCORE).unwrap();
-        };
+                topdocs.docs().to_vec()
-        assert_eq!(
+            };
-            get_doc_ids(vec![Term::from_field_text(text_field, "a")])?,
+            assert_eq!(
-            vec![DocAddress(0, 1), DocAddress(0, 2)]
+                get_doc_ids(vec![Term::from_field_text(text_field, "a")]),
-        );
+                vec![DocAddress(0, 1), DocAddress(0, 2)]
-        assert_eq!(
+            );
-            get_doc_ids(vec![Term::from_field_text(text_field, "af")])?,
+            assert_eq!(
-            vec![DocAddress(0, 0)]
+                get_doc_ids(vec![Term::from_field_text(text_field, "af")]),
-        );
+                vec![DocAddress(0, 0)]
-        assert_eq!(
+            );
-            get_doc_ids(vec![Term::from_field_text(text_field, "b")])?,
+            assert_eq!(
-            vec![DocAddress(0, 0), DocAddress(0, 1), DocAddress(0, 2)]
+                get_doc_ids(vec![Term::from_field_text(text_field, "b")]),
-        );
+                vec![DocAddress(0, 0), DocAddress(0, 1), DocAddress(0, 2)]
-        assert_eq!(
+            );
-            get_doc_ids(vec![Term::from_field_text(text_field, "c")])?,
+            assert_eq!(
-            vec![DocAddress(0, 1), DocAddress(0, 2)]
+                get_doc_ids(vec![Term::from_field_text(text_field, "c")]),
-        );
+                vec![DocAddress(0, 1), DocAddress(0, 2)]
-        assert_eq!(
+            );
-            get_doc_ids(vec![Term::from_field_text(text_field, "d")])?,
+            assert_eq!(
-            vec![DocAddress(0, 2)]
+                get_doc_ids(vec![Term::from_field_text(text_field, "d")]),
-        );
+                vec![DocAddress(0, 2)]
-        assert_eq!(
+            );
-            get_doc_ids(vec![
+            assert_eq!(
-                Term::from_field_text(text_field, "b"),
+                get_doc_ids(vec![
-                Term::from_field_text(text_field, "a"),
+                    Term::from_field_text(text_field, "b"),
-            ])?,
+                    Term::from_field_text(text_field, "a"),
-            vec![DocAddress(0, 0), DocAddress(0, 1), DocAddress(0, 2)]
+                ]),
-        );
+                vec![DocAddress(0, 0), DocAddress(0, 1), DocAddress(0, 2)]
-        Ok(())
+            );
+        }
     }
 
     #[test]
-    fn test_searcher_2() -> crate::Result<()> {
+    fn test_searcher_2() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
@@ -813,17 +848,19 @@ mod tests {
         let reader = index
             .reader_builder()
             .reload_policy(ReloadPolicy::Manual)
-            .try_into()?;
+            .try_into()
+            .unwrap();
         assert_eq!(reader.searcher().num_docs(), 0u64);
-        // writing the segment
+        {
-        let mut index_writer = index.writer_for_tests()?;
+            // writing the segment
-        index_writer.add_document(doc!(text_field=>"af b"));
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
-        index_writer.add_document(doc!(text_field=>"a b c"));
+            index_writer.add_document(doc!(text_field=>"af b"));
-        index_writer.add_document(doc!(text_field=>"a b c d"));
+            index_writer.add_document(doc!(text_field=>"a b c"));
-        index_writer.commit()?;
+            index_writer.add_document(doc!(text_field=>"a b c d"));
-        reader.reload()?;
+            index_writer.commit().unwrap();
+        }
+        reader.reload().unwrap();
         assert_eq!(reader.searcher().num_docs(), 3u64);
-        Ok(())
     }
 
     #[test]
@@ -835,17 +872,17 @@ mod tests {
                             text_field => "some other value",
                             other_text_field => "short");
         assert_eq!(document.len(), 3);
-        let values: Vec<&Value> = document.get_all(text_field).collect();
+        let values = document.get_all(text_field);
         assert_eq!(values.len(), 2);
         assert_eq!(values[0].text(), Some("tantivy"));
         assert_eq!(values[1].text(), Some("some other value"));
-        let values: Vec<&Value> = document.get_all(other_text_field).collect();
+        let values = document.get_all(other_text_field);
         assert_eq!(values.len(), 1);
         assert_eq!(values[0].text(), Some("short"));
     }
 
     #[test]
-    fn test_wrong_fast_field_type() -> crate::Result<()> {
+    fn test_wrong_fast_field_type() {
         let mut schema_builder = Schema::builder();
         let fast_field_unsigned = schema_builder.add_u64_field("unsigned", FAST);
         let fast_field_signed = schema_builder.add_i64_field("signed", FAST);
@@ -855,14 +892,14 @@ mod tests {
         let schema = schema_builder.build();
 
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 50_000_000).unwrap();
         {
             let document =
                 doc!(fast_field_unsigned => 4u64, fast_field_signed=>4i64, fast_field_float=>4f64);
             index_writer.add_document(document);
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
         }
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let segment_reader: &SegmentReader = searcher.segment_reader(0);
         {
@@ -901,12 +938,11 @@ mod tests {
             let fast_field_reader = fast_field_reader_opt.unwrap();
             assert_eq!(fast_field_reader.get(0), 4f64)
         }
-        Ok(())
     }
 
     // motivated by #729
     #[test]
-    fn test_update_via_delete_insert() -> crate::Result<()> {
+    fn test_update_via_delete_insert() {
         use crate::collector::Count;
         use crate::indexer::NoMergePolicy;
         use crate::query::AllQuery;
@@ -920,17 +956,17 @@ mod tests {
         let schema = schema_builder.build();
 
         let index = Index::create_in_ram(schema.clone());
-        let index_reader = index.reader()?;
+        let index_reader = index.reader().unwrap();
 
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer(3_000_000).unwrap();
         index_writer.set_merge_policy(Box::new(NoMergePolicy));
 
         for doc_id in 0u64..DOC_COUNT {
             index_writer.add_document(doc!(id => doc_id));
         }
-        index_writer.commit()?;
+        index_writer.commit().unwrap();
 
-        index_reader.reload()?;
+        index_reader.reload().unwrap();
         let searcher = index_reader.searcher();
 
         assert_eq!(
@@ -941,11 +977,12 @@ mod tests {
         // update the 10 elements by deleting and re-adding
         for doc_id in 0u64..DOC_COUNT {
             index_writer.delete_term(Term::from_field_u64(id, doc_id));
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
-            index_reader.reload()?;
+            index_reader.reload().unwrap();
-            index_writer.add_document(doc!(id =>  doc_id));
+            let doc = doc!(id =>  doc_id);
-            index_writer.commit()?;
+            index_writer.add_document(doc);
-            index_reader.reload()?;
+            index_writer.commit().unwrap();
+            index_reader.reload().unwrap();
             let searcher = index_reader.searcher();
             // The number of document should be stable.
             assert_eq!(
@@ -954,7 +991,7 @@ mod tests {
             );
         }
 
-        index_reader.reload()?;
+        index_reader.reload().unwrap();
         let searcher = index_reader.searcher();
         let segment_ids: Vec<SegmentId> = searcher
             .segment_readers()
@@ -963,18 +1000,12 @@ mod tests {
             .collect();
         block_on(index_writer.merge(&segment_ids)).unwrap();
 
-        index_reader.reload()?;
+        index_reader.reload().unwrap();
         let searcher = index_reader.searcher();
-        assert_eq!(searcher.search(&AllQuery, &Count)?, DOC_COUNT as usize);
-        Ok(())
-    }
 
-    #[test]
+        assert_eq!(
-    fn test_validate_checksum() -> crate::Result<()> {
+            searcher.search(&AllQuery, &Count).unwrap(),
-        let index_path = tempfile::tempdir().expect("dir");
+            DOC_COUNT as usize
-        let schema = Schema::builder().build();
+        );
-        let index = Index::create_in_dir(&index_path, schema)?;
-        assert!(index.validate_checksum()?.is_empty());
-        Ok(())
     }
 }

src/positions/mod.rs

@@ -37,12 +37,12 @@ const LONG_SKIP_INTERVAL: u64 = (LONG_SKIP_IN_BLOCKS * COMPRESSION_BLOCK_SIZE) a
 #[cfg(test)]
 pub mod tests {
 
-    use super::PositionSerializer;
+    use super::{PositionReader, PositionSerializer};
-    use crate::positions::reader::PositionReader;
+    use crate::directory::ReadOnlySource;
-    use crate::{common::HasLen, directory::FileSlice};
+    use crate::positions::COMPRESSION_BLOCK_SIZE;
     use std::iter;
 
-    fn create_stream_buffer(vals: &[u32]) -> (FileSlice, FileSlice) {
+    fn create_stream_buffer(vals: &[u32]) -> (ReadOnlySource, ReadOnlySource) {
         let mut skip_buffer = vec![];
         let mut stream_buffer = vec![];
         {
@@ -53,7 +53,10 @@ pub mod tests {
             }
             serializer.close().unwrap();
         }
-        (FileSlice::from(stream_buffer), FileSlice::from(skip_buffer))
+        (
+            ReadOnlySource::from(stream_buffer),
+            ReadOnlySource::from(skip_buffer),
+        )
     }
 
     #[test]
@@ -62,10 +65,10 @@ pub mod tests {
         let (stream, skip) = create_stream_buffer(&v[..]);
         assert_eq!(skip.len(), 12);
         assert_eq!(stream.len(), 1168);
-        let mut position_reader = PositionReader::new(stream, skip, 0u64).unwrap();
+        let mut position_reader = PositionReader::new(stream, skip, 0u64);
         for &n in &[1, 10, 127, 128, 130, 312] {
             let mut v = vec![0u32; n];
-            position_reader.read(0, &mut v[..]);
+            position_reader.read(&mut v[..n]);
             for i in 0..n {
                 assert_eq!(v[i], i as u32);
             }
@@ -73,19 +76,19 @@ pub mod tests {
     }
 
     #[test]
-    fn test_position_read_with_offset() {
+    fn test_position_skip() {
-        let v: Vec<u32> = (0..1000).collect();
+        let v: Vec<u32> = (0..1_000).collect();
         let (stream, skip) = create_stream_buffer(&v[..]);
         assert_eq!(skip.len(), 12);
         assert_eq!(stream.len(), 1168);
-        let mut position_reader = PositionReader::new(stream, skip, 0u64).unwrap();
+
-        for &offset in &[1u64, 10u64, 127u64, 128u64, 130u64, 312u64] {
+        let mut position_reader = PositionReader::new(stream, skip, 0u64);
-            for &len in &[1, 10, 130, 500] {
+        position_reader.skip(10);
-                let mut v = vec![0u32; len];
+        for &n in &[10, 127, COMPRESSION_BLOCK_SIZE, 130, 312] {
-                position_reader.read(offset, &mut v[..]);
+            let mut v = vec![0u32; n];
-                for i in 0..len {
+            position_reader.read(&mut v[..n]);
-                    assert_eq!(v[i], i as u32 + offset as u32);
+            for i in 0..n {
-                }
+                assert_eq!(v[i], 10u32 + i as u32);
             }
         }
     }
@@ -97,15 +100,14 @@ pub mod tests {
         assert_eq!(skip.len(), 12);
         assert_eq!(stream.len(), 1168);
 
-        let mut position_reader = PositionReader::new(stream, skip, 0u64).unwrap();
+        let mut position_reader = PositionReader::new(stream, skip, 0u64);
         let mut buf = [0u32; 7];
         let mut c = 0;
-
-        let mut offset = 0;
         for _ in 0..100 {
-            position_reader.read(offset, &mut buf);
+            position_reader.read(&mut buf);
-            position_reader.read(offset, &mut buf);
+            position_reader.read(&mut buf);
-            offset += 7;
+            position_reader.skip(4);
+            position_reader.skip(3);
             for &el in &buf {
                 assert_eq!(c, el);
                 c += 1;
@@ -113,59 +115,6 @@ pub mod tests {
         }
     }
 
-    #[test]
-    fn test_position_reread_anchor_different_than_block() {
-        let v: Vec<u32> = (0..2_000_000).collect();
-        let (stream, skip) = create_stream_buffer(&v[..]);
-        assert_eq!(skip.len(), 15_749);
-        assert_eq!(stream.len(), 4_987_872);
-        let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), 0).unwrap();
-        let mut buf = [0u32; 256];
-        position_reader.read(128, &mut buf);
-        for i in 0..256 {
-            assert_eq!(buf[i], (128 + i) as u32);
-        }
-        position_reader.read(128, &mut buf);
-        for i in 0..256 {
-            assert_eq!(buf[i], (128 + i) as u32);
-        }
-    }
-
-    #[test]
-    #[should_panic(expected = "offset arguments should be increasing.")]
-    fn test_position_panic_if_called_previous_anchor() {
-        let v: Vec<u32> = (0..2_000_000).collect();
-        let (stream, skip) = create_stream_buffer(&v[..]);
-        assert_eq!(skip.len(), 15_749);
-        assert_eq!(stream.len(), 4_987_872);
-        let mut buf = [0u32; 1];
-        let mut position_reader =
-            PositionReader::new(stream.clone(), skip.clone(), 200_000).unwrap();
-        position_reader.read(230, &mut buf);
-        position_reader.read(9, &mut buf);
-    }
-
-    #[test]
-    fn test_positions_bug() {
-        let mut v: Vec<u32> = vec![];
-        for i in 1..200 {
-            for j in 0..i {
-                v.push(j);
-            }
-        }
-        let (stream, skip) = create_stream_buffer(&v[..]);
-        let mut buf = Vec::new();
-        let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), 0).unwrap();
-        let mut offset = 0;
-        for i in 1..24 {
-            buf.resize(i, 0);
-            position_reader.read(offset, &mut buf[..]);
-            offset += i as u64;
-            let r: Vec<u32> = (0..i).map(|el| el as u32).collect();
-            assert_eq!(buf, &r[..]);
-        }
-    }
-
     #[test]
     fn test_position_long_skip_const() {
         const CONST_VAL: u32 = 9u32;
@@ -173,9 +122,9 @@ pub mod tests {
         let (stream, skip) = create_stream_buffer(&v[..]);
         assert_eq!(skip.len(), 15_749);
         assert_eq!(stream.len(), 1_000_000);
-        let mut position_reader = PositionReader::new(stream, skip, 128 * 1024).unwrap();
+        let mut position_reader = PositionReader::new(stream, skip, 128 * 1024);
         let mut buf = [0u32; 1];
-        position_reader.read(0, &mut buf);
+        position_reader.read(&mut buf);
         assert_eq!(buf[0], CONST_VAL);
     }
 
@@ -192,10 +141,9 @@ pub mod tests {
             128 * 1024 + 7,
             128 * 10 * 1024 + 10,
         ] {
-            let mut position_reader =
+            let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), offset);
-                PositionReader::new(stream.clone(), skip.clone(), offset).unwrap();
             let mut buf = [0u32; 1];
-            position_reader.read(0, &mut buf);
+            position_reader.read(&mut buf);
             assert_eq!(buf[0], offset as u32);
         }
     }

src/positions/reader.rs

@@ -1,13 +1,9 @@
-use std::io;
-
 use crate::common::{BinarySerializable, FixedSize};
-use crate::directory::FileSlice;
+use crate::directory::ReadOnlySource;
-use crate::directory::OwnedBytes;
 use crate::positions::COMPRESSION_BLOCK_SIZE;
 use crate::positions::LONG_SKIP_INTERVAL;
 use crate::positions::LONG_SKIP_IN_BLOCKS;
-use bitpacking::{BitPacker, BitPacker4x};
+use crate::postings::compression::compressed_block_size;
-
 /// Positions works as a long sequence of compressed block.
 /// All terms are chained one after the other.
 ///
@@ -28,28 +24,28 @@ use bitpacking::{BitPacker, BitPacker4x};
 /// A given block obviously takes `(128 x  num_bit_for_the_block / num_bits_in_a_byte)`,
 /// so skipping a block without decompressing it is just a matter of advancing that many
 /// bytes.
+use bitpacking::{BitPacker, BitPacker4x};
+use owned_read::OwnedRead;
 
 struct Positions {
     bit_packer: BitPacker4x,
-    skip_file: FileSlice,
+    skip_source: ReadOnlySource,
-    position_file: FileSlice,
+    position_source: ReadOnlySource,
-    long_skip_data: OwnedBytes,
+    long_skip_source: ReadOnlySource,
 }
 
 impl Positions {
-    pub fn new(position_file: FileSlice, skip_file: FileSlice) -> io::Result<Positions> {
+    pub fn new(position_source: ReadOnlySource, skip_source: ReadOnlySource) -> Positions {
-        let (body, footer) = skip_file.split_from_end(u32::SIZE_IN_BYTES);
+        let (body, footer) = skip_source.split_from_end(u32::SIZE_IN_BYTES);
-        let footer_data = footer.read_bytes()?;
+        let num_long_skips = u32::deserialize(&mut footer.as_slice()).expect("Index corrupted");
-        let num_long_skips = u32::deserialize(&mut footer_data.as_slice())?;
+        let (skip_source, long_skip_source) =
-        let (skip_file, long_skip_file) =
             body.split_from_end(u64::SIZE_IN_BYTES * (num_long_skips as usize));
-        let long_skip_data = long_skip_file.read_bytes()?;
+        Positions {
-        Ok(Positions {
             bit_packer: BitPacker4x::new(),
-            skip_file,
+            skip_source,
-            long_skip_data,
+            long_skip_source,
-            position_file,
+            position_source,
-        })
+        }
     }
 
     /// Returns the offset of the block associated to the given `long_skip_id`.
@@ -59,116 +55,143 @@ impl Positions {
         if long_skip_id == 0 {
             return 0;
         }
-        let long_skip_slice = self.long_skip_data.as_slice();
+        let long_skip_slice = self.long_skip_source.as_slice();
         let mut long_skip_blocks: &[u8] = &long_skip_slice[(long_skip_id - 1) * 8..][..8];
         u64::deserialize(&mut long_skip_blocks).expect("Index corrupted")
     }
 
-    fn reader(&self, offset: u64) -> io::Result<PositionReader> {
+    fn reader(&self, offset: u64) -> PositionReader {
         let long_skip_id = (offset / LONG_SKIP_INTERVAL) as usize;
+        let small_skip = (offset % LONG_SKIP_INTERVAL) as usize;
         let offset_num_bytes: u64 = self.long_skip(long_skip_id);
-        let position_read = self
+        let mut position_read = OwnedRead::new(self.position_source.clone());
-            .position_file
+        position_read.advance(offset_num_bytes as usize);
-            .slice_from(offset_num_bytes as usize)
+        let mut skip_read = OwnedRead::new(self.skip_source.clone());
-            .read_bytes()?;
+        skip_read.advance(long_skip_id * LONG_SKIP_IN_BLOCKS);
-        let skip_read = self
+        let mut position_reader = PositionReader {
-            .skip_file
-            .slice_from(long_skip_id * LONG_SKIP_IN_BLOCKS)
-            .read_bytes()?;
-        Ok(PositionReader {
             bit_packer: self.bit_packer,
             skip_read,
             position_read,
+            inner_offset: 0,
             buffer: Box::new([0u32; 128]),
-            block_offset: std::i64::MAX as u64,
+            ahead: None,
-            anchor_offset: (long_skip_id as u64) * LONG_SKIP_INTERVAL,
+        };
-            abs_offset: offset,
+        position_reader.skip(small_skip);
-        })
+        position_reader
     }
 }
 
-#[derive(Clone)]
 pub struct PositionReader {
-    skip_read: OwnedBytes,
+    skip_read: OwnedRead,
-    position_read: OwnedBytes,
+    position_read: OwnedRead,
     bit_packer: BitPacker4x,
-    buffer: Box<[u32; COMPRESSION_BLOCK_SIZE]>,
+    inner_offset: usize,
+    buffer: Box<[u32; 128]>,
+    ahead: Option<usize>, // if None, no block is loaded.
+                          // if Some(num_blocks), the block currently loaded is num_blocks ahead
+                          // of the block of the next int to read.
+}
 
-    block_offset: u64,
+// `ahead` represents the offset of the block currently loaded
-    anchor_offset: u64,
+// compared to the cursor of the actual stream.
-
+//
-    abs_offset: u64,
+// By contract, when this function is called, the current block has to be
+// decompressed.
+//
+// If the requested number of els ends exactly at a given block, the next
+// block is not decompressed.
+fn read_impl(
+    bit_packer: BitPacker4x,
+    mut position: &[u8],
+    buffer: &mut [u32; 128],
+    mut inner_offset: usize,
+    num_bits: &[u8],
+    output: &mut [u32],
+) -> usize {
+    let mut output_start = 0;
+    let mut output_len = output.len();
+    let mut ahead = 0;
+    loop {
+        let available_len = COMPRESSION_BLOCK_SIZE - inner_offset;
+        // We have enough elements in the current block.
+        // Let's copy the requested elements in the output buffer,
+        // and return.
+        if output_len <= available_len {
+            output[output_start..].copy_from_slice(&buffer[inner_offset..][..output_len]);
+            return ahead;
+        }
+        output[output_start..][..available_len].copy_from_slice(&buffer[inner_offset..]);
+        output_len -= available_len;
+        output_start += available_len;
+        inner_offset = 0;
+        let num_bits = num_bits[ahead];
+        bit_packer.decompress(position, &mut buffer[..], num_bits);
+        let block_len = compressed_block_size(num_bits);
+        position = &position[block_len..];
+        ahead += 1;
+    }
 }
 
 impl PositionReader {
     pub fn new(
-        position_file: FileSlice,
+        position_source: ReadOnlySource,
-        skip_file: FileSlice,
+        skip_source: ReadOnlySource,
         offset: u64,
-    ) -> io::Result<PositionReader> {
+    ) -> PositionReader {
-        let positions = Positions::new(position_file, skip_file)?;
+        Positions::new(position_source, skip_source).reader(offset)
-        positions.reader(offset)
     }
 
-    fn advance_num_blocks(&mut self, num_blocks: usize) {
+    /// Fills a buffer with the next `output.len()` integers.
-        let num_bits: usize = self.skip_read.as_ref()[..num_blocks]
+    /// This does not consume / advance the stream.
-            .iter()
+    pub fn read(&mut self, output: &mut [u32]) {
-            .cloned()
+        let skip_data = self.skip_read.as_ref();
-            .map(|num_bits| num_bits as usize)
+        let position_data = self.position_read.as_ref();
-            .sum();
+        let num_bits = self.skip_read.get(0);
-        let num_bytes_to_skip = num_bits * COMPRESSION_BLOCK_SIZE / 8;
+        if self.ahead != Some(0) {
-        self.skip_read.advance(num_blocks as usize);
+            // the block currently available is not the block
-        self.position_read.advance(num_bytes_to_skip);
+            // for the current position
-    }
-
-    /// Fills a buffer with the positions `[offset..offset+output.len())` integers.
-    ///
-    /// `offset` is required to have a value >= to the offsets given in previous calls
-    /// for the given `PositionReaderAbsolute` instance.
-    pub fn read(&mut self, mut offset: u64, mut output: &mut [u32]) {
-        offset += self.abs_offset;
-        assert!(
-            offset >= self.anchor_offset,
-            "offset arguments should be increasing."
-        );
-        let delta_to_block_offset = offset as i64 - self.block_offset as i64;
-        if delta_to_block_offset < 0 || delta_to_block_offset >= 128 {
-            // The first position is not within the first block.
-            // We need to decompress the first block.
-            let delta_to_anchor_offset = offset - self.anchor_offset;
-            let num_blocks_to_skip =
-                (delta_to_anchor_offset / (COMPRESSION_BLOCK_SIZE as u64)) as usize;
-            self.advance_num_blocks(num_blocks_to_skip);
-            self.anchor_offset = offset - (offset % COMPRESSION_BLOCK_SIZE as u64);
-            self.block_offset = self.anchor_offset;
-            let num_bits = self.skip_read.as_slice()[0];
-            self.bit_packer
-                .decompress(self.position_read.as_ref(), self.buffer.as_mut(), num_bits);
-        } else {
-            let num_blocks_to_skip =
-                ((self.block_offset - self.anchor_offset) / COMPRESSION_BLOCK_SIZE as u64) as usize;
-            self.advance_num_blocks(num_blocks_to_skip);
-            self.anchor_offset = self.block_offset;
-        }
-
-        let mut num_bits = self.skip_read.as_slice()[0];
-        let mut position_data = self.position_read.as_ref();
-
-        for i in 1.. {
-            let offset_in_block = (offset as usize) % COMPRESSION_BLOCK_SIZE;
-            let remaining_in_block = COMPRESSION_BLOCK_SIZE - offset_in_block;
-            if remaining_in_block >= output.len() {
-                output.copy_from_slice(&self.buffer[offset_in_block..][..output.len()]);
-                break;
-            }
-            output[..remaining_in_block].copy_from_slice(&self.buffer[offset_in_block..]);
-            output = &mut output[remaining_in_block..];
-            offset += remaining_in_block as u64;
-            position_data = &position_data[(num_bits as usize * COMPRESSION_BLOCK_SIZE / 8)..];
-            num_bits = self.skip_read.as_slice()[i];
             self.bit_packer
                 .decompress(position_data, self.buffer.as_mut(), num_bits);
-            self.block_offset += COMPRESSION_BLOCK_SIZE as u64;
+            self.ahead = Some(0);
         }
+        let block_len = compressed_block_size(num_bits);
+        self.ahead = Some(read_impl(
+            self.bit_packer,
+            &position_data[block_len..],
+            self.buffer.as_mut(),
+            self.inner_offset,
+            &skip_data[1..],
+            output,
+        ));
+    }
+
+    /// Skip the next `skip_len` integer.
+    ///
+    /// If a full block is skipped, calling
+    /// `.skip(...)` will avoid decompressing it.
+    ///
+    /// May panic if the end of the stream is reached.
+    pub fn skip(&mut self, skip_len: usize) {
+        let skip_len_plus_inner_offset = skip_len + self.inner_offset;
+
+        let num_blocks_to_advance = skip_len_plus_inner_offset / COMPRESSION_BLOCK_SIZE;
+        self.inner_offset = skip_len_plus_inner_offset % COMPRESSION_BLOCK_SIZE;
+
+        self.ahead = self.ahead.and_then(|num_blocks| {
+            if num_blocks >= num_blocks_to_advance {
+                Some(num_blocks - num_blocks_to_advance)
+            } else {
+                None
+            }
+        });
+
+        let skip_len_in_bits = self.skip_read.as_ref()[..num_blocks_to_advance]
+            .iter()
+            .map(|num_bits| *num_bits as usize)
+            .sum::<usize>()
+            * COMPRESSION_BLOCK_SIZE;
+        let skip_len_in_bytes = skip_len_in_bits / 8;
+        self.skip_read.advance(num_blocks_to_advance);
+        self.position_read.advance(skip_len_in_bytes);
     }
 }

src/positions/serializer.rs

@@ -8,7 +8,7 @@ use std::io::{self, Write};
 pub struct PositionSerializer<W: io::Write> {
     bit_packer: BitPacker4x,
     write_stream: CountingWriter<W>,
-    write_skip_index: W,
+    write_skiplist: W,
     block: Vec<u32>,
     buffer: Vec<u8>,
     num_ints: u64,
@@ -16,11 +16,11 @@ pub struct PositionSerializer<W: io::Write> {
 }
 
 impl<W: io::Write> PositionSerializer<W> {
-    pub fn new(write_stream: W, write_skip_index: W) -> PositionSerializer<W> {
+    pub fn new(write_stream: W, write_skiplist: W) -> PositionSerializer<W> {
         PositionSerializer {
             bit_packer: BitPacker4x::new(),
             write_stream: CountingWriter::wrap(write_stream),
-            write_skip_index,
+            write_skiplist,
             block: Vec::with_capacity(128),
             buffer: vec![0u8; 128 * 4],
             num_ints: 0u64,
@@ -52,7 +52,7 @@ impl<W: io::Write> PositionSerializer<W> {
 
     fn flush_block(&mut self) -> io::Result<()> {
         let num_bits = self.bit_packer.num_bits(&self.block[..]);
-        self.write_skip_index.write_all(&[num_bits])?;
+        self.write_skiplist.write_all(&[num_bits])?;
         let written_len = self
             .bit_packer
             .compress(&self.block[..], &mut self.buffer, num_bits);
@@ -70,10 +70,10 @@ impl<W: io::Write> PositionSerializer<W> {
             self.flush_block()?;
         }
         for &long_skip in &self.long_skips {
-            long_skip.serialize(&mut self.write_skip_index)?;
+            long_skip.serialize(&mut self.write_skiplist)?;
         }
-        (self.long_skips.len() as u32).serialize(&mut self.write_skip_index)?;
+        (self.long_skips.len() as u32).serialize(&mut self.write_skiplist)?;
-        self.write_skip_index.flush()?;
+        self.write_skiplist.flush()?;
         self.write_stream.flush()?;
         Ok(())
     }

src/postings/block_search.rs

@@ -87,7 +87,6 @@ fn exponential_search(arr: &[u32], target: u32) -> (usize, usize) {
     (begin, end)
 }
 
-#[inline(never)]
 fn galloping(block_docs: &[u32], target: u32) -> usize {
     let (start, end) = exponential_search(&block_docs, target);
     start + linear_search(&block_docs[start..end], target)
@@ -130,18 +129,23 @@ impl BlockSearcher {
     ///
     /// If SSE2 instructions are available in the `(platform, running CPU)`,
     /// then we use a different implementation that does an exhaustive linear search over
-    /// the block regardless of whether the block is full or not.
+    /// the full block whenever the block is full (`len == 128`). It is surprisingly faster, most likely because of the lack
-    ///
+    /// of branch.
-    /// Indeed, if the block is not full, the remaining items are TERMINATED.
+    pub(crate) fn search_in_block(
-    /// It is surprisingly faster, most likely because of the lack of branch misprediction.
+        self,
-    pub(crate) fn search_in_block(self, block_docs: &AlignedBuffer, target: u32) -> usize {
+        block_docs: &AlignedBuffer,
+        len: usize,
+        start: usize,
+        target: u32,
+    ) -> usize {
         #[cfg(target_arch = "x86_64")]
         {
-            if self == BlockSearcher::SSE2 {
+            use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
+            if self == BlockSearcher::SSE2 && len == COMPRESSION_BLOCK_SIZE {
                 return sse2::linear_search_sse2_128(block_docs, target);
             }
         }
-        galloping(&block_docs.0[..], target)
+        start + galloping(&block_docs.0[start..len], target)
     }
 }
 
@@ -162,7 +166,6 @@ mod tests {
     use super::exponential_search;
     use super::linear_search;
     use super::BlockSearcher;
-    use crate::docset::TERMINATED;
     use crate::postings::compression::{AlignedBuffer, COMPRESSION_BLOCK_SIZE};
 
     #[test]
@@ -193,12 +196,19 @@ mod tests {
     fn util_test_search_in_block(block_searcher: BlockSearcher, block: &[u32], target: u32) {
         let cursor = search_in_block_trivial_but_slow(block, target);
         assert!(block.len() < COMPRESSION_BLOCK_SIZE);
-        let mut output_buffer = [TERMINATED; COMPRESSION_BLOCK_SIZE];
+        let mut output_buffer = [u32::max_value(); COMPRESSION_BLOCK_SIZE];
         output_buffer[..block.len()].copy_from_slice(block);
-        assert_eq!(
+        for i in 0..cursor {
-            block_searcher.search_in_block(&AlignedBuffer(output_buffer), target),
+            assert_eq!(
-            cursor
+                block_searcher.search_in_block(
-        );
+                    &AlignedBuffer(output_buffer),
+                    block.len(),
+                    i,
+                    target
+                ),
+                cursor
+            );
+        }
     }
 
     fn util_test_search_in_block_all(block_searcher: BlockSearcher, block: &[u32]) {

src/postings/block_segment_postings.rs

@@ -1,530 +0,0 @@
-use std::io;
-
-use crate::common::{BinarySerializable, VInt};
-use crate::directory::FileSlice;
-use crate::directory::OwnedBytes;
-use crate::fieldnorm::FieldNormReader;
-use crate::postings::compression::{
-    AlignedBuffer, BlockDecoder, VIntDecoder, COMPRESSION_BLOCK_SIZE,
-};
-use crate::postings::{BlockInfo, FreqReadingOption, SkipReader};
-use crate::query::BM25Weight;
-use crate::schema::IndexRecordOption;
-use crate::{DocId, Score, TERMINATED};
-
-fn max_score<I: Iterator<Item = Score>>(mut it: I) -> Option<Score> {
-    if let Some(first) = it.next() {
-        Some(it.fold(first, Score::max))
-    } else {
-        None
-    }
-}
-
-/// `BlockSegmentPostings` is a cursor iterating over blocks
-/// of documents.
-///
-/// # Warning
-///
-/// While it is useful for some very specific high-performance
-/// use cases, you should prefer using `SegmentPostings` for most usage.
-#[derive(Clone)]
-pub struct BlockSegmentPostings {
-    pub(crate) doc_decoder: BlockDecoder,
-    loaded_offset: usize,
-    freq_decoder: BlockDecoder,
-    freq_reading_option: FreqReadingOption,
-    block_max_score_cache: Option<Score>,
-
-    doc_freq: u32,
-
-    data: OwnedBytes,
-    pub(crate) skip_reader: SkipReader,
-}
-
-fn decode_bitpacked_block(
-    doc_decoder: &mut BlockDecoder,
-    freq_decoder_opt: Option<&mut BlockDecoder>,
-    data: &[u8],
-    doc_offset: DocId,
-    doc_num_bits: u8,
-    tf_num_bits: u8,
-) {
-    let num_consumed_bytes = doc_decoder.uncompress_block_sorted(data, doc_offset, doc_num_bits);
-    if let Some(freq_decoder) = freq_decoder_opt {
-        freq_decoder.uncompress_block_unsorted(&data[num_consumed_bytes..], tf_num_bits);
-    }
-}
-
-fn decode_vint_block(
-    doc_decoder: &mut BlockDecoder,
-    freq_decoder_opt: Option<&mut BlockDecoder>,
-    data: &[u8],
-    doc_offset: DocId,
-    num_vint_docs: usize,
-) {
-    let num_consumed_bytes =
-        doc_decoder.uncompress_vint_sorted(data, doc_offset, num_vint_docs, TERMINATED);
-    if let Some(freq_decoder) = freq_decoder_opt {
-        freq_decoder.uncompress_vint_unsorted(
-            &data[num_consumed_bytes..],
-            num_vint_docs,
-            TERMINATED,
-        );
-    }
-}
-
-fn split_into_skips_and_postings(
-    doc_freq: u32,
-    mut bytes: OwnedBytes,
-) -> (Option<OwnedBytes>, OwnedBytes) {
-    if doc_freq < COMPRESSION_BLOCK_SIZE as u32 {
-        return (None, bytes);
-    }
-    let skip_len = VInt::deserialize(&mut bytes).expect("Data corrupted").0 as usize;
-    let (skip_data, postings_data) = bytes.split(skip_len);
-    (Some(skip_data), postings_data)
-}
-
-impl BlockSegmentPostings {
-    pub(crate) fn open(
-        doc_freq: u32,
-        data: FileSlice,
-        record_option: IndexRecordOption,
-        requested_option: IndexRecordOption,
-    ) -> io::Result<BlockSegmentPostings> {
-        let freq_reading_option = match (record_option, requested_option) {
-            (IndexRecordOption::Basic, _) => FreqReadingOption::NoFreq,
-            (_, IndexRecordOption::Basic) => FreqReadingOption::SkipFreq,
-            (_, _) => FreqReadingOption::ReadFreq,
-        };
-
-        let (skip_data_opt, postings_data) =
-            split_into_skips_and_postings(doc_freq, data.read_bytes()?);
-        let skip_reader = match skip_data_opt {
-            Some(skip_data) => SkipReader::new(skip_data, doc_freq, record_option),
-            None => SkipReader::new(OwnedBytes::empty(), doc_freq, record_option),
-        };
-
-        let mut block_segment_postings = BlockSegmentPostings {
-            doc_decoder: BlockDecoder::with_val(TERMINATED),
-            loaded_offset: std::usize::MAX,
-            freq_decoder: BlockDecoder::with_val(1),
-            freq_reading_option,
-            block_max_score_cache: None,
-            doc_freq,
-            data: postings_data,
-            skip_reader,
-        };
-        block_segment_postings.load_block();
-        Ok(block_segment_postings)
-    }
-
-    /// Returns the block_max_score for the current block.
-    /// It does not require the block to be loaded. For instance, it is ok to call this method
-    /// after having called `.shallow_advance(..)`.
-    ///
-    /// See `TermScorer::block_max_score(..)` for more information.
-    pub fn block_max_score(
-        &mut self,
-        fieldnorm_reader: &FieldNormReader,
-        bm25_weight: &BM25Weight,
-    ) -> Score {
-        if let Some(score) = self.block_max_score_cache {
-            return score;
-        }
-        if let Some(skip_reader_max_score) = self.skip_reader.block_max_score(bm25_weight) {
-            // if we are on a full block, the skip reader should have the block max information
-            // for us
-            self.block_max_score_cache = Some(skip_reader_max_score);
-            return skip_reader_max_score;
-        }
-        // this is the last block of the segment posting list.
-        // If it is actually loaded, we can compute block max manually.
-        if self.block_is_loaded() {
-            let docs = self.doc_decoder.output_array().iter().cloned();
-            let freqs = self.freq_decoder.output_array().iter().cloned();
-            let bm25_scores = docs.zip(freqs).map(|(doc, term_freq)| {
-                let fieldnorm_id = fieldnorm_reader.fieldnorm_id(doc);
-                bm25_weight.score(fieldnorm_id, term_freq)
-            });
-            let block_max_score = max_score(bm25_scores).unwrap_or(0.0);
-            self.block_max_score_cache = Some(block_max_score);
-            return block_max_score;
-        }
-        // We do not have access to any good block max value. We return bm25_weight.max_score()
-        // as it is a valid upperbound.
-        //
-        // We do not cache it however, so that it gets computed when once block is loaded.
-        bm25_weight.max_score()
-    }
-
-    pub(crate) fn freq_reading_option(&self) -> FreqReadingOption {
-        self.freq_reading_option
-    }
-
-    // Resets the block segment postings on another position
-    // in the postings file.
-    //
-    // This is useful for enumerating through a list of terms,
-    // and consuming the associated posting lists while avoiding
-    // reallocating a `BlockSegmentPostings`.
-    //
-    // # Warning
-    //
-    // This does not reset the positions list.
-    pub(crate) fn reset(&mut self, doc_freq: u32, postings_data: OwnedBytes) {
-        let (skip_data_opt, postings_data) = split_into_skips_and_postings(doc_freq, postings_data);
-        self.data = postings_data;
-        self.block_max_score_cache = None;
-        self.loaded_offset = std::usize::MAX;
-        if let Some(skip_data) = skip_data_opt {
-            self.skip_reader.reset(skip_data, doc_freq);
-        } else {
-            self.skip_reader.reset(OwnedBytes::empty(), doc_freq);
-        }
-        self.doc_freq = doc_freq;
-        self.load_block();
-    }
-
-    /// Returns the overall number of documents in the block postings.
-    /// It does not take in account whether documents are deleted or not.
-    ///
-    /// This `doc_freq` is simply the sum of the length of all of the blocks
-    /// length, and it does not take in account deleted documents.
-    pub fn doc_freq(&self) -> u32 {
-        self.doc_freq
-    }
-
-    /// Returns the array of docs in the current block.
-    ///
-    /// Before the first call to `.advance()`, the block
-    /// returned by `.docs()` is empty.
-    #[inline]
-    pub fn docs(&self) -> &[DocId] {
-        debug_assert!(self.block_is_loaded());
-        self.doc_decoder.output_array()
-    }
-
-    /// Returns a full block, regardless of whetehr the block is complete or incomplete (
-    /// as it happens for the last block of the posting list).
-    ///
-    /// In the latter case, the block is guaranteed to be padded with the sentinel value:
-    /// `TERMINATED`. The array is also guaranteed to be aligned on 16 bytes = 128 bits.
-    ///
-    /// This method is useful to run SSE2 linear search.
-    #[inline(always)]
-    pub(crate) fn docs_aligned(&self) -> &AlignedBuffer {
-        debug_assert!(self.block_is_loaded());
-        self.doc_decoder.output_aligned()
-    }
-
-    /// Return the document at index `idx` of the block.
-    #[inline(always)]
-    pub fn doc(&self, idx: usize) -> u32 {
-        self.doc_decoder.output(idx)
-    }
-
-    /// Return the array of `term freq` in the block.
-    #[inline]
-    pub fn freqs(&self) -> &[u32] {
-        debug_assert!(self.block_is_loaded());
-        self.freq_decoder.output_array()
-    }
-
-    /// Return the frequency at index `idx` of the block.
-    #[inline]
-    pub fn freq(&self, idx: usize) -> u32 {
-        debug_assert!(self.block_is_loaded());
-        self.freq_decoder.output(idx)
-    }
-
-    /// Returns the length of the current block.
-    ///
-    /// All blocks have a length of `NUM_DOCS_PER_BLOCK`,
-    /// except the last block that may have a length
-    /// of any number between 1 and `NUM_DOCS_PER_BLOCK - 1`
-    #[inline]
-    pub fn block_len(&self) -> usize {
-        debug_assert!(self.block_is_loaded());
-        self.doc_decoder.output_len
-    }
-
-    /// Position on a block that may contains `target_doc`.
-    ///
-    /// If all docs are smaller than target, the block loaded may be empty,
-    /// or be the last an incomplete VInt block.
-    pub fn seek(&mut self, target_doc: DocId) {
-        self.shallow_seek(target_doc);
-        self.load_block();
-    }
-
-    pub(crate) fn position_offset(&self) -> u64 {
-        self.skip_reader.position_offset()
-    }
-
-    /// Dangerous API! This calls seek on the skip list,
-    /// but does not `.load_block()` afterwards.
-    ///
-    /// `.load_block()` needs to be called manually afterwards.
-    /// If all docs are smaller than target, the block loaded may be empty,
-    /// or be the last an incomplete VInt block.
-    pub(crate) fn shallow_seek(&mut self, target_doc: DocId) {
-        if self.skip_reader.seek(target_doc) {
-            self.block_max_score_cache = None;
-        }
-    }
-
-    pub(crate) fn block_is_loaded(&self) -> bool {
-        self.loaded_offset == self.skip_reader.byte_offset()
-    }
-
-    pub(crate) fn load_block(&mut self) {
-        let offset = self.skip_reader.byte_offset();
-        if self.loaded_offset == offset {
-            return;
-        }
-        self.loaded_offset = offset;
-        match self.skip_reader.block_info() {
-            BlockInfo::BitPacked {
-                doc_num_bits,
-                tf_num_bits,
-                ..
-            } => {
-                decode_bitpacked_block(
-                    &mut self.doc_decoder,
-                    if let FreqReadingOption::ReadFreq = self.freq_reading_option {
-                        Some(&mut self.freq_decoder)
-                    } else {
-                        None
-                    },
-                    &self.data.as_slice()[offset..],
-                    self.skip_reader.last_doc_in_previous_block,
-                    doc_num_bits,
-                    tf_num_bits,
-                );
-            }
-            BlockInfo::VInt { num_docs } => {
-                let data = {
-                    if num_docs == 0 {
-                        &[]
-                    } else {
-                        &self.data.as_slice()[offset..]
-                    }
-                };
-                decode_vint_block(
-                    &mut self.doc_decoder,
-                    if let FreqReadingOption::ReadFreq = self.freq_reading_option {
-                        Some(&mut self.freq_decoder)
-                    } else {
-                        None
-                    },
-                    data,
-                    self.skip_reader.last_doc_in_previous_block,
-                    num_docs as usize,
-                );
-            }
-        }
-    }
-
-    /// Advance to the next block.
-    ///
-    /// Returns false iff there was no remaining blocks.
-    pub fn advance(&mut self) {
-        self.skip_reader.advance();
-        self.block_max_score_cache = None;
-        self.load_block();
-    }
-
-    /// Returns an empty segment postings object
-    pub fn empty() -> BlockSegmentPostings {
-        BlockSegmentPostings {
-            doc_decoder: BlockDecoder::with_val(TERMINATED),
-            loaded_offset: 0,
-            freq_decoder: BlockDecoder::with_val(1),
-            freq_reading_option: FreqReadingOption::NoFreq,
-            block_max_score_cache: None,
-            doc_freq: 0,
-            data: OwnedBytes::empty(),
-            skip_reader: SkipReader::new(OwnedBytes::empty(), 0, IndexRecordOption::Basic),
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::BlockSegmentPostings;
-    use crate::common::HasLen;
-    use crate::core::Index;
-    use crate::docset::{DocSet, TERMINATED};
-    use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
-    use crate::postings::postings::Postings;
-    use crate::postings::SegmentPostings;
-    use crate::schema::IndexRecordOption;
-    use crate::schema::Schema;
-    use crate::schema::Term;
-    use crate::schema::INDEXED;
-    use crate::DocId;
-
-    #[test]
-    fn test_empty_segment_postings() {
-        let mut postings = SegmentPostings::empty();
-        assert_eq!(postings.doc(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
-        assert_eq!(postings.doc_freq(), 0);
-        assert_eq!(postings.len(), 0);
-    }
-
-    #[test]
-    fn test_empty_postings_doc_returns_terminated() {
-        let mut postings = SegmentPostings::empty();
-        assert_eq!(postings.doc(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
-    }
-
-    #[test]
-    fn test_empty_postings_doc_term_freq_returns_0() {
-        let postings = SegmentPostings::empty();
-        assert_eq!(postings.term_freq(), 1);
-    }
-
-    #[test]
-    fn test_empty_block_segment_postings() {
-        let mut postings = BlockSegmentPostings::empty();
-        assert!(postings.docs().is_empty());
-        assert_eq!(postings.doc_freq(), 0);
-        postings.advance();
-        assert!(postings.docs().is_empty());
-        assert_eq!(postings.doc_freq(), 0);
-    }
-
-    #[test]
-    fn test_block_segment_postings() {
-        let mut block_segments = build_block_postings(&(0..100_000).collect::<Vec<u32>>());
-        let mut offset: u32 = 0u32;
-        // checking that the `doc_freq` is correct
-        assert_eq!(block_segments.doc_freq(), 100_000);
-        loop {
-            let block = block_segments.docs();
-            if block.is_empty() {
-                break;
-            }
-            for (i, doc) in block.iter().cloned().enumerate() {
-                assert_eq!(offset + (i as u32), doc);
-            }
-            offset += block.len() as u32;
-            block_segments.advance();
-        }
-    }
-
-    #[test]
-    fn test_skip_right_at_new_block() {
-        let mut doc_ids = (0..128).collect::<Vec<u32>>();
-        // 128 is missing
-        doc_ids.push(129);
-        doc_ids.push(130);
-        {
-            let block_segments = build_block_postings(&doc_ids);
-            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
-            assert_eq!(docset.seek(128), 129);
-            assert_eq!(docset.doc(), 129);
-            assert_eq!(docset.advance(), 130);
-            assert_eq!(docset.doc(), 130);
-            assert_eq!(docset.advance(), TERMINATED);
-        }
-        {
-            let block_segments = build_block_postings(&doc_ids);
-            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
-            assert_eq!(docset.seek(129), 129);
-            assert_eq!(docset.doc(), 129);
-            assert_eq!(docset.advance(), 130);
-            assert_eq!(docset.doc(), 130);
-            assert_eq!(docset.advance(), TERMINATED);
-        }
-        {
-            let block_segments = build_block_postings(&doc_ids);
-            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
-            assert_eq!(docset.doc(), 0);
-            assert_eq!(docset.seek(131), TERMINATED);
-            assert_eq!(docset.doc(), TERMINATED);
-        }
-    }
-
-    fn build_block_postings(docs: &[DocId]) -> BlockSegmentPostings {
-        let mut schema_builder = Schema::builder();
-        let int_field = schema_builder.add_u64_field("id", INDEXED);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
-        let mut last_doc = 0u32;
-        for &doc in docs {
-            for _ in last_doc..doc {
-                index_writer.add_document(doc!(int_field=>1u64));
-            }
-            index_writer.add_document(doc!(int_field=>0u64));
-            last_doc = doc + 1;
-        }
-        index_writer.commit().unwrap();
-        let searcher = index.reader().unwrap().searcher();
-        let segment_reader = searcher.segment_reader(0);
-        let inverted_index = segment_reader.inverted_index(int_field).unwrap();
-        let term = Term::from_field_u64(int_field, 0u64);
-        let term_info = inverted_index.get_term_info(&term).unwrap().unwrap();
-        inverted_index
-            .read_block_postings_from_terminfo(&term_info, IndexRecordOption::Basic)
-            .unwrap()
-    }
-
-    #[test]
-    fn test_block_segment_postings_seek() {
-        let mut docs = vec![0];
-        for i in 0..1300 {
-            docs.push((i * i / 100) + i);
-        }
-        let mut block_postings = build_block_postings(&docs[..]);
-        for i in vec![0, 424, 10000] {
-            block_postings.seek(i);
-            let docs = block_postings.docs();
-            assert!(docs[0] <= i);
-            assert!(docs.last().cloned().unwrap_or(0u32) >= i);
-        }
-        block_postings.seek(100_000);
-        assert_eq!(block_postings.doc(COMPRESSION_BLOCK_SIZE - 1), TERMINATED);
-    }
-
-    #[test]
-    fn test_reset_block_segment_postings() -> crate::Result<()> {
-        let mut schema_builder = Schema::builder();
-        let int_field = schema_builder.add_u64_field("id", INDEXED);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
-        // create two postings list, one containg even number,
-        // the other containing odd numbers.
-        for i in 0..6 {
-            let doc = doc!(int_field=> (i % 2) as u64);
-            index_writer.add_document(doc);
-        }
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let segment_reader = searcher.segment_reader(0);
-
-        let mut block_segments;
-        {
-            let term = Term::from_field_u64(int_field, 0u64);
-            let inverted_index = segment_reader.inverted_index(int_field)?;
-            let term_info = inverted_index.get_term_info(&term)?.unwrap();
-            block_segments = inverted_index
-                .read_block_postings_from_terminfo(&term_info, IndexRecordOption::Basic)?;
-        }
-        assert_eq!(block_segments.docs(), &[0, 2, 4]);
-        {
-            let term = Term::from_field_u64(int_field, 1u64);
-            let inverted_index = segment_reader.inverted_index(int_field)?;
-            let term_info = inverted_index.get_term_info(&term)?.unwrap();
-            inverted_index.reset_block_postings_from_terminfo(&term_info, &mut block_segments)?;
-        }
-        assert_eq!(block_segments.docs(), &[1, 3, 5]);
-        Ok(())
-    }
-}

src/postings/compression/mod.rs

@@ -17,12 +17,6 @@ pub struct BlockEncoder {
     pub output_len: usize,
 }
 
-impl Default for BlockEncoder {
-    fn default() -> Self {
-        BlockEncoder::new()
-    }
-}
-
 impl BlockEncoder {
     pub fn new() -> BlockEncoder {
         BlockEncoder {
@@ -52,23 +46,19 @@ impl BlockEncoder {
 /// We ensure that the OutputBuffer is align on 128 bits
 /// in order to run SSE2 linear search on it.
 #[repr(align(128))]
-#[derive(Clone)]
 pub(crate) struct AlignedBuffer(pub [u32; COMPRESSION_BLOCK_SIZE]);
 
-#[derive(Clone)]
 pub struct BlockDecoder {
     bitpacker: BitPacker4x,
     output: AlignedBuffer,
     pub output_len: usize,
 }
 
-impl Default for BlockDecoder {
+impl BlockDecoder {
-    fn default() -> Self {
+    pub fn new() -> BlockDecoder {
         BlockDecoder::with_val(0u32)
     }
-}
 
-impl BlockDecoder {
     pub fn with_val(val: u32) -> BlockDecoder {
         BlockDecoder {
             bitpacker: BitPacker4x::new(),
@@ -100,8 +90,8 @@ impl BlockDecoder {
     }
 
     #[inline]
-    pub(crate) fn output_aligned(&self) -> &AlignedBuffer {
+    pub(crate) fn output_aligned(&self) -> (&AlignedBuffer, usize) {
-        &self.output
+        (&self.output, self.output_len)
     }
 
     #[inline]
@@ -144,14 +134,11 @@ pub trait VIntDecoder {
     /// For instance, if delta encoded are `1, 3, 9`, and the
     /// `offset` is 5, then the output will be:
     /// `5 + 1 = 6, 6 + 3= 9, 9 + 9 = 18`
-    ///
+    fn uncompress_vint_sorted<'a>(
-    /// The value given in `padding` will be used to fill the remaining `128 - num_els` values.
-    fn uncompress_vint_sorted(
         &mut self,
-        compressed_data: &[u8],
+        compressed_data: &'a [u8],
         offset: u32,
         num_els: usize,
-        padding: u32,
     ) -> usize;
 
     /// Uncompress an array of `u32s`, compressed using variable
@@ -159,14 +146,7 @@ pub trait VIntDecoder {
     ///
     /// The method takes a number of int to decompress, and returns
     /// the amount of bytes that were read to decompress them.
-    ///
+    fn uncompress_vint_unsorted<'a>(&mut self, compressed_data: &'a [u8], num_els: usize) -> usize;
-    /// The value given in `padding` will be used to fill the remaining `128 - num_els` values.
-    fn uncompress_vint_unsorted(
-        &mut self,
-        compressed_data: &[u8],
-        num_els: usize,
-        padding: u32,
-    ) -> usize;
 }
 
 impl VIntEncoder for BlockEncoder {
@@ -180,26 +160,18 @@ impl VIntEncoder for BlockEncoder {
 }
 
 impl VIntDecoder for BlockDecoder {
-    fn uncompress_vint_sorted(
+    fn uncompress_vint_sorted<'a>(
         &mut self,
-        compressed_data: &[u8],
+        compressed_data: &'a [u8],
         offset: u32,
         num_els: usize,
-        padding: u32,
     ) -> usize {
         self.output_len = num_els;
-        self.output.0.iter_mut().for_each(|el| *el = padding);
         vint::uncompress_sorted(compressed_data, &mut self.output.0[..num_els], offset)
     }
 
-    fn uncompress_vint_unsorted(
+    fn uncompress_vint_unsorted<'a>(&mut self, compressed_data: &'a [u8], num_els: usize) -> usize {
-        &mut self,
-        compressed_data: &[u8],
-        num_els: usize,
-        padding: u32,
-    ) -> usize {
         self.output_len = num_els;
-        self.output.0.iter_mut().for_each(|el| *el = padding);
         vint::uncompress_unsorted(compressed_data, &mut self.output.0[..num_els])
     }
 }
@@ -208,14 +180,13 @@ impl VIntDecoder for BlockDecoder {
 pub mod tests {
 
     use super::*;
-    use crate::TERMINATED;
 
     #[test]
     fn test_encode_sorted_block() {
         let vals: Vec<u32> = (0u32..128u32).map(|i| i * 7).collect();
         let mut encoder = BlockEncoder::new();
         let (num_bits, compressed_data) = encoder.compress_block_sorted(&vals, 0);
-        let mut decoder = BlockDecoder::default();
+        let mut decoder = BlockDecoder::new();
         {
             let consumed_num_bytes = decoder.uncompress_block_sorted(compressed_data, 0, num_bits);
             assert_eq!(consumed_num_bytes, compressed_data.len());
@@ -228,9 +199,9 @@ pub mod tests {
     #[test]
     fn test_encode_sorted_block_with_offset() {
         let vals: Vec<u32> = (0u32..128u32).map(|i| 11 + i * 7).collect();
-        let mut encoder = BlockEncoder::default();
+        let mut encoder = BlockEncoder::new();
         let (num_bits, compressed_data) = encoder.compress_block_sorted(&vals, 10);
-        let mut decoder = BlockDecoder::default();
+        let mut decoder = BlockDecoder::new();
         {
             let consumed_num_bytes = decoder.uncompress_block_sorted(compressed_data, 10, num_bits);
             assert_eq!(consumed_num_bytes, compressed_data.len());
@@ -245,11 +216,11 @@ pub mod tests {
         let mut compressed: Vec<u8> = Vec::new();
         let n = 128;
         let vals: Vec<u32> = (0..n).map(|i| 11u32 + (i as u32) * 7u32).collect();
-        let mut encoder = BlockEncoder::default();
+        let mut encoder = BlockEncoder::new();
         let (num_bits, compressed_data) = encoder.compress_block_sorted(&vals, 10);
         compressed.extend_from_slice(compressed_data);
         compressed.push(173u8);
-        let mut decoder = BlockDecoder::default();
+        let mut decoder = BlockDecoder::new();
         {
             let consumed_num_bytes = decoder.uncompress_block_sorted(&compressed, 10, num_bits);
             assert_eq!(consumed_num_bytes, compressed.len() - 1);
@@ -265,11 +236,11 @@ pub mod tests {
         let mut compressed: Vec<u8> = Vec::new();
         let n = 128;
         let vals: Vec<u32> = (0..n).map(|i| 11u32 + (i as u32) * 7u32 % 12).collect();
-        let mut encoder = BlockEncoder::default();
+        let mut encoder = BlockEncoder::new();
         let (num_bits, compressed_data) = encoder.compress_block_unsorted(&vals);
         compressed.extend_from_slice(compressed_data);
         compressed.push(173u8);
-        let mut decoder = BlockDecoder::default();
+        let mut decoder = BlockDecoder::new();
         {
             let consumed_num_bytes = decoder.uncompress_block_unsorted(&compressed, num_bits);
             assert_eq!(consumed_num_bytes + 1, compressed.len());
@@ -280,27 +251,20 @@ pub mod tests {
         }
     }
 
-    #[test]
-    fn test_block_decoder_initialization() {
-        let block = BlockDecoder::with_val(TERMINATED);
-        assert_eq!(block.output(0), TERMINATED);
-    }
     #[test]
     fn test_encode_vint() {
-        const PADDING_VALUE: u32 = 234_234_345u32;
+        {
-        let expected_length = 154;
+            let expected_length = 154;
-        let mut encoder = BlockEncoder::new();
+            let mut encoder = BlockEncoder::new();
-        let input: Vec<u32> = (0u32..123u32).map(|i| 4 + i * 7 / 2).into_iter().collect();
+            let input: Vec<u32> = (0u32..123u32).map(|i| 4 + i * 7 / 2).into_iter().collect();
-        for offset in &[0u32, 1u32, 2u32] {
+            for offset in &[0u32, 1u32, 2u32] {
-            let encoded_data = encoder.compress_vint_sorted(&input, *offset);
+                let encoded_data = encoder.compress_vint_sorted(&input, *offset);
-            assert!(encoded_data.len() <= expected_length);
+                assert!(encoded_data.len() <= expected_length);
-            let mut decoder = BlockDecoder::default();
+                let mut decoder = BlockDecoder::new();
-            let consumed_num_bytes =
+                let consumed_num_bytes =
-                decoder.uncompress_vint_sorted(&encoded_data, *offset, input.len(), PADDING_VALUE);
+                    decoder.uncompress_vint_sorted(&encoded_data, *offset, input.len());
-            assert_eq!(consumed_num_bytes, encoded_data.len());
+                assert_eq!(consumed_num_bytes, encoded_data.len());
-            assert_eq!(input, decoder.output_array());
+                assert_eq!(input, decoder.output_array());
-            for i in input.len()..COMPRESSION_BLOCK_SIZE {
-                assert_eq!(decoder.output(i), PADDING_VALUE);
             }
         }
     }
@@ -310,7 +274,6 @@ pub mod tests {
 mod bench {
 
     use super::*;
-    use crate::TERMINATED;
     use rand::rngs::StdRng;
     use rand::Rng;
     use rand::SeedableRng;
@@ -341,7 +304,7 @@ mod bench {
         let mut encoder = BlockEncoder::new();
         let data = generate_array(COMPRESSION_BLOCK_SIZE, 0.1);
         let (num_bits, compressed) = encoder.compress_block_sorted(&data, 0u32);
-        let mut decoder = BlockDecoder::default();
+        let mut decoder = BlockDecoder::new();
         b.iter(|| {
             decoder.uncompress_block_sorted(compressed, 0u32, num_bits);
         });
@@ -376,9 +339,9 @@ mod bench {
         let mut encoder = BlockEncoder::new();
         let data = generate_array(NUM_INTS_BENCH_VINT, 0.001);
         let compressed = encoder.compress_vint_sorted(&data, 0u32);
-        let mut decoder = BlockDecoder::default();
+        let mut decoder = BlockDecoder::new();
         b.iter(|| {
-            decoder.uncompress_vint_sorted(compressed, 0u32, NUM_INTS_BENCH_VINT, TERMINATED);
+            decoder.uncompress_vint_sorted(compressed, 0u32, NUM_INTS_BENCH_VINT);
         });
     }
 }