Added coveralls

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: Tantivy CI
+
+on: [push]
+
+jobs:
+  test:
+    name: Test Suite
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
+      - uses: actions-rs/cargo@v1
+        with:
+          command: test
+      - uses: actions-rs/cargo@v1
+        with:
+          command: fmt
+          args: --all -- --check
+      - run: rustup component add clippy
+      - uses: actions-rs/cargo@v1
+        with:
+          command: clippy
+          args: -- -D warnings
+

.github/workflows/coveralls.yml

@@ -0,0 +1,66 @@
+on: [push]
+
+name: Code coverage with grcov
+
+jobs:
+  grcov:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os:
+          - ubuntu-latest
+            #- macOS-latest
+            #- windows-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          override: true
+          profile: minimal
+
+      - name: Execute tests
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --all --lib
+        env:
+          CARGO_INCREMENTAL: 0
+          RUSTFLAGS: "-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off -Cpanic=abort -Zpanic_abort_tests"
+
+      # Note that `actions-rs/grcov` Action can install `grcov` too,
+      # but can't use faster installation methods yet.
+      # As a temporary experiment `actions-rs/install` Action plugged in here.
+      # Consider **NOT** to copy that into your workflow,
+      # but use `actions-rs/grcov` only
+      - name: Pre-installing grcov
+        uses: actions-rs/install@v0.1
+        with:
+          crate: grcov
+          use-tool-cache: true
+
+      - name: Gather coverage data
+        id: coverage
+        uses: actions-rs/grcov@v0.1
+        with:
+          coveralls-token: ${{ secrets.COVERALLS_TOKEN }}
+
+      - name: Coveralls upload
+        uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          parallel: true
+          path-to-lcov: ${{ steps.coverage.outputs.report }}
+
+  grcov_finalize:
+    runs-on: ubuntu-latest
+    needs: grcov
+    steps:
+      - name: Coveralls finalization
+        uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          parallel-finished: true

.gitignore

@@ -12,4 +12,3 @@ cpp/simdcomp/bitpackingbenchmark
 *.bk
 .idea
 trace.dat
-cargo-timing*

CHANGELOG.md

@@ -1,29 +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

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy"
-version = "0.14.0-dev"
+version = "0.13.0"
 authors = ["Paul Masurel <paul.masurel@gmail.com>"]
 license = "MIT"
 categories = ["database-implementations", "data-structures"]
@@ -13,51 +13,52 @@ keywords = ["search", "information", "retrieval"]
 edition = "2018"
 
 [dependencies]
-base64 = "0.13"
-byteorder = "1"
-crc32fast = "1"
-once_cell = "1"
-regex ={version = "1", default-features = false, features = ["std"]}
+base64 = "0.12.0"
+byteorder = "1.0"
+crc32fast = "1.2.0"
+once_cell = "1.0"
+regex ={version = "1.3.0", default-features = false, features = ["std"]}
 tantivy-fst = "0.3"
 memmap = {version = "0.7", optional=true}
-lz4 = {version="1", optional=true}
-brotli = {version="3.3.0", optional=true}
+lz4 = {version="1.20", 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_json = "1"
-num_cpus = "1"
+serde = {version="1.0", features=["derive"]}
+serde_json = "1.0"
+num_cpus = "1.2"
 fs2={version="0.4", optional=true}
 levenshtein_automata = "0.2"
+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" }
-stable_deref_trait = "1"
-rust-stemmers = "1"
-downcast-rs = "1"
+owning_ref = "0.4"
+stable_deref_trait = "1.0.0"
+rust-stemmers = "1.2"
+downcast-rs = { version="1.0" }
+tantivy-query-grammar = { version="0.13", path="./query-grammar" }
 bitpacking = {version="0.8", default-features = false, features=["bitpacker4x"]}
 census = "0.4"
-fnv = "1"
-thiserror = "1.0"
-htmlescape = "0.3"
+fnv = "1.0.6"
+owned-read = "0.4"
+failure = "0.1"
+htmlescape = "0.3.1"
 fail = "0.4"
 murmurhash32 = "0.2"
 chrono = "0.4"
-smallvec = "1"
+smallvec = "1.0"
 rayon = "1"
-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"
@@ -74,12 +75,12 @@ overflow-checks = true
 
 [features]
 default = ["mmap"]
-mmap = ["fs2", "tempfile", "memmap"]
-brotli-compression = ["brotli"]
+mmap = ["atomicwrites", "fs2", "memmap", "notify"]
 lz4-compression = ["lz4"]
 failpoints = ["fail/failpoints"]
 unstable = [] # useful for benches.
 wasm-bindgen = ["uuid/wasm-bindgen"]
+scoref64 = [] # scores are f64 instead of f32. was introduced to debug blockwand.
 
 [workspace]
 members = ["query-grammar"]
@@ -98,7 +99,3 @@ 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)
 
@@ -33,6 +34,11 @@ Tantivy is, in fact, strongly inspired by Lucene's design.
 The following [benchmark](https://tantivy-search.github.io/bench/) break downs 
 performance for different type of queries / collection.
 
+
+In general, Tantivy tends to be 
+- slower than Lucene on union with a Top-K due to Block-WAND optimization.
+- faster than Lucene on intersection and phrase queries. 
+
 Your mileage WILL vary depending on the nature of queries and their load.
 
 # Features
@@ -84,7 +90,7 @@ 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
 

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);
-            for token in token_stream {
-                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/faceted_search_with_tweaked_score.rs

@@ -56,12 +56,12 @@ fn main() -> tantivy::Result<()> {
         );
         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 mut 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())
+                    .filter_map(|key| facet_dict.term_ord(key.encoded_str()))
                     .collect();
 
                 let mut facet_ords_buffer: Vec<u64> = Vec::with_capacity(20);

examples/iterating_docs_and_positions.rs

@@ -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
@@ -58,7 +58,7 @@ 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);
@@ -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
@@ -115,7 +115,7 @@ 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 {
                 let docs = block_segment_postings.docs();

examples/pre_tokenized_text.rs

@@ -17,7 +17,12 @@ use tantivy::{doc, Index, ReloadPolicy};
 use tempfile::TempDir;
 
 fn pre_tokenize_text(text: &str) -> Vec<Token> {
-    SimpleTokenizer.token_stream(text).collect()
+    let mut token_stream = SimpleTokenizer.token_stream(text);
+    let mut tokens = vec![];
+    while token_stream.advance() {
+        tokens.push(token_stream.token().clone());
+    }
+    tokens
 }
 
 fn main() -> tantivy::Result<()> {

examples/snippet.rs

@@ -51,7 +51,7 @@ fn main() -> tantivy::Result<()> {
 
     let top_docs = searcher.search(&query, &TopDocs::with_limit(10))?;
 
-    let mut snippet_generator = SnippetGenerator::create(&searcher, &*query, body)?;
+    let snippet_generator = SnippetGenerator::create(&searcher, &*query, body)?;
 
     for (score, doc_address) in top_docs {
         let doc = searcher.doc(doc_address)?;

examples/stop_words.rs

@@ -50,13 +50,12 @@ fn main() -> tantivy::Result<()> {
 
     // This tokenizer lowers all of the text (to help with stop word matching)
     // then removes all instances of `the` and `and` from the corpus
-    let tokenizer = analyzer_builder(SimpleTokenizer)
-        .filter(LowerCaser::new())
+    let tokenizer = TextAnalyzer::from(SimpleTokenizer)
+        .filter(LowerCaser)
         .filter(StopWordFilter::remove(vec![
             "the".to_string(),
             "and".to_string(),
-        ]))
-        .build();
+        ]));
 
     index.tokenizers().register("stoppy", tokenizer);
 

query-grammar/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy-query-grammar"
-version = "0.14.0-dev"
+version = "0.13.0"
 authors = ["Paul Masurel <paul.masurel@gmail.com>"]
 license = "MIT"
 categories = ["database-implementations", "data-structures"]

query-grammar/src/occur.rs

@@ -52,7 +52,7 @@ mod test {
     use crate::Occur;
 
     #[test]
-    fn test_occur_compose() {
+    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!(

query-grammar/src/query_grammar.rs

@@ -9,10 +9,8 @@ use combine::{
 
 fn field<'a>() -> impl Parser<&'a str, Output = String> {
     (
-        (letter().or(char('_'))),
-        many(satisfy(|c: char| {
-            c.is_alphanumeric() || c == '_' || c == '-'
-        })),
+        letter(),
+        many(satisfy(|c: char| c.is_alphanumeric() || c == '_')),
     )
         .skip(char(':'))
         .map(|(s1, s2): (char, String)| format!("{}{}", s1, s2))
@@ -281,8 +279,6 @@ 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;
 
@@ -300,10 +296,9 @@ 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(())
+    fn test_occur_symbol() {
+        assert_eq!(super::occur_symbol().parse("-"), Ok((Occur::MustNot, "")));
+        assert_eq!(super::occur_symbol().parse("+"), Ok((Occur::Must, "")));
     }
 
     #[test]
@@ -415,25 +410,6 @@ mod test {
         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

src/collector/custom_score_top_collector.rs

@@ -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,

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

@@ -7,6 +7,7 @@ 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;
@@ -265,7 +266,10 @@ 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();
@@ -274,7 +278,7 @@ 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
@@ -368,12 +372,9 @@ impl SegmentCollector for FacetSegmentCollector {
             }
             let mut facet = vec![];
             let facet_ord = self.collapse_facet_ords[collapsed_facet_ord];
-            // TODO handle errors.
-            if facet_dict.ord_to_term(facet_ord as u64, &mut facet).is_ok() {
-                if let Ok(facet) = Facet::from_encoded(facet) {
-                    facet_counts.insert(facet, count);
-                }
-            }
+            facet_dict.ord_to_term(facet_ord as u64, &mut facet);
+            // TODO
+            facet_counts.insert(Facet::from_encoded(facet).unwrap(), count);
         }
         FacetCounts { facet_counts }
     }
@@ -471,7 +472,7 @@ 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 +531,7 @@ 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 +550,12 @@ 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 +568,8 @@ mod tests {
         index_writer.add_document(doc!(
             facet_field => Facet::from_text(&"/D/C/A"),
         ));
-        index_writer.commit()?;
-        let reader = index.reader()?;
+        index_writer.commit().unwrap();
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         assert_eq!(searcher.num_docs(), 4);
 
@@ -585,17 +586,17 @@ 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")?;
-            assert_eq!(1, searcher.search(&query, &Count).unwrap());
+            let query_parser = QueryParser::for_index(&index, vec![]);
+            {
+                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 +631,7 @@ 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 +684,7 @@ 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

@@ -111,12 +111,6 @@ 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.
 pub trait Fruit: Send + downcast_rs::Downcast {}
@@ -139,13 +133,13 @@ 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.
@@ -160,10 +154,7 @@ pub trait Collector: Sync + Send {
 
     /// Combines the fruit associated to the collection of each segments
     /// into one fruit.
-    fn merge_fruits(
-        &self,
-        segment_fruits: Vec<<Self::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<Self::Fruit>;
+    fn merge_fruits(&self, segment_fruits: Vec<Self::Fruit>) -> crate::Result<Self::Fruit>;
 
     /// Created a segment collector and
     fn collect_segment(
@@ -233,11 +224,11 @@ 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 +282,7 @@ where
         self.0.requires_scoring() || self.1.requires_scoring() || self.2.requires_scoring()
     }
 
-    fn merge_fruits(
-        &self,
-        children: Vec<<Self::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<Self::Fruit> {
+    fn merge_fruits(&self, children: Vec<Self::Fruit>) -> crate::Result<Self::Fruit> {
         let mut one_fruits = vec![];
         let mut two_fruits = vec![];
         let mut three_fruits = vec![];
@@ -361,10 +349,7 @@ where
             || self.3.requires_scoring()
     }
 
-    fn merge_fruits(
-        &self,
-        children: Vec<<Self::Child as SegmentCollector>::Fruit>,
-    ) -> crate::Result<Self::Fruit> {
+    fn merge_fruits(&self, children: Vec<Self::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())
@@ -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."),
         })
     }
 

src/collector/top_score_collector.rs

@@ -1,4 +1,6 @@
 use super::Collector;
+use crate::collector::custom_score_top_collector::CustomScoreTopCollector;
+use crate::collector::top_collector::TopSegmentCollector;
 use crate::collector::top_collector::{ComparableDoc, TopCollector};
 use crate::collector::tweak_score_top_collector::TweakedScoreTopCollector;
 use crate::collector::{
@@ -12,71 +14,8 @@ 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::collections::BinaryHeap;
 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 +38,7 @@ 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"));
@@ -134,7 +73,7 @@ struct ScorerByFastFieldReader {
 
 impl CustomSegmentScorer<u64> for ScorerByFastFieldReader {
     fn score(&mut self, doc: DocId) -> u64 {
-        self.ff_reader.get(doc)
+        self.ff_reader.get_u64(u64::from(doc))
     }
 }
 
@@ -148,10 +87,10 @@ 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
                 ))
             })?;
@@ -173,8 +112,6 @@ impl TopDocs {
     /// 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;
@@ -186,7 +123,7 @@ 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).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"));
@@ -211,14 +148,6 @@ impl TopDocs {
 
     /// 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 +163,13 @@ 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 +177,25 @@ 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.
-    ///     let top_books_by_rating = TopDocs
+    ///     // Note the generics parameter that needs to match the
+    ///     // 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 +205,21 @@ 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
-    ///  
-    /// To confortably work with `u64`s, `i64`s, `f64`s, or `date`s, please refer to
-    /// [.order_by_fast_field(...)](#method.order_by_fast_field) method.
+    /// # Panics
+    ///
+    /// May panic if the field requested is not a fast field.
+    ///
     pub fn order_by_u64_field(
         self,
         field: Field,
     ) -> impl Collector<Fruit = Vec<(u64, DocAddress)>> {
-        CustomScoreTopCollector::new(ScorerByField { field }, self.0.into_tscore())
-    }
-
-    /// 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,
-        }
+        self.custom_score(ScorerByField { field })
     }
 
     /// Ranks the documents using a custom score.
@@ -414,7 +264,7 @@ 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));
@@ -474,7 +324,7 @@ 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())
     }
@@ -521,7 +371,7 @@ 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();
@@ -588,7 +438,7 @@ 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())
     }
@@ -711,7 +561,7 @@ 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"));
@@ -728,7 +578,7 @@ mod tests {
     }
 
     #[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]);
@@ -872,94 +722,6 @@ 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() {
@@ -982,41 +744,29 @@ 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 mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(size=>1u64));
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
+        let (index, _) = index("beer", title, schema, |index_writer| {
+            index_writer.add_document(doc!(
+                title => "bottle of beer",
+                size => 12u64,
+            ));
+        });
+        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();
-        assert!(
-            matches!(err, crate::TantivyError::SchemaError(msg) if msg == "Field requested (Field(0)) is not a fast field.")
-        );
-        Ok(())
-    }
-
-    #[test]
-    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(())
+        let err = top_collector.for_segment(0, segment);
+        if let Err(crate::TantivyError::SchemaError(msg)) = err {
+            assert_eq!(
+                msg,
+                "Field requested (Field(1)) is not a i64/u64 fast field."
+            );
+        } else {
+            assert!(false);
+        }
     }
 
     #[test]
@@ -1070,7 +820,8 @@ 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

@@ -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)>;

src/common/bitpacker.rs

@@ -1,7 +1,6 @@
 use byteorder::{ByteOrder, LittleEndian, WriteBytesExt};
 use std::io;
-
-use crate::directory::OwnedBytes;
+use std::ops::Deref;
 
 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 {
-    pub fn new(data: OwnedBytes, num_bits: u8) -> BitUnpacker {
+impl<Data> BitUnpacker<Data>
+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/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 super::HasLen;
+use std::io::Write;
+use std::io::{self, Read};
 
 #[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`.
-    pub fn open(data: &FileSlice) -> io::Result<CompositeFile> {
+    /// `ReadOnlySource`.
+    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
-            .slice(footer_start, footer_start + footer_len)
-            .read_bytes()?;
+        let footer_data = data.slice(footer_start, footer_start + footer_len);
         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))
@@ -194,44 +192,46 @@ mod test {
     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::create();
         {
             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)?;
-            write_0.flush()?;
-            let mut write_4 = composite_write.for_field(Field::from_field_id(4u32));
-            VInt(2).serialize(&mut write_4)?;
-            write_4.flush()?;
-            composite_write.close()?;
+            {
+                let mut write_0 = composite_write.for_field(Field::from_field_id(0u32));
+                VInt(32431123u64).serialize(&mut write_0).unwrap();
+                write_0.flush().unwrap();
+            }
+
+            {
+                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 composite_file = CompositeFile::open(&r)?;
+            let r = directory.open_read(path).unwrap();
+            let composite_file = CompositeFile::open(&r).unwrap();
             {
                 let file0 = composite_file
                     .open_read(Field::from_field_id(0u32))
-                    .unwrap()
-                    .read_bytes()?;
+                    .unwrap();
                 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()
-                    .read_bytes()?;
+                    .unwrap();
                 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.
-    /// Note that this method does not trigger any flushing.
-    pub fn finish(self) -> W {
-        self.underlying
+    pub fn finish(mut self) -> io::Result<(W, u64)> {
+        self.flush()?;
+        Ok((self.underlying, self.written_bytes))
     }
 }
 
@@ -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 buffer_restituted: Vec<u8> = counting_writer.finish();
+        let (w, len): (Vec<u8>, u64) = counting_writer.finish().unwrap();
         assert_eq!(len, 10u64);
-        assert_eq!(buffer_restituted.len(), 10);
+        assert_eq!(w.len(), 10);
     }
 }

src/common/mod.rs

@@ -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/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;
@@ -20,8 +19,9 @@ use crate::reader::IndexReaderBuilder;
 use crate::schema::Field;
 use crate::schema::FieldType;
 use crate::schema::Schema;
-use crate::tokenizer::{TextAnalyzerT, TokenizerManager};
+use crate::tokenizer::{TextAnalyzer, TokenizerManager};
 use crate::IndexWriter;
+use std::borrow::BorrowMut;
 use std::collections::HashSet;
 use std::fmt;
 
@@ -57,10 +57,8 @@ pub struct Index {
 }
 
 impl Index {
-    /// Examines the directory to see if it contains an index.
-    ///
-    /// Effectively, it only checks for the presence of the `meta.json` file.
-    pub fn exists<Dir: Directory>(dir: &Dir) -> Result<bool, OpenReadError> {
+    /// Examines the director to see if it contains an index
+    pub fn exists<Dir: Directory>(dir: &Dir) -> bool {
         dir.exists(&META_FILEPATH)
     }
 
@@ -107,7 +105,7 @@ 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)
@@ -115,16 +113,17 @@ 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)?;
-        if index.schema() != schema {
-            return Err(TantivyError::SchemaError(
+        if index.schema() == schema {
+            Ok(index)
+        } else {
+            Err(TantivyError::SchemaError(
                 "An index exists but the schema does not match.".to_string(),
-            ));
+            ))
         }
-        Ok(index)
     }
 
     /// Creates a new index in a temp directory.
@@ -141,9 +140,7 @@ impl Index {
         Index::create(mmap_directory, schema)
     }
 
-    /// Creates a new index given an implementation of the trait `Directory`.
-    ///
-    /// If a directory previously existed, it will be erased.
+    /// Creates a new index given an implementation of the trait `Directory`
     pub fn create<Dir: Directory>(dir: Dir, schema: Schema) -> crate::Result<Index> {
         let directory = ManagedDirectory::wrap(dir)?;
         Index::from_directory(directory, schema)
@@ -152,8 +149,8 @@ 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> {
-        save_new_metas(schema.clone(), &directory)?;
+    fn from_directory(mut directory: ManagedDirectory, schema: Schema) -> crate::Result<Index> {
+        save_new_metas(schema.clone(), directory.borrow_mut())?;
         let metas = IndexMeta::with_schema(schema);
         Index::create_from_metas(directory, &metas, SegmentMetaInventory::default())
     }
@@ -180,11 +177,11 @@ impl Index {
     }
 
     /// Helper to access the tokenizer associated to a specific field.
-    pub fn tokenizer_for_field(&self, field: Field) -> crate::Result<Box<dyn TextAnalyzerT>> {
+    pub fn tokenizer_for_field(&self, field: Field) -> crate::Result<TextAnalyzer> {
         let field_entry = self.schema.get_field_entry(field);
         let field_type = field_entry.field_type();
         let tokenizer_manager: &TokenizerManager = self.tokenizers();
-        let tokenizer_name_opt: Option<Box<dyn TextAnalyzerT>> = match field_type {
+        let tokenizer_name_opt: Option<TextAnalyzer> = match field_type {
             FieldType::Str(text_options) => text_options
                 .get_indexing_options()
                 .map(|text_indexing_options| text_indexing_options.tokenizer().to_string())
@@ -303,15 +300,6 @@ impl Index {
         )
     }
 
-    /// 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.
@@ -399,7 +387,7 @@ 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;
@@ -423,24 +411,24 @@ 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());
     }
 
@@ -448,7 +436,7 @@ 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());
     }
 
@@ -456,7 +444,7 @@ 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!(
@@ -510,28 +498,28 @@ mod tests {
         }
 
         #[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 writer = index.writer_for_tests()?;
-            writer.commit()?;
+            let mut index = Index::create_from_tempdir(schema).unwrap();
+            let mut writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            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]
@@ -551,35 +539,23 @@ mod tests {
             test_index_on_commit_reload_policy_aux(field, &write_index, &reader);
         }
     }
+
     fn test_index_on_commit_reload_policy_aux(field: Field, index: &Index, reader: &IndexReader) {
         let mut reader_index = reader.index();
         let (sender, receiver) = crossbeam::channel::unbounded();
-        let _watch_handle = reader_index
-            .directory_mut()
-            .watch(WatchCallback::new(move || {
-                let _ = sender.send(());
-            }));
-        let mut writer = index.writer_for_tests().unwrap();
+        let _watch_handle = reader_index.directory_mut().watch(Box::new(move || {
+            let _ = sender.send(());
+        }));
+        let mut writer = index.writer_with_num_threads(1, 3_000_000).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
-        // one modify event. It was observed on CI on MacOS.
-        loop {
-            assert!(receiver.recv().is_ok());
-            if reader.searcher().num_docs() == 1 {
-                break;
-            }
-        }
+        assert!(receiver.recv().is_ok());
+        assert_eq!(reader.searcher().num_docs(), 1);
         writer.add_document(doc!(field=>2u64));
         writer.commit().unwrap();
-        // ... Same as above
-        loop {
-            assert!(receiver.recv().is_ok());
-            if reader.searcher().num_docs() == 2 {
-                break;
-            }
-        }
+        assert!(receiver.recv().is_ok());
+        assert_eq!(reader.searcher().num_docs(), 2);
     }
 
     // This test will not pass on windows, because windows
@@ -597,7 +573,7 @@ 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/inverted_index_reader.rs

@@ -1,10 +1,9 @@
-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;
@@ -16,7 +15,7 @@ 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 +23,9 @@ use crate::termdict::TermDictionary;
 /// the `SegmentReader`'s [`.inverted_index(...)`] method
 pub struct InvertedIndexReader {
     termdict: TermDictionary,
-    postings_file_slice: FileSlice,
-    positions_file_slice: FileSlice,
-    positions_idx_file_slice: FileSlice,
+    postings_source: ReadOnlySource,
+    positions_source: ReadOnlySource,
+    positions_idx_source: ReadOnlySource,
     record_option: IndexRecordOption,
     total_num_tokens: u64,
 }
@@ -35,38 +34,42 @@ 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,
-        positions_file_slice: FileSlice,
-        positions_idx_file_slice: FileSlice,
+        postings_source: ReadOnlySource,
+        positions_source: ReadOnlySource,
+        positions_idx_source: ReadOnlySource,
         record_option: IndexRecordOption,
-    ) -> io::Result<InvertedIndexReader> {
-        let (total_num_tokens_slice, postings_body) = postings_file_slice.split(8);
-        let total_num_tokens = u64::deserialize(&mut total_num_tokens_slice.read_bytes()?)?;
-        Ok(InvertedIndexReader {
+    ) -> InvertedIndexReader {
+        let total_num_tokens_data = postings_source.slice(0, 8);
+        let mut total_num_tokens_cursor = total_num_tokens_data.as_slice();
+        let total_num_tokens = u64::deserialize(&mut total_num_tokens_cursor).unwrap_or(0u64);
+        InvertedIndexReader {
             termdict,
-            postings_file_slice: postings_body,
-            positions_file_slice,
-            positions_idx_file_slice,
+            postings_source: postings_source.slice_from(8),
+            positions_source,
+            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(),
-            positions_file_slice: FileSlice::empty(),
-            positions_idx_file_slice: FileSlice::empty(),
+            postings_source: ReadOnlySource::empty(),
+            positions_source: ReadOnlySource::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 +92,11 @@ impl InvertedIndexReader {
         &self,
         term_info: &TermInfo,
         block_postings: &mut BlockSegmentPostings,
-    ) -> io::Result<()> {
-        let start_offset = term_info.postings_start_offset as usize;
-        let stop_offset = term_info.postings_stop_offset as usize;
-        let postings_slice = self.postings_file_slice.slice(start_offset, stop_offset);
-        block_postings.reset(term_info.doc_freq, postings_slice.read_bytes()?);
-        Ok(())
+    ) {
+        let offset = term_info.postings_offset as usize;
+        let end_source = self.postings_source.len();
+        let postings_slice = self.postings_source.slice(offset, end_source);
+        block_postings.reset(term_info.doc_freq, postings_slice);
     }
 
     /// Returns a block postings given a `Term`.
@@ -105,10 +107,9 @@ impl InvertedIndexReader {
         &self,
         term: &Term,
         option: IndexRecordOption,
-    ) -> io::Result<Option<BlockSegmentPostings>> {
-        self.get_term_info(term)?
+    ) -> Option<BlockSegmentPostings> {
+        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`.
@@ -119,12 +120,10 @@ impl InvertedIndexReader {
         &self,
         term_info: &TermInfo,
         requested_option: IndexRecordOption,
-    ) -> io::Result<BlockSegmentPostings> {
-        let postings_data = self.postings_file_slice.slice(
-            term_info.postings_start_offset as usize,
-            term_info.postings_stop_offset as usize,
-        );
-        BlockSegmentPostings::open(
+    ) -> BlockSegmentPostings {
+        let offset = term_info.postings_offset as usize;
+        let postings_data = self.postings_source.slice_from(offset);
+        BlockSegmentPostings::from_data(
             term_info.doc_freq,
             postings_data,
             self.record_option,
@@ -140,23 +139,20 @@ impl InvertedIndexReader {
         &self,
         term_info: &TermInfo,
         option: IndexRecordOption,
-    ) -> io::Result<SegmentPostings> {
-        let block_postings = self.read_block_postings_from_terminfo(term_info, option)?;
+    ) -> SegmentPostings {
+        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 skip_reader = self.positions_idx_file_slice.clone();
+                let position_reader = self.positions_source.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(
-            block_postings,
-            position_stream,
-        ))
+        SegmentPostings::from_block_postings(block_postings, position_stream)
     }
 
     /// Returns the total number of tokens recorded for all documents
@@ -175,31 +171,24 @@ 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(
-        &self,
-        term: &Term,
-        option: IndexRecordOption,
-    ) -> io::Result<Option<SegmentPostings>> {
-        self.get_term_info(term)?
+    pub fn read_postings(&self, term: &Term, option: IndexRecordOption) -> 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>> {
-        self.get_term_info(term)?
+    ) -> Option<SegmentPostings> {
+        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> {
-        Ok(self
-            .get_term_info(term)?
+    pub fn doc_freq(&self, term: &Term) -> u32 {
+        self.get_term_info(term)
             .map(|term_info| term_info.doc_freq)
-            .unwrap_or(0u32))
+            .unwrap_or(0u32)
     }
 }

src/core/searcher.rs

@@ -1,17 +1,18 @@
 use crate::collector::Collector;
 use crate::core::Executor;
-
+use crate::core::InvertedIndexReader;
 use crate::core::SegmentReader;
 use crate::query::Query;
 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, io};
+use std::fmt;
+use std::sync::Arc;
 
 /// Holds a list of `SegmentReader`s ready for search.
 ///
@@ -31,17 +32,17 @@ impl Searcher {
         schema: Schema,
         index: Index,
         segment_readers: Vec<SegmentReader>,
-    ) -> io::Result<Searcher> {
-        let store_readers: Vec<StoreReader> = segment_readers
+    ) -> Searcher {
+        let store_readers = segment_readers
             .iter()
             .map(SegmentReader::get_store_reader)
-            .collect::<io::Result<Vec<_>>>()?;
-        Ok(Searcher {
+            .collect();
+        Searcher {
             schema,
             index,
             segment_readers,
             store_readers,
-        })
+        }
     }
 
     /// Returns the `Index` associated to the `Searcher`
@@ -74,14 +75,13 @@ impl Searcher {
 
     /// Return the overall number of documents containing
     /// the given term.
-    pub fn doc_freq(&self, term: &Term) -> crate::Result<u64> {
-        let mut total_doc_freq = 0;
-        for segment_reader in &self.segment_readers {
-            let inverted_index = segment_reader.inverted_index(term.field())?;
-            let doc_freq = inverted_index.doc_freq(term)?;
-            total_doc_freq += u64::from(doc_freq);
-        }
-        Ok(total_doc_freq)
+    pub fn doc_freq(&self, term: &Term) -> u64 {
+        self.segment_readers
+            .iter()
+            .map(|segment_reader| {
+                u64::from(segment_reader.inverted_index(term.field()).doc_freq(term))
+            })
+            .sum::<u64>()
     }
 
     /// Return the list of segment readers
@@ -147,13 +147,44 @@ impl Searcher {
         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 {
-            space_usage.add_segment(segment_reader.space_usage()?);
+        for segment_reader in self.segment_readers.iter() {
+            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

@@ -4,7 +4,7 @@ use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::directory::error::{OpenReadError, OpenWriteError};
 use crate::directory::Directory;
-use crate::directory::{FileSlice, WritePtr};
+use crate::directory::{ReadOnlySource, WritePtr};
 use crate::indexer::segment_serializer::SegmentSerializer;
 use crate::schema::Schema;
 use crate::Opstamp;
@@ -78,9 +78,10 @@ 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.index.directory().open_read(&path)?;
+        Ok(source)
     }
 
     /// Open one of the component file for *regular* write.

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::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`
 ///
@@ -50,7 +50,7 @@ pub struct SegmentReader {
     fast_fields_readers: Arc<FastFieldReaders>,
     fieldnorm_readers: FieldNormReaders,
 
-    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!(
-                "Field {:?} is not a facet field.",
-                field_entry.name()
-            )));
+            return None;
         }
-        let term_ords_reader = self.fast_fields().u64s(field).ok_or_else(|| {
-            DataCorruption::comment_only(format!(
-                "Cannot find data for hierarchical facet {:?}",
-                field_entry.name()
-            ))
-        })?;
-        let termdict = self
-            .termdict_composite
-            .open_read(field)
-            .map(TermDictionary::open)
-            .unwrap_or_else(|| Ok(TermDictionary::empty()))?;
-        Ok(FacetReader::new(term_ords_reader, termdict))
+        let term_ords_reader = self.fast_fields().u64s(field)?;
+        let termdict_source = self.termdict_composite.open_read(field)?;
+        let termdict = TermDictionary::from_source(&termdict_source);
+        let facet_reader = FacetReader::new(term_ords_reader, termdict);
+        Some(facet_reader)
     }
 
     /// 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> {
-        self.fieldnorm_readers.get_field(field)?.ok_or_else(|| {
+    pub fn get_fieldnorms_reader(&self, field: Field) -> FieldNormReader {
+        if let Some(fieldnorm_reader) = self.fieldnorm_readers.get_field(field) {
+            fieldnorm_reader
+        } 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> {
-        StoreReader::open(self.store_file.clone())
+    pub fn get_store_reader(&self) -> StoreReader {
+        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_composite = CompositeFile::open(&termdict_file)?;
+        let termdict_source = segment.open_read(SegmentComponent::TERMS)?;
+        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_composite = CompositeFile::open(&postings_file)?;
+        let postings_source = segment.open_read(SegmentComponent::POSTINGS)?;
+        let postings_composite = CompositeFile::open(&postings_source)?;
 
         let positions_composite = {
-            if let Ok(positions_file) = segment.open_read(SegmentComponent::POSITIONS) {
-                CompositeFile::open(&positions_file)?
+            if let Ok(source) = segment.open_read(SegmentComponent::POSITIONS) {
+                CompositeFile::open(&source)?
             } else {
                 CompositeFile::empty()
             }
         };
 
         let positions_idx_composite = {
-            if let Ok(positions_skip_file) = segment.open_read(SegmentComponent::POSITIONSSKIP) {
-                CompositeFile::open(&positions_skip_file)?
+            if let Ok(source) = segment.open_read(SegmentComponent::POSITIONSSKIP) {
+                CompositeFile::open(&source)?
             } else {
                 CompositeFile::empty()
             }
@@ -191,14 +183,13 @@ impl SegmentReader {
 
         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(delete_bitset)
+            Some(DeleteBitSet::open(delete_data))
         } 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,
@@ -206,7 +197,7 @@ impl SegmentReader {
             fast_fields_readers: fast_field_readers,
             fieldnorm_readers,
             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.
-    ///
-    /// 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>> {
+    pub fn inverted_index(&self, field: Field) -> 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 Ok(Arc::new(InvertedIndexReader::empty(record_option)));
+            return Arc::new(InvertedIndexReader::empty(field_type));
         }
 
-        let record_option = record_option_opt.unwrap();
-        let postings_file = postings_file_opt.unwrap();
+        let postings_source = postings_source_opt.unwrap();
 
-        let termdict_file: FileSlice = self.termdict_composite.open_read(field)
-            .ok_or_else(||
-               DataCorruption::comment_only(format!("Failed to open field {:?}'s term dictionary in the composite file. Has the schema been modified?", field_entry.name()))
-            )?;
+        let termdict_source = self.termdict_composite.open_read(field).expect(
+            "Failed to open field term dictionary in composite file. Is the field indexed?",
+        );
 
-        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)?,
-            postings_file,
-            positions_file,
-            positions_idx_file,
+            TermDictionary::from_source(&termdict_source),
+            postings_source,
+            positions_source,
+            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
@@ -310,13 +295,13 @@ impl SegmentReader {
     }
 
     /// Returns an iterator that will iterate over the alive document ids
-    pub fn doc_ids_alive(&self) -> impl Iterator<Item = DocId> + '_ {
+    pub fn doc_ids_alive<'a>(&'a self) -> impl Iterator<Item = DocId> + 'a {
         (0u32..self.max_doc).filter(move |doc| !self.is_deleted(*doc))
     }
 
     /// Summarize total space usage of this segment.
-    pub fn space_usage(&self) -> io::Result<SegmentSpaceUsage> {
-        Ok(SegmentSpaceUsage::new(
+    pub fn space_usage(&self) -> SegmentSpaceUsage {
+        SegmentSpaceUsage::new(
             self.num_docs(),
             self.termdict_composite.space_usage(),
             self.postings_composite.space_usage(),
@@ -324,12 +309,12 @@ impl SegmentReader {
             self.positions_idx_composite.space_usage(),
             self.fast_fields_readers.space_usage(),
             self.fieldnorm_readers.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),
-        ))
+        )
     }
 }
 
@@ -346,7 +331,7 @@ 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 +339,26 @@ 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::{FileSlice, WritePtr};
+use crate::directory::{ReadOnlySource, 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> {
-        let file_handle = self.get_file_handle(path)?;
-        Ok(FileSlice::new(file_handle))
-    }
+    fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError>;
 
     /// 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 {
-        /// underlying io Error.
-        io_error: io::Error,
-        /// directory we tried to open.
-        directory_path: PathBuf,
-    },
+    IoError(io::Error),
+}
+
+impl From<io::Error> for OpenDirectoryError {
+    fn from(io_err: io::Error) -> Self {
+        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 {
-        /// The underlying `io::Error`.
-        io_error: io::Error,
-        /// File path of the file that tantivy failed to open for write.
-        filepath: PathBuf,
-    },
+    IOError(IOError),
 }
 
-impl OpenWriteError {
-    /// Wraps an io error.
-    pub fn wrap_io_error(io_error: io::Error, filepath: PathBuf) -> Self {
-        Self::IOError { io_error, filepath }
+impl From<IOError> for OpenWriteError {
+    fn from(err: IOError) -> OpenWriteError {
+        OpenWriteError::IOError(err)
     }
 }
+
+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 {
-        /// The underlying `io::Error`.
-        io_error: io::Error,
-        /// File path of the file that tantivy failed to delete.
-        filepath: PathBuf,
-    },
+    IOError(IOError),
+    /// This library doesn't support the index version found on disk
+    IncompatibleIndex(Incompatibility),
+}
+
+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)> {
-        if file.len() < 4 {
+    pub fn extract_footer(source: ReadOnlySource) -> Result<(Footer, ReadOnlySource), io::Error> {
+        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 mut footer_len_bytes = footer_len_file.read_bytes()?;
-        let footer_len = u32::deserialize(&mut footer_len_bytes)? as usize;
-        let (body, footer) = body_footer.split_from_end(footer_len);
-        let mut footer_bytes = footer.read_bytes()?;
-        let footer = Footer::deserialize(&mut footer_bytes)?;
+        let (body_footer, footer_len_bytes) = source.split_from_end(u32::SIZE_IN_BYTES);
+        let footer_len = LittleEndian::read_u32(footer_len_bytes.as_slice()) as usize;
+        let body_len = body_footer.len() - footer_len;
+        let (body, footer_data) = body_footer.split(body_len);
+        let mut cursor = footer_data.as_slice();
+        let footer = Footer::deserialize(&mut cursor)?;
         Ok((footer, body))
     }
 
@@ -115,18 +116,6 @@ impl Footer {
                 }
                 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(())
-            }
             VersionedFooter::UnknownVersion => Err(Incompatibility::IndexMismatch {
                 library_version: library_version.clone(),
                 index_version: self.version.clone(),
@@ -148,31 +137,24 @@ pub enum VersionedFooter {
         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::V2 {
                 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(&2u32, &mut buf)?;
                 BinarySerializable::serialize(crc32, &mut buf)?;
                 BinarySerializable::serialize(compression, &mut buf)?;
             }
-            VersionedFooter::V2 { .. }
-            | VersionedFooter::V1 { .. }
-            | VersionedFooter::UnknownVersion => {
+            VersionedFooter::V1 { .. } | VersionedFooter::UnknownVersion => {
                 return Err(io::Error::new(
                     io::ErrorKind::InvalidInput,
                     "Cannot serialize an unknown versioned footer ",
@@ -201,7 +183,7 @@ 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 && version != 2 {
             return Ok(VersionedFooter::UnknownVersion);
         }
         let crc32 = u32::deserialize(&mut cursor)?;
@@ -211,14 +193,9 @@ impl BinarySerializable for VersionedFooter {
                 crc32,
                 store_compression,
             }
-        } else if version == 2 {
-            VersionedFooter::V2 {
-                crc32,
-                store_compression,
-            }
         } else {
-            assert_eq!(version, 3);
-            VersionedFooter::V3 {
+            assert_eq!(version, 2);
+            VersionedFooter::V2 {
                 crc32,
                 store_compression,
             }
@@ -229,7 +206,6 @@ impl BinarySerializable for VersionedFooter {
 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 +244,7 @@ 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::V2 {
             crc32,
             store_compression: crate::store::COMPRESSION.to_string(),
         });
@@ -295,15 +271,11 @@ 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(), 158);
-        } else {
-            assert_eq!(vec.len(), 167);
-        }
+        assert_eq!(vec.len(), 167);
         let footer = Footer::deserialize(&mut &vec[..]).unwrap();
         assert!(matches!(
            footer.versioned_footer,
-           VersionedFooter::V3 { store_compression, .. }
+           VersionedFooter::V2 { store_compression, .. }
            if store_compression == crate::store::COMPRESSION
         ));
         assert_eq!(&footer.version, crate::version());
@@ -313,7 +285,7 @@ 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::V2 {
             crc32,
             store_compression: "lz4".to_string(),
         });
@@ -325,7 +297,7 @@ mod tests {
     #[test]
     fn footer_length() {
         let crc32 = 1111111u32;
-        let versioned_footer = VersionedFooter::V3 {
+        let versioned_footer = VersionedFooter::V2 {
             crc32,
             store_compression: "lz4".to_string(),
         };
@@ -346,7 +318,7 @@ mod tests {
             // versionned footer length
             12 | 128,
             // index format version
-            3,
+            2,
             0,
             0,
             0,
@@ -365,7 +337,7 @@ 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::V2 {
             crc32: expected_crc,
             store_compression: "lz4".to_string(),
         };

src/directory/managed_directory.rs

@@ -1,11 +1,11 @@
-use crate::core::{MANAGED_FILEPATH, META_FILEPATH};
-use crate::directory::error::{DeleteError, LockError, OpenReadError, OpenWriteError};
+use crate::core::MANAGED_FILEPATH;
+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::{FileSlice, WritePtr};
+use crate::directory::{ReadOnlySource, WritePtr};
 use crate::directory::{WatchCallback, WatchHandle};
 use crate::error::DataCorruption;
 use crate::Directory;
@@ -53,7 +53,7 @@ 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 +86,7 @@ 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 +168,7 @@ 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 +212,7 @@ 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 +223,7 @@ 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 +231,10 @@ 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) =
-            Footer::extract_footer(reader).map_err(|io_error| OpenReadError::IOError {
-                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 (footer, data) = Footer::extract_footer(reader)
+            .map_err(|err| IOError::with_path(path.to_path_buf(), err))?;
         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 +245,35 @@ 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);
-
-        let mut damaged_files = HashSet::new();
-        for path in managed_paths {
+        for path in managed_paths.into_iter() {
             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> {
-        let file_slice = self.open_read(path)?;
-        Ok(Box::new(file_slice))
-    }
-
-    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()))?;
+    fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
+        let read_only_source = self.directory.open_read(path)?;
+        let (footer, reader) = Footer::extract_footer(read_only_source)
+            .map_err(|err| IOError::with_path(path.to_path_buf(), err))?;
         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 +283,7 @@ 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 +296,7 @@ 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 +344,22 @@ 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_path2).unwrap());
+            assert!(managed_directory.exists(test_path1));
+            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_path2).unwrap());
+            assert!(managed_directory.exists(test_path1));
+            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_path2).unwrap());
+            assert!(managed_directory.exists(test_path1));
+            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_path2).unwrap());
+            assert!(!managed_directory.exists(test_path1));
+            assert!(!managed_directory.exists(test_path2));
         }
     }
 
@@ -392,7 +376,7 @@ 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 +384,52 @@ 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 managed_directory = ManagedDirectory::wrap(mmap_directory)?;
-        let mut write = managed_directory.open_write(test_path1)?;
-        write.write_all(&[0u8, 1u8])?;
-        write.terminate()?;
+        let mmap_directory = MmapDirectory::open(&tempdir_path).unwrap();
+        let mut managed_directory = ManagedDirectory::wrap(mmap_directory).unwrap();
+        let mut write = managed_directory.open_write(test_path1).unwrap();
+        write.write_all(&[0u8, 1u8]).unwrap();
+        write.terminate().unwrap();
 
-        let mut write = managed_directory.open_write(test_path2)?;
-        write.write_all(&[3u8, 4u8, 5u8])?;
-        write.terminate()?;
+        let mut write = managed_directory.open_write(test_path2).unwrap();
+        write.write_all(&[3u8, 4u8, 5u8]).unwrap();
+        write.terminate().unwrap();
 
-        let read_file = managed_directory.open_read(test_path2)?.read_bytes()?;
-        assert_eq!(read_file.as_slice(), &[3u8, 4u8, 5u8]);
+        let read_source = managed_directory.open_read(test_path2).unwrap();
+        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)?;
-        file.write_all(&[255u8])?;
-        file.flush()?;
+        let mut file = OpenOptions::new()
+            .write(true)
+            .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 +1,25 @@
 use crate::core::META_FILEPATH;
 use crate::directory::error::LockError;
-use crate::directory::error::{DeleteError, OpenDirectoryError, OpenReadError, OpenWriteError};
-use crate::directory::file_watcher::FileWatcher;
+use crate::directory::error::{
+    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 memmap::Mmap;
+use notify::RawEvent;
+use notify::RecursiveMode;
+use notify::Watcher;
 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 +28,12 @@ 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 +44,17 @@ 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| {
-        if io_err.kind() == io::ErrorKind::NotFound {
-            OpenReadError::FileDoesNotExist(full_path.to_path_buf())
+    let file = File::open(full_path).map_err(|e| {
+        if e.kind() == io::ErrorKind::NotFound {
+            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 +64,7 @@ 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 +85,7 @@ pub struct CacheInfo {
 
 struct MmapCache {
     counters: CacheCounters,
-    cache: HashMap<PathBuf, WeakArcBytes>,
+    cache: HashMap<PathBuf, Weak<BoxedData>>,
 }
 
 impl Default for MmapCache {
@@ -110,7 +119,7 @@ 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 +130,7 @@ 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 +138,63 @@ 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 +216,40 @@ 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 {
         MmapDirectoryInner {
+            root_path,
             mmap_cache: Default::default(),
             _temp_directory: temp_directory,
-            watcher: FileWatcher::new(&root_path.join(*META_FILEPATH)),
-            root_path,
+            watcher: RwLock::new(None),
         }
     }
 
-    fn watch(&self, callback: WatchCallback) -> crate::Result<WatchHandle> {
-        Ok(self.watcher.watch(callback))
+    fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle> {
+        // 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");
+        }
     }
 }
 
@@ -187,11 +272,9 @@ 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)?;
-        Ok(MmapDirectory::new(
-            tempdir.path().to_path_buf(),
-            Some(tempdir),
-        ))
+        let tempdir = TempDir::new().map_err(OpenDirectoryError::IoError)?;
+        let tempdir_path = PathBuf::from(tempdir.path());
+        Ok(MmapDirectory::new(tempdir_path, Some(tempdir)))
     }
 
     /// Opens a MmapDirectory in a directory.
@@ -313,38 +396,8 @@ 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 +407,12 @@ impl Directory for MmapDirectory {
                  on mmap cache while reading {:?}",
                 path
             );
-            let io_err = make_io_err(msg);
-            OpenReadError::wrap_io_error(io_err, path.to_path_buf())
+            IOError::with_path(path.to_owned(), make_io_err(msg))
         })?;
-
-        let owned_bytes = mmap_cache
+        Ok(mmap_cache
             .get_mmap(&full_path)?
-            .map(|mmap_arc| {
-                let mmap_arc_obj = MmapArc(mmap_arc);
-                OwnedBytes::new(mmap_arc_obj)
-            })
-            .unwrap_or_else(OwnedBytes::empty);
-
-        Ok(Box::new(owned_bytes))
+            .map(ReadOnlySource::from)
+            .unwrap_or_else(ReadOnlySource::empty))
     }
 
     /// Any entry associated to the path in the mmap will be
@@ -374,29 +420,25 @@ 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 {
-                io_error: e,
-                filepath: path.to_path_buf(),
-            }),
+            Ok(_) => self
+                .sync_directory()
+                .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 {
-                        io_error: e,
-                        filepath: path.to_path_buf(),
-                    })
+                    Err(IOError::with_path(path.to_owned(), e).into())
                 }
             }
         }
     }
 
-    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 +447,22 @@ impl Directory for MmapDirectory {
             .create_new(true)
             .open(full_path);
 
-        let mut file = open_res.map_err(|io_err| {
-            if io_err.kind() == io::ErrorKind::AlreadyExists {
-                OpenWriteError::FileAlreadyExists(path.to_path_buf())
+        let mut file = open_res.map_err(|err| {
+            if err.kind() == io::ErrorKind::AlreadyExists {
+                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 +473,26 @@ 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| {
-                    OpenReadError::wrap_io_error(io_error, path.to_path_buf())
-                })?;
+                file.read_to_end(&mut buffer)
+                    .map_err(|e| IOError::with_path(path.to_owned(), e))?;
                 Ok(buffer)
             }
-            Err(io_error) => {
-                if io_error.kind() == io::ErrorKind::NotFound {
+            Err(e) => {
+                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)?;
-        self.sync_directory()
+        let meta_file = atomicwrites::AtomicFile::new(full_path, atomicwrites::AllowOverwrite);
+        meta_file.write(|f| f.write_all(data))?;
+        Ok(())
     }
 
     fn acquire_lock(&self, lock: &Lock) -> Result<DirectoryLock, LockError> {
@@ -485,10 +527,12 @@ 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 +545,7 @@ 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 +561,7 @@ 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 +621,27 @@ 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 +652,7 @@ 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

@@ -9,12 +9,10 @@ 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 watch_event_router;
 
 /// Errors specific to the directory module.
@@ -23,14 +21,11 @@ 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 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

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/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;
@@ -12,8 +12,6 @@ use std::path::{Path, PathBuf};
 use std::result;
 use std::sync::{Arc, RwLock};
 
-use super::FileHandle;
-
 /// Writer associated with the `RAMDirectory`
 ///
 /// The Writer just writes a buffer.
@@ -82,17 +80,17 @@ impl TerminatingWrite for VecWriter {
 
 #[derive(Default)]
 struct InnerDirectory {
-    fs: HashMap<PathBuf, FileSlice>,
+    fs: HashMap<PathBuf, ReadOnlySource>,
     watch_router: WatchCallbackList,
 }
 
 impl InnerDirectory {
     fn write(&mut self, path: PathBuf, data: &[u8]) -> bool {
-        let data = FileSlice::from(data.to_vec());
+        let data = ReadOnlySource::new(Vec::from(data));
         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)))
@@ -153,11 +151,11 @@ 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 +163,24 @@ impl RAMDirectory {
 }
 
 impl Directory for RAMDirectory {
-    fn get_file_handle(&self, path: &Path) -> Result<Box<dyn FileHandle>, OpenReadError> {
-        let file_slice = self.open_read(path)?;
-        Ok(Box::new(file_slice))
-    }
-
-    fn open_read(&self, path: &Path) -> result::Result<FileSlice, OpenReadError> {
+    fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
         self.fs.read().unwrap().open_read(path)
     }
 
     fn delete(&self, path: &Path) -> result::Result<(), DeleteError> {
         fail_point!("RAMDirectory::delete", |_| {
-            Err(DeleteError::IOError {
-                io_error: io::Error::from(io::ErrorKind::Other),
-                filepath: path.to_path_buf(),
-            })
+            use crate::directory::error::IOError;
+            let io_error = IOError::from(io::Error::from(io::ErrorKind::Other));
+            Err(DeleteError::from(io_error))
         });
         self.fs.write().unwrap().delete(path)
     }
 
-    fn exists(&self, path: &Path) -> Result<bool, OpenReadError> {
-        Ok(self
-            .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 exists(&self, path: &Path) -> bool {
+        self.fs.read().unwrap().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 +194,10 @@ impl Directory for RAMDirectory {
     }
 
     fn atomic_read(&self, path: &Path) -> Result<Vec<u8>, OpenReadError> {
-        let bytes =
-            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())
+        Ok(self.open_read(path)?.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())
@@ -256,13 +234,13 @@ 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();
-        assert!(directory.persist(&directory_copy).is_ok());
+        let mut directory_copy = RAMDirectory::create();
+        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);
     }

src/directory/read_only_source.rs

@@ -0,0 +1,137 @@
+use crate::common::HasLen;
+use stable_deref_trait::{CloneStableDeref, StableDeref};
+use std::ops::Deref;
+use std::sync::Arc;
+
+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,
+}
+
+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,
+        }
+    }
+}
+
+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,
+        }
+    }
+
+    /// 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,
+        }
+    }
+
+    /// 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/tests.rs

@@ -20,47 +20,45 @@ mod mmap_directory_tests {
     }
 
     #[test]
-    fn test_simple() -> crate::Result<()> {
-        let directory = make_directory();
-        super::test_simple(&directory)
+    fn test_simple() {
+        let mut directory = make_directory();
+        super::test_simple(&mut directory);
     }
 
     #[test]
     fn test_write_create_the_file() {
-        let directory = make_directory();
-        super::test_write_create_the_file(&directory);
+        let mut directory = make_directory();
+        super::test_write_create_the_file(&mut directory);
     }
 
     #[test]
-    fn test_rewrite_forbidden() -> crate::Result<()> {
-        let directory = make_directory();
-        super::test_rewrite_forbidden(&directory)?;
-        Ok(())
+    fn test_rewrite_forbidden() {
+        let mut directory = make_directory();
+        super::test_rewrite_forbidden(&mut directory);
     }
 
     #[test]
-    fn test_directory_delete() -> crate::Result<()> {
-        let directory = make_directory();
-        super::test_directory_delete(&directory)?;
-        Ok(())
+    fn test_directory_delete() {
+        let mut directory = make_directory();
+        super::test_directory_delete(&mut directory);
     }
 
     #[test]
     fn test_lock_non_blocking() {
-        let directory = make_directory();
-        super::test_lock_non_blocking(&directory);
+        let mut directory = make_directory();
+        super::test_lock_non_blocking(&mut directory);
     }
 
     #[test]
     fn test_lock_blocking() {
-        let directory = make_directory();
-        super::test_lock_blocking(&directory);
+        let mut directory = make_directory();
+        super::test_lock_blocking(&mut directory);
     }
 
     #[test]
     fn test_watch() {
-        let directory = make_directory();
-        super::test_watch(&directory);
+        let mut directory = make_directory();
+        super::test_watch(&mut directory);
     }
 }
 
@@ -74,47 +72,45 @@ mod ram_directory_tests {
     }
 
     #[test]
-    fn test_simple() -> crate::Result<()> {
-        let directory = make_directory();
-        super::test_simple(&directory)
+    fn test_simple() {
+        let mut directory = make_directory();
+        super::test_simple(&mut directory);
     }
 
     #[test]
     fn test_write_create_the_file() {
-        let directory = make_directory();
-        super::test_write_create_the_file(&directory);
+        let mut directory = make_directory();
+        super::test_write_create_the_file(&mut directory);
     }
 
     #[test]
-    fn test_rewrite_forbidden() -> crate::Result<()> {
-        let directory = make_directory();
-        super::test_rewrite_forbidden(&directory)?;
-        Ok(())
+    fn test_rewrite_forbidden() {
+        let mut directory = make_directory();
+        super::test_rewrite_forbidden(&mut directory);
     }
 
     #[test]
-    fn test_directory_delete() -> crate::Result<()> {
-        let directory = make_directory();
-        super::test_directory_delete(&directory)?;
-        Ok(())
+    fn test_directory_delete() {
+        let mut directory = make_directory();
+        super::test_directory_delete(&mut directory);
     }
 
     #[test]
     fn test_lock_non_blocking() {
-        let directory = make_directory();
-        super::test_lock_non_blocking(&directory);
+        let mut directory = make_directory();
+        super::test_lock_non_blocking(&mut directory);
     }
 
     #[test]
     fn test_lock_blocking() {
-        let directory = make_directory();
-        super::test_lock_blocking(&directory);
+        let mut directory = make_directory();
+        super::test_lock_blocking(&mut directory);
     }
 
     #[test]
     fn test_watch() {
-        let directory = make_directory();
-        super::test_watch(&directory);
+        let mut directory = make_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());
-    write_file.write_all(&[4])?;
-    write_file.write_all(&[3])?;
-    write_file.write_all(&[7, 3, 5])?;
-    write_file.flush()?;
-    let read_file = directory.open_read(test_path)?.read_bytes()?;
-    assert_eq!(read_file.as_slice(), &[4u8, 3u8, 7u8, 3u8, 5u8]);
-    mem::drop(read_file);
+    {
+        let mut write_file = directory.open_write(test_path).unwrap();
+        assert!(directory.exists(test_path));
+        write_file.write_all(&[4]).unwrap();
+        write_file.write_all(&[3]).unwrap();
+        write_file.write_all(&[7, 3, 5]).unwrap();
+        write_file.flush().unwrap();
+    }
+    {
+        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());
-    Ok(())
+    assert!(!directory.exists(test_path));
 }
 
-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());
-    assert!(directory.open_write(test_path).is_err());
+    {
+        directory.open_write(test_path).unwrap();
+        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)?;
-    write_file.write_all(&[1, 2, 3, 4])?;
-    write_file.flush()?;
+    let mut write_file = directory.open_write(&test_path).unwrap();
+    write_file.write_all(&[1, 2, 3, 4]).unwrap();
+    write_file.flush().unwrap();
     {
-        let read_handle = directory.open_read(&test_path)?.read_bytes()?;
-        assert_eq!(read_handle.as_slice(), &[1u8, 2u8, 3u8, 4u8]);
+        let read_handle = directory.open_read(&test_path).unwrap();
+        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 timeout = Duration::from_millis(500);
-
-    let handle = directory
-        .watch(WatchCallback::new(move || {
-            let val = counter.fetch_add(1, SeqCst);
-            tx.send(val + 1).unwrap();
+    let counter_clone = counter.clone();
+    let (sender, receiver) = crossbeam::channel::unbounded();
+    let watch_callback = Box::new(move || {
+        counter_clone.fetch_add(1, SeqCst);
+    });
+    // This callback is used to synchronize watching in our unit test.
+    // 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!(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());
+    assert!(receiver.recv_timeout(Duration::from_millis(500)).is_ok());
+    assert_eq!(10, counter.load(SeqCst));
 }
 
-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`.
-#[derive(Clone)]
-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()
-    }
-}
+/// Type alias for callbacks registered when watching files of a `Directory`.
+pub type WatchCallback = Box<dyn Fn() + Sync + Send>;
 
 /// Helper struct to implement the watch method in `Directory` implementations.
 ///
@@ -41,13 +29,6 @@ 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 {
@@ -59,13 +40,13 @@ impl WatchCallbackList {
         WatchHandle::new(watch_callback_arc)
     }
 
-    fn list_callback(&self) -> Vec<WatchCallback> {
-        let mut callbacks: Vec<WatchCallback> = vec![];
+    fn list_callback(&self) -> Vec<Arc<WatchCallback>> {
+        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

@@ -10,7 +10,7 @@ use std::borrow::BorrowMut;
 pub const TERMINATED: DocId = std::i32::MAX as u32;
 
 /// Represents an iterable set of sorted doc ids.
-pub trait DocSet: Send {
+pub trait DocSet {
     /// Goes to the next element.
     ///
     /// The DocId of the next element is returned.
@@ -129,14 +129,6 @@ impl<'a> DocSet for &'a mut dyn DocSet {
     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> {

src/error.rs

@@ -2,27 +2,21 @@
 
 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::{
-    directory::error::{OpenDirectoryError, OpenReadError, OpenWriteError},
-    schema,
-};
+use crate::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 +24,10 @@ impl DataCorruption {
         }
     }
 
-    /// Creates a `DataCorruption` Error, when the filepath is irrelevant.
-    pub fn comment_only<TStr: ToString>(comment: TStr) -> DataCorruption {
+    pub fn comment_only(comment: String) -> DataCorruption {
         DataCorruption {
             filepath: None,
-            comment: comment.to_string(),
+            comment,
         }
     }
 }
@@ -50,47 +43,44 @@ impl fmt::Debug for DataCorruption {
     }
 }
 
-/// The library's error enum
-#[derive(Debug, Error)]
+/// The library's failure based error enum
+#[derive(Debug, Fail)]
 pub enum TantivyError {
-    /// Failed to open the directory.
-    #[error("Failed to open the directory: '{0:?}'")]
-    OpenDirectoryError(#[from] OpenDirectoryError),
-    /// Failed to open a file for read.
-    #[error("Failed to open file for read: '{0:?}'")]
-    OpenReadError(#[from] OpenReadError),
-    /// Failed to open a file for write.
-    #[error("Failed to open file for write: '{0:?}'")]
-    OpenWriteError(#[from] OpenWriteError),
+    /// Path does not exist.
+    #[fail(display = "Path does not exist: '{:?}'", _0)]
+    PathDoesNotExist(PathBuf),
+    /// File already exists, this is a problem when we try to write into a new file.
+    #[fail(display = "File already exists: '{:?}'", _0)]
+    FileAlreadyExists(PathBuf),
     /// 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}'")]
-    IOError(#[from] io::Error),
+    #[fail(display = "An IO error occurred: '{}'", _0)]
+    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 +89,31 @@ 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 +126,15 @@ impl<Guard> From<PoisonError<Guard>> for TantivyError {
     }
 }
 
-impl From<chrono::ParseError> for TantivyError {
-    fn from(err: chrono::ParseError) -> TantivyError {
-        TantivyError::InvalidArgument(err.to_string())
+impl From<OpenReadError> for TantivyError {
+    fn from(error: OpenReadError) -> TantivyError {
+        match error {
+            OpenReadError::FileDoesNotExist(filepath) => TantivyError::PathDoesNotExist(filepath),
+            OpenReadError::IOError(io_error) => TantivyError::IOError(io_error),
+            OpenReadError::IncompatibleIndex(incompatibility) => {
+                TantivyError::IncompatibleIndex(incompatibility)
+            }
+        }
     }
 }
 
@@ -134,9 +144,35 @@ 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::{query::TermQuery, schema::FAST, schema::INDEXED, schema::STORED};
-    use crate::{DocAddress, DocSet, Index, Searcher, Term};
-    use std::ops::Deref;
+    use crate::schema::Schema;
+    use crate::Index;
 
     #[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()?;
-        index_writer.add_document(doc!(bytes_field=>vec![0u8, 1, 2, 3]));
-        index_writer.add_document(doc!(bytes_field=>vec![]));
-        index_writer.add_document(doc!(bytes_field=>vec![255u8]));
-        index_writer.add_document(doc!(bytes_field=>vec![1u8, 3, 5, 7, 9]));
-        index_writer.add_document(doc!(bytes_field=>vec![0u8; 1000]));
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(field=>vec![0u8, 1, 2, 3]));
+        index_writer.add_document(doc!(field=>vec![]));
+        index_writer.add_document(doc!(field=>vec![255u8]));
+        index_writer.add_document(doc!(field=>vec![1u8, 3, 5, 7, 9]));
+        index_writer.add_document(doc!(field=>vec![0u8; 1000]));
+        assert!(index_writer.commit().is_ok());
+        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 crate::directory::OwnedBytes;
+use owning_ref::OwningRef;
+
+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,
-    ) -> crate::Result<BytesFastFieldReader> {
-        let values = values_file.read_bytes()?;
-        Ok(BytesFastFieldReader { idx_reader, values })
+        values_source: ReadOnlySource,
+    ) -> BytesFastFieldReader {
+        let values = OwningRef::new(values_source).map(|source| &source[..]);
+        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) {
-            if let Value::Bytes(ref bytes) = field_value {
-                self.vals.extend_from_slice(bytes);
-                return;
+        for field_value in doc.field_values() {
+            if field_value.field() == self.field {
+                if let Value::Bytes(ref bytes) = *field_value.value() {
+                    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 =
-            serializer.new_u64_fast_field_with_idx(self.field, 0, self.vals.len() as u64, 0)?;
-        for &offset in &self.doc_index {
-            doc_index_serializer.add_val(offset)?;
+        {
+            // writing the offset index
+            let mut doc_index_serializer =
+                serializer.new_u64_fast_field_with_idx(self.field, 0, self.vals.len() as u64, 0)?;
+            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::OwnedBytes;
+use crate::directory::ReadOnlySource;
 use crate::directory::WritePtr;
 use crate::space_usage::ByteCount;
 use crate::DocId;
@@ -40,7 +39,7 @@ pub fn write_delete_bitset(
 /// Set of deleted `DocId`s.
 #[derive(Clone)]
 pub struct DeleteBitSet {
-    data: OwnedBytes,
+    data: ReadOnlySource,
     len: usize,
 }
 
@@ -54,27 +53,26 @@ impl DeleteBitSet {
         for &doc in docs {
             bitset.insert(doc);
         }
-        let directory = RAMDirectory::create();
+        let mut 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()
+        let source = directory.open_read(path).unwrap();
+        Self::open(source)
     }
 
-    /// 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
+    /// Opens a delete bitset given its data source.
+    pub fn open(data: ReadOnlySource) -> DeleteBitSet {
+        let num_deleted: usize = data
             .as_slice()
             .iter()
             .map(|b| b.count_ones() as usize)
             .sum();
-        Ok(DeleteBitSet {
-            data: bytes,
+        DeleteBitSet {
+            data,
             len: num_deleted,
-        })
+        }
     }
 
     /// Returns true iff the document is still "alive". In other words, if it has not been deleted.
@@ -86,7 +84,7 @@ 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
     }

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)]
-#[error("Fast field not available: '{field_name:?}'")]
+#[derive(Debug, Fail)]
+#[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[..])
-            .map_err(|utf8_err| DataCorruption::comment_only(utf8_err.to_string()))?;
+        let facet_str = str::from_utf8(&self.buffer[..])?;
         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();
-        assert_eq!(file.len(), 36 as usize);
-        let composite_file = CompositeFile::open(&file)?;
-        let file = composite_file.open_read(*FIELD).unwrap();
-        let fast_field_reader = FastFieldReader::<u64>::open(file)?;
-        assert_eq!(fast_field_reader.get(0), 13u64);
-        assert_eq!(fast_field_reader.get(1), 14u64);
-        assert_eq!(fast_field_reader.get(2), 2u64);
-        Ok(())
+        let source = directory.open_read(&path).unwrap();
+        {
+            assert_eq!(source.len(), 36 as usize);
+        }
+        {
+            let composite_file = CompositeFile::open(&source).unwrap();
+            let field_source = composite_file.open_read(*FIELD).unwrap();
+            let fast_field_reader = FastFieldReader::<u64>::open(field_source);
+            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 mut serializer = FastFieldSerializer::from_write(write)?;
+            let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
+            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())?;
-            serializer.close()?;
+            fast_field_writers
+                .serialize(&mut serializer, &HashMap::new())
+                .unwrap();
+            serializer.close().unwrap();
         }
-        let file = directory.open_read(&path)?;
-        assert_eq!(file.len(), 61 as usize);
+        let source = directory.open_read(&path).unwrap();
         {
-            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();
-        assert_eq!(file.len(), 34 as usize);
+        let source = directory.open_read(&path).unwrap();
         {
-            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();
-        assert_eq!(file.len(), 80042 as usize);
+        let source = directory.open_read(&path).unwrap();
         {
-            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();
-        assert_eq!(file.len(), 17709 as usize);
+        let source = directory.open_read(&path).unwrap();
         {
-            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 mut serializer = FastFieldSerializer::from_write(write)?;
+            let write: WritePtr = directory.open_write(Path::new("test")).unwrap();
+            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())?;
-            serializer.close()?;
+            fast_field_writers
+                .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(0, &mut vals);
-        assert_eq!(&vals, &[1i64, 3i64]);
-        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]);
+        {
+            multi_value_reader.get_vals(2, &mut vals);
+            assert_eq!(&vals, &[-4i64]);
+        }
+        {
+            multi_value_reader.get_vals(0, &mut vals);
+            assert_eq!(&vals, &[1i64, 3i64]);
+        }
+        {
+            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.
-    pub fn open(file: FileSlice) -> crate::Result<Self> {
-        let mut bytes = file.read_bytes()?;
-        let min_value = u64::deserialize(&mut bytes)?;
-        let amplitude = u64::deserialize(&mut bytes)?;
+    /// Opens a fast field given a source.
+    pub fn open(data: ReadOnlySource) -> Self {
+        let min_value: u64;
+        let amplitude: u64;
+        {
+            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);
-        Ok(FastFieldReader {
+        let owning_ref = OwningRef::new(data).map(|data| &data[16..]);
+        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 composite_file = CompositeFile::open(&file).expect("Failed to read the composite file");
-        let field_file = composite_file
+        let source = directory.open_read(path).expect("Failed to open the file");
+        let 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 !bytes_option.is_fast() {
-                    continue;
-                }
-                let fast_field_idx_file = fast_fields_composite
+            if field_type == &FieldType::Bytes {
+                let idx_reader = fast_fields_composite
                     .open_read_with_idx(field, 0)
-                    .ok_or_else(|| FastFieldNotAvailableError::new(field_entry))?;
-                let idx_reader = FastFieldReader::open(fast_field_idx_file)?;
+                    .ok_or_else(|| FastFieldNotAvailableError::new(field_entry))
+                    .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 =
-                                        FastFieldReader::open(fast_field_data.clone())?;
-                                    fast_field_readers
-                                        .fast_field_i64
-                                        .insert(field, fast_field_reader);
+                                    fast_field_readers.fast_field_i64.insert(
+                                        field,
+                                        FastFieldReader::open(fast_field_data.clone()),
+                                    );
                                 }
                                 FastType::F64 => {
-                                    let fast_field_reader =
-                                        FastFieldReader::open(fast_field_data.clone())?;
-                                    fast_field_readers
-                                        .fast_field_f64
-                                        .insert(field, fast_field_reader);
+                                    fast_field_readers.fast_field_f64.insert(
+                                        field,
+                                        FastFieldReader::open(fast_field_data.clone()),
+                                    );
                                 }
                                 FastType::Date => {
-                                    let fast_field_reader =
-                                        FastFieldReader::open(fast_field_data.clone())?;
-                                    fast_field_readers
-                                        .fast_field_date
-                                        .insert(field, fast_field_reader);
+                                    fast_field_readers.fast_field_date.insert(
+                                        field,
+                                        FastFieldReader::open(fast_field_data.clone()),
+                                    );
                                 }
                             }
                         } 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) => {
-                    if bytes_option.is_fast() {
-                        let fast_field_writer = BytesFastFieldWriter::new(field);
-                        bytes_value_writers.push(fast_field_writer);
-                    }
+                FieldType::Bytes => {
+                    let fast_field_writer = BytesFastFieldWriter::new(field);
+                    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/reader.rs

@@ -1,7 +1,6 @@
 use super::{fieldnorm_to_id, id_to_fieldnorm};
 use crate::common::CompositeFile;
-use crate::directory::FileSlice;
-use crate::directory::OwnedBytes;
+use crate::directory::ReadOnlySource;
 use crate::schema::Field;
 use crate::space_usage::PerFieldSpaceUsage;
 use crate::DocId;
@@ -20,21 +19,16 @@ pub struct FieldNormReaders {
 
 impl FieldNormReaders {
     /// Creates a field norm reader.
-    pub fn open(file: FileSlice) -> crate::Result<FieldNormReaders> {
-        let data = CompositeFile::open(&file)?;
+    pub fn open(source: ReadOnlySource) -> crate::Result<FieldNormReaders> {
+        let data = CompositeFile::open(&source)?;
         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)
-        }
+    pub fn get_field(&self, field: Field) -> Option<FieldNormReader> {
+        self.data.open_read(field).map(FieldNormReader::open)
     }
 
     /// Return a break down of the space usage per field.
@@ -61,56 +55,19 @@ impl FieldNormReaders {
 /// precompute computationally expensive functions of the fieldnorm
 /// in a very short array.
 #[derive(Clone)]
-pub struct FieldNormReader(ReaderImplEnum);
-
-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,
-    },
+pub struct FieldNormReader {
+    data: ReadOnlySource,
 }
 
 impl FieldNormReader {
-    /// Creates a `FieldNormReader` with a constant fieldnorm.
-    ///
-    /// The fieldnorm will be subjected to compression as if it was coming
-    /// 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()
+    /// Opens a field norm reader given its data source.
+    pub fn open(data: ReadOnlySource) -> Self {
+        FieldNormReader { data }
     }
 
     /// 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,
-        }
+        self.data.len() as u32
     }
 
     /// Returns the `fieldnorm` associated to a doc id.
@@ -123,25 +80,15 @@ 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 {
-            ReaderImplEnum::FromData(data) => {
-                let fieldnorm_id = data.as_slice()[doc_id as usize];
-                id_to_fieldnorm(fieldnorm_id)
-            }
-            ReaderImplEnum::Const { fieldnorm, .. } => *fieldnorm,
-        }
+        let fieldnorm_id = self.fieldnorm_id(doc_id);
+        id_to_fieldnorm(fieldnorm_id)
     }
 
     /// Returns the `fieldnorm_id` associated to a document.
     #[inline(always)]
     pub fn fieldnorm_id(&self, doc_id: DocId) -> u8 {
-        match &self.0 {
-            ReaderImplEnum::FromData(data) => {
-                let fieldnorm_id = data.as_slice()[doc_id as usize];
-                fieldnorm_id
-            }
-            ReaderImplEnum::Const { fieldnorm_id, .. } => *fieldnorm_id,
-        }
+        let fielnorms_data = self.data.as_slice();
+        fielnorms_data[doc_id as usize]
     }
 
     /// Converts a `fieldnorm_id` into a fieldnorm.
@@ -164,8 +111,10 @@ impl FieldNormReader {
             .cloned()
             .map(FieldNormReader::fieldnorm_to_id)
             .collect::<Vec<u8>>();
-        let field_norms_data = OwnedBytes::new(field_norms_id);
-        FieldNormReader::new(field_norms_data)
+        let field_norms_data = ReadOnlySource::from(field_norms_id);
+        FieldNormReader {
+            data: field_norms_data,
+        }
     }
 }
 
@@ -184,20 +133,4 @@ mod tests {
         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)
-                .take(max_field)
-                .collect::<Vec<_>>(),
+            fieldnorms_buffer: (0..max_field).map(|_| Vec::new()).collect::<Vec<_>>(),
         }
     }
 

src/functional_test.rs

@@ -31,7 +31,7 @@ fn test_indexing() {
     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().expect("Commit failed");
             committed_docs.extend(&uncommitted_docs);

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

@@ -108,9 +108,9 @@ 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 deleted_doc != TERMINATED {
@@ -449,7 +449,7 @@ 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()
     }
 
@@ -800,7 +800,7 @@ 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 +815,7 @@ 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 +864,7 @@ 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 +926,8 @@ 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();
-        match index.writer_for_tests() {
+        let _index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        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 +979,7 @@ 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 +1015,7 @@ 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
@@ -1110,7 +1110,6 @@ 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 +1129,7 @@ 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 +1180,7 @@ mod tests {
 
         // working with an empty index == no documents
         let term_b = Term::from_field_text(text_field, "b");
-        assert_eq!(
-            index
-                .reader()
-                .unwrap()
-                .searcher()
-                .doc_freq(&term_b)
-                .unwrap(),
-            0
-        );
+        assert_eq!(index.reader().unwrap().searcher().doc_freq(&term_b), 0);
     }
 
     #[test]
@@ -1209,15 +1200,7 @@ 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!(
-            index
-                .reader()
-                .unwrap()
-                .searcher()
-                .doc_freq(&term_a)
-                .unwrap(),
-            1
-        );
+        assert_eq!(index.reader().unwrap().searcher().doc_freq(&term_a), 1);
     }
 
     #[test]
@@ -1243,15 +1226,7 @@ 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!(
-            index
-                .reader()
-                .unwrap()
-                .searcher()
-                .doc_freq(&term_a)
-                .unwrap(),
-            1
-        );
+        assert_eq!(index.reader().unwrap().searcher().doc_freq(&term_a), 1);
     }
 
     #[test]
@@ -1286,7 +1261,7 @@ 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());

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 {

src/indexer/merger.rs

@@ -25,23 +25,23 @@ use std::cmp;
 use std::collections::HashMap;
 use std::sync::Arc;
 
-fn compute_total_num_tokens(readers: &[SegmentReader], field: Field) -> crate::Result<u64> {
+fn compute_total_num_tokens(readers: &[SegmentReader], field: Field) -> u64 {
     let mut total_tokens = 0u64;
     let mut count: [usize; 256] = [0; 256];
     for reader in readers {
         if reader.has_deletes() {
             // if there are deletes, then we use an approximation
             // using the fieldnorm
-            let fieldnorms_reader = reader.get_fieldnorms_reader(field)?;
+            let fieldnorms_reader = reader.get_fieldnorms_reader(field);
             for doc in reader.doc_ids_alive() {
                 let fieldnorm_id = fieldnorms_reader.fieldnorm_id(doc);
                 count[fieldnorm_id as usize] += 1;
             }
         } else {
-            total_tokens += reader.inverted_index(field)?.total_num_tokens();
+            total_tokens += reader.inverted_index(field).total_num_tokens();
         }
     }
-    Ok(total_tokens
+    total_tokens
         + count
             .iter()
             .cloned()
@@ -49,7 +49,7 @@ fn compute_total_num_tokens(readers: &[SegmentReader], field: Field) -> crate::R
             .map(|(fieldnorm_ord, count)| {
                 count as u64 * u64::from(FieldNormReader::id_to_fieldnorm(fieldnorm_ord as u8))
             })
-            .sum::<u64>())
+            .sum::<u64>()
 }
 
 pub struct IndexMerger {
@@ -175,7 +175,7 @@ impl IndexMerger {
         for field in fields {
             fieldnorms_data.clear();
             for reader in &self.readers {
-                let fieldnorms_reader = reader.get_fieldnorms_reader(field)?;
+                let fieldnorms_reader = reader.get_fieldnorms_reader(field);
                 for doc_id in reader.doc_ids_alive() {
                     let fieldnorm_id = fieldnorms_reader.fieldnorm_id(doc_id);
                     fieldnorms_data.push(fieldnorm_id);
@@ -194,7 +194,7 @@ impl IndexMerger {
     ) -> crate::Result<()> {
         for (field, field_entry) in self.schema.fields() {
             let field_type = field_entry.field_type();
-            match field_type {
+            match *field_type {
                 FieldType::HierarchicalFacet => {
                     let term_ordinal_mapping = term_ord_mappings
                         .remove(&field)
@@ -223,10 +223,8 @@ impl IndexMerger {
                     // They can be implemented using what is done
                     // for facets in the future.
                 }
-                FieldType::Bytes(byte_options) => {
-                    if byte_options.is_fast() {
-                        self.write_bytes_fast_field(field, fast_field_serializer)?;
-                    }
+                FieldType::Bytes => {
+                    self.write_bytes_fast_field(field, fast_field_serializer)?;
                 }
             }
         }
@@ -445,11 +443,9 @@ impl IndexMerger {
         let mut bytes_readers: Vec<BytesFastFieldReader> = Vec::new();
 
         for reader in &self.readers {
-            let bytes_reader = reader.fast_fields().bytes(field).ok_or_else(|| {
-                crate::TantivyError::InvalidArgument(
-                    "Bytes fast field {:?} not found in segment.".to_string(),
-                )
-            })?;
+            let bytes_reader = reader.fast_fields().bytes(field).expect(
+                "Failed to find bytes fast field reader. This is a bug in tantivy, please report.",
+            );
             if let Some(delete_bitset) = reader.delete_bitset() {
                 for doc in 0u32..reader.max_doc() {
                     if delete_bitset.is_alive(doc) {
@@ -502,19 +498,18 @@ impl IndexMerger {
     ) -> crate::Result<Option<TermOrdinalMapping>> {
         let mut positions_buffer: Vec<u32> = Vec::with_capacity(1_000);
         let mut delta_computer = DeltaComputer::new();
-
-        let mut max_term_ords: Vec<TermOrdinal> = Vec::new();
-
         let field_readers: Vec<Arc<InvertedIndexReader>> = self
             .readers
             .iter()
             .map(|reader| reader.inverted_index(indexed_field))
-            .collect::<crate::Result<Vec<_>>>()?;
+            .collect::<Vec<_>>();
 
         let mut field_term_streams = Vec::new();
+        let mut max_term_ords: Vec<TermOrdinal> = Vec::new();
+
         for field_reader in &field_readers {
             let terms = field_reader.terms();
-            field_term_streams.push(terms.stream()?);
+            field_term_streams.push(terms.stream());
             max_term_ords.push(terms.num_terms() as u64);
         }
 
@@ -546,7 +541,7 @@ impl IndexMerger {
         // The total number of tokens will only be exact when there has been no deletes.
         //
         // Otherwise, we approximate by removing deleted documents proportionally.
-        let total_num_tokens: u64 = compute_total_num_tokens(&self.readers, indexed_field)?;
+        let total_num_tokens: u64 = compute_total_num_tokens(&self.readers, indexed_field);
 
         // Create the total list of doc ids
         // by stacking the doc ids from the different segment.
@@ -583,8 +578,8 @@ impl IndexMerger {
                 let term_info = heap_item.streamer.value();
                 let segment_reader = &self.readers[heap_item.segment_ord];
                 let inverted_index: &InvertedIndexReader = &*field_readers[segment_ord];
-                let segment_postings = inverted_index
-                    .read_postings_from_terminfo(term_info, segment_postings_option)?;
+                let segment_postings =
+                    inverted_index.read_postings_from_terminfo(term_info, segment_postings_option);
                 let delete_bitset_opt = segment_reader.delete_bitset();
                 let doc_freq = if let Some(delete_bitset) = delete_bitset_opt {
                     segment_postings.doc_freq_given_deletes(delete_bitset)
@@ -653,7 +648,7 @@ impl IndexMerger {
     ) -> crate::Result<HashMap<Field, TermOrdinalMapping>> {
         let mut term_ordinal_mappings = HashMap::new();
         for (field, field_entry) in self.schema.fields() {
-            let fieldnorm_reader = fieldnorm_readers.get_field(field)?;
+            let fieldnorm_reader = fieldnorm_readers.get_field(field);
             if field_entry.is_indexed() {
                 if let Some(term_ordinal_mapping) = self.write_postings_for_field(
                     field,
@@ -670,7 +665,7 @@ impl IndexMerger {
 
     fn write_storable_fields(&self, store_writer: &mut StoreWriter) -> crate::Result<()> {
         for reader in &self.readers {
-            let store_reader = reader.get_store_reader()?;
+            let store_reader = reader.get_store_reader();
             if reader.num_deleted_docs() > 0 {
                 for doc_id in reader.doc_ids_alive() {
                     let doc = store_reader.get(doc_id)?;
@@ -725,12 +720,12 @@ mod tests {
     use crate::IndexWriter;
     use crate::Searcher;
     use crate::{schema, DocSet, SegmentId};
-    use byteorder::{BigEndian, ReadBytesExt};
+    use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
     use futures::executor::block_on;
-    use schema::FAST;
+    use std::io::Cursor;
 
     #[test]
-    fn test_index_merger_no_deletes() -> crate::Result<()> {
+    fn test_index_merger_no_deletes() {
         let mut schema_builder = schema::Schema::builder();
         let text_fieldtype = schema::TextOptions::default()
             .set_indexing_options(
@@ -743,77 +738,98 @@ mod tests {
         let date_field = schema_builder.add_date_field("date", INDEXED);
         let score_fieldtype = schema::IntOptions::default().set_fast(Cardinality::SingleValue);
         let score_field = schema_builder.add_u64_field("score", score_fieldtype);
-        let bytes_score_field = schema_builder.add_bytes_field("score_bytes", FAST);
+        let bytes_score_field = schema_builder.add_bytes_field("score_bytes");
         let index = Index::create_in_ram(schema_builder.build());
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let curr_time = chrono::Utc::now();
-        {
-            let mut index_writer = index.writer_for_tests()?;
-            // writing the segment
-            index_writer.add_document(doc!(
-                text_field => "af b",
-                score_field => 3u64,
-                date_field => curr_time,
-                bytes_score_field => 3u32.to_be_bytes().as_ref()
-            ));
+        let add_score_bytes = |doc: &mut Document, score: u32| {
+            let mut bytes = Vec::new();
+            bytes
+                .write_u32::<BigEndian>(score)
+                .expect("failed to write u32 bytes to Vec...");
+            doc.add_bytes(bytes_score_field, bytes);
+        };
 
-            index_writer.add_document(doc!(
-                text_field => "a b c",
-                score_field => 5u64,
-                bytes_score_field => 5u32.to_be_bytes().as_ref()
-            ));
-            index_writer.add_document(doc!(
-                text_field => "a b c d",
-                score_field => 7u64,
-                bytes_score_field => 7u32.to_be_bytes().as_ref()
-            ));
-            index_writer.commit()?;
-            // writing the segment
-            index_writer.add_document(doc!(
-                text_field => "af b",
-                date_field => curr_time,
-                score_field => 11u64,
-                bytes_score_field => 11u32.to_be_bytes().as_ref()
-            ));
-            index_writer.add_document(doc!(
-                text_field => "a b c g",
-                score_field => 13u64,
-                bytes_score_field => 13u32.to_be_bytes().as_ref()
-            ));
-            index_writer.commit()?;
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            {
+                // writing the segment
+                {
+                    let mut doc = Document::default();
+                    doc.add_text(text_field, "af b");
+                    doc.add_u64(score_field, 3);
+                    doc.add_date(date_field, &curr_time);
+                    add_score_bytes(&mut doc, 3);
+                    index_writer.add_document(doc);
+                }
+                {
+                    let mut doc = Document::default();
+                    doc.add_text(text_field, "a b c");
+                    doc.add_u64(score_field, 5);
+                    add_score_bytes(&mut doc, 5);
+                    index_writer.add_document(doc);
+                }
+                {
+                    let mut doc = Document::default();
+                    doc.add_text(text_field, "a b c d");
+                    doc.add_u64(score_field, 7);
+                    add_score_bytes(&mut doc, 7);
+                    index_writer.add_document(doc);
+                }
+                index_writer.commit().expect("committed");
+            }
+
+            {
+                // writing the segment
+                {
+                    let mut doc = Document::default();
+                    doc.add_text(text_field, "af b");
+                    doc.add_date(date_field, &curr_time);
+                    doc.add_u64(score_field, 11);
+                    add_score_bytes(&mut doc, 11);
+                    index_writer.add_document(doc);
+                }
+                {
+                    let mut doc = Document::default();
+                    doc.add_text(text_field, "a b c g");
+                    doc.add_u64(score_field, 13);
+                    add_score_bytes(&mut doc, 13);
+                    index_writer.add_document(doc);
+                }
+                index_writer.commit().expect("Commit failed");
+            }
         }
         {
             let segment_ids = index
                 .searchable_segment_ids()
                 .expect("Searchable segments failed.");
-            let mut index_writer = index.writer_for_tests()?;
-            block_on(index_writer.merge(&segment_ids))?;
-            index_writer.wait_merging_threads()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            block_on(index_writer.merge(&segment_ids)).expect("Merging failed");
+            index_writer.wait_merging_threads().unwrap();
         }
         {
-            reader.reload()?;
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             let get_doc_ids = |terms: Vec<Term>| {
                 let query = BooleanQuery::new_multiterms_query(terms);
-                searcher
-                    .search(&query, &TEST_COLLECTOR_WITH_SCORE)
-                    .map(|top_docs| top_docs.docs().to_vec())
+                let top_docs = searcher.search(&query, &TEST_COLLECTOR_WITH_SCORE).unwrap();
+                top_docs.docs().to_vec()
             };
             {
                 assert_eq!(
-                    get_doc_ids(vec![Term::from_field_text(text_field, "a")])?,
+                    get_doc_ids(vec![Term::from_field_text(text_field, "a")]),
                     vec![DocAddress(0, 1), DocAddress(0, 2), DocAddress(0, 4)]
                 );
                 assert_eq!(
-                    get_doc_ids(vec![Term::from_field_text(text_field, "af")])?,
+                    get_doc_ids(vec![Term::from_field_text(text_field, "af")]),
                     vec![DocAddress(0, 0), DocAddress(0, 3)]
                 );
                 assert_eq!(
-                    get_doc_ids(vec![Term::from_field_text(text_field, "g")])?,
+                    get_doc_ids(vec![Term::from_field_text(text_field, "g")]),
                     vec![DocAddress(0, 4)]
                 );
                 assert_eq!(
-                    get_doc_ids(vec![Term::from_field_text(text_field, "b")])?,
+                    get_doc_ids(vec![Term::from_field_text(text_field, "b")]),
                     vec![
                         DocAddress(0, 0),
                         DocAddress(0, 1),
@@ -823,57 +839,60 @@ mod tests {
                     ]
                 );
                 assert_eq!(
-                    get_doc_ids(vec![Term::from_field_date(date_field, &curr_time)])?,
+                    get_doc_ids(vec![Term::from_field_date(date_field, &curr_time)]),
                     vec![DocAddress(0, 0), DocAddress(0, 3)]
                 );
             }
             {
-                let doc = searcher.doc(DocAddress(0, 0))?;
+                let doc = searcher.doc(DocAddress(0, 0)).unwrap();
                 assert_eq!(doc.get_first(text_field).unwrap().text(), Some("af b"));
             }
             {
-                let doc = searcher.doc(DocAddress(0, 1))?;
+                let doc = searcher.doc(DocAddress(0, 1)).unwrap();
                 assert_eq!(doc.get_first(text_field).unwrap().text(), Some("a b c"));
             }
             {
-                let doc = searcher.doc(DocAddress(0, 2))?;
+                let doc = searcher.doc(DocAddress(0, 2)).unwrap();
                 assert_eq!(doc.get_first(text_field).unwrap().text(), Some("a b c d"));
             }
             {
-                let doc = searcher.doc(DocAddress(0, 3))?;
+                let doc = searcher.doc(DocAddress(0, 3)).unwrap();
                 assert_eq!(doc.get_first(text_field).unwrap().text(), Some("af b"));
             }
             {
-                let doc = searcher.doc(DocAddress(0, 4))?;
+                let doc = searcher.doc(DocAddress(0, 4)).unwrap();
                 assert_eq!(doc.get_first(text_field).unwrap().text(), Some("a b c g"));
             }
             {
                 let get_fast_vals = |terms: Vec<Term>| {
                     let query = BooleanQuery::new_multiterms_query(terms);
-                    searcher.search(&query, &FastFieldTestCollector::for_field(score_field))
+                    searcher
+                        .search(&query, &FastFieldTestCollector::for_field(score_field))
+                        .unwrap()
                 };
                 let get_fast_vals_bytes = |terms: Vec<Term>| {
                     let query = BooleanQuery::new_multiterms_query(terms);
-                    searcher.search(
-                        &query,
-                        &BytesFastFieldTestCollector::for_field(bytes_score_field),
-                    )
+                    searcher
+                        .search(
+                            &query,
+                            &BytesFastFieldTestCollector::for_field(bytes_score_field),
+                        )
+                        .expect("failed to search")
                 };
                 assert_eq!(
-                    get_fast_vals(vec![Term::from_field_text(text_field, "a")])?,
+                    get_fast_vals(vec![Term::from_field_text(text_field, "a")]),
                     vec![5, 7, 13]
                 );
                 assert_eq!(
-                    get_fast_vals_bytes(vec![Term::from_field_text(text_field, "a")])?,
+                    get_fast_vals_bytes(vec![Term::from_field_text(text_field, "a")]),
                     vec![0, 0, 0, 5, 0, 0, 0, 7, 0, 0, 0, 13]
                 );
             }
         }
-        Ok(())
     }
 
     #[test]
-    fn test_index_merger_with_deletes() -> crate::Result<()> {
+    fn test_index_merger_with_deletes() {
         let mut schema_builder = schema::Schema::builder();
         let text_fieldtype = schema::TextOptions::default()
             .set_indexing_options(
@@ -883,26 +902,27 @@ mod tests {
         let text_field = schema_builder.add_text_field("text", text_fieldtype);
         let score_fieldtype = schema::IntOptions::default().set_fast(Cardinality::SingleValue);
         let score_field = schema_builder.add_u64_field("score", score_fieldtype);
-        let bytes_score_field = schema_builder.add_bytes_field("score_bytes", FAST);
+        let bytes_score_field = schema_builder.add_bytes_field("score_bytes");
         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();
         let reader = index.reader().unwrap();
         let search_term = |searcher: &Searcher, term: Term| {
             let collector = FastFieldTestCollector::for_field(score_field);
             let bytes_collector = BytesFastFieldTestCollector::for_field(bytes_score_field);
             let term_query = TermQuery::new(term, IndexRecordOption::Basic);
-            searcher
+            let (scores, bytes) = searcher
                 .search(&term_query, &(collector, bytes_collector))
-                .map(|(scores, bytes)| {
-                    let mut score_bytes = &bytes[..];
-                    for &score in &scores {
-                        assert_eq!(score as u32, score_bytes.read_u32::<BigEndian>().unwrap());
-                    }
-                    scores
-                })
+                .unwrap();
+            let mut score_bytes = Cursor::new(bytes);
+            for &score in &scores {
+                assert_eq!(score as u32, score_bytes.read_u32::<BigEndian>().unwrap());
+            }
+
+            scores
         };
 
         let empty_vec = Vec::<u64>::new();
+
         {
             // a first commit
             index_writer.add_document(doc!(
@@ -921,26 +941,26 @@ mod tests {
                 score_field => 3u64,
                 bytes_score_field => vec![0u8, 0, 0, 3],
             ));
-            index_writer.commit()?;
-            reader.reload()?;
+            index_writer.commit().expect("committed");
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             assert_eq!(searcher.num_docs(), 2);
             assert_eq!(searcher.segment_readers()[0].num_docs(), 2);
             assert_eq!(searcher.segment_readers()[0].max_doc(), 3);
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "a"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "a")),
                 vec![1]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "b"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "b")),
                 vec![1]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "c"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "c")),
                 vec![3]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "d"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "d")),
                 vec![1, 3]
             );
         }
@@ -968,8 +988,8 @@ mod tests {
                 score_field => 7_000u64,
                 bytes_score_field => vec![0u8, 0, 27, 88],
             ));
-            index_writer.commit()?;
-            reader.reload()?;
+            index_writer.commit().expect("committed");
+            reader.reload().unwrap();
             let searcher = reader.searcher();
 
             assert_eq!(searcher.segment_readers().len(), 2);
@@ -979,31 +999,31 @@ mod tests {
             assert_eq!(searcher.segment_readers()[1].num_docs(), 1);
             assert_eq!(searcher.segment_readers()[1].max_doc(), 3);
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "a"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "a")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "b"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "b")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "c"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "c")),
                 vec![3]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "d"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "d")),
                 vec![3]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "e"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "e")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "f"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "f")),
                 vec![6_000]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "g"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "g")),
                 vec![6_000, 7_000]
             );
 
@@ -1025,40 +1045,42 @@ mod tests {
         }
         {
             // merging the segments
-            let segment_ids = index.searchable_segment_ids()?;
-            block_on(index_writer.merge(&segment_ids))?;
-            reader.reload()?;
+            let segment_ids = index
+                .searchable_segment_ids()
+                .expect("Searchable segments failed.");
+            block_on(index_writer.merge(&segment_ids)).expect("Merging failed");
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             assert_eq!(searcher.segment_readers().len(), 1);
             assert_eq!(searcher.num_docs(), 3);
             assert_eq!(searcher.segment_readers()[0].num_docs(), 3);
             assert_eq!(searcher.segment_readers()[0].max_doc(), 3);
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "a"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "a")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "b"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "b")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "c"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "c")),
                 vec![3]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "d"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "d")),
                 vec![3]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "e"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "e")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "f"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "f")),
                 vec![6_000]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "g"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "g")),
                 vec![6_000, 7_000]
             );
             let score_field_reader = searcher
@@ -1072,40 +1094,40 @@ mod tests {
         {
             // test a commit with only deletes
             index_writer.delete_term(Term::from_field_text(text_field, "c"));
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
 
-            reader.reload()?;
+            reader.reload().unwrap();
             let searcher = reader.searcher();
             assert_eq!(searcher.segment_readers().len(), 1);
             assert_eq!(searcher.num_docs(), 2);
             assert_eq!(searcher.segment_readers()[0].num_docs(), 2);
             assert_eq!(searcher.segment_readers()[0].max_doc(), 3);
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "a"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "a")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "b"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "b")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "c"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "c")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "d"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "d")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "e"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "e")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "f"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "f")),
                 vec![6_000]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "g"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "g")),
                 vec![6_000, 7_000]
             );
             let score_field_reader = searcher
@@ -1118,9 +1140,11 @@ mod tests {
         }
         {
             // Test merging a single segment in order to remove deletes.
-            let segment_ids = index.searchable_segment_ids()?;
-            block_on(index_writer.merge(&segment_ids))?;
-            reader.reload()?;
+            let segment_ids = index
+                .searchable_segment_ids()
+                .expect("Searchable segments failed.");
+            block_on(index_writer.merge(&segment_ids)).expect("Merging failed");
+            reader.reload().unwrap();
 
             let searcher = reader.searcher();
             assert_eq!(searcher.segment_readers().len(), 1);
@@ -1128,31 +1152,31 @@ mod tests {
             assert_eq!(searcher.segment_readers()[0].num_docs(), 2);
             assert_eq!(searcher.segment_readers()[0].max_doc(), 2);
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "a"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "a")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "b"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "b")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "c"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "c")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "d"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "d")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "e"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "e")),
                 empty_vec
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "f"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "f")),
                 vec![6_000]
             );
             assert_eq!(
-                search_term(&searcher, Term::from_field_text(text_field, "g"))?,
+                search_term(&searcher, Term::from_field_text(text_field, "g")),
                 vec![6_000, 7_000]
             );
             let score_field_reader = searcher
@@ -1167,16 +1191,17 @@ mod tests {
         {
             // Test removing all docs
             index_writer.delete_term(Term::from_field_text(text_field, "g"));
-            index_writer.commit()?;
-            let segment_ids = index.searchable_segment_ids()?;
-            reader.reload()?;
+            index_writer.commit().unwrap();
+            let segment_ids = index
+                .searchable_segment_ids()
+                .expect("Searchable segments failed.");
+            reader.reload().unwrap();
 
             let searcher = reader.searcher();
             assert!(segment_ids.is_empty());
             assert!(searcher.segment_readers().is_empty());
             assert_eq!(searcher.num_docs(), 0);
         }
-        Ok(())
     }
 
     #[test]
@@ -1186,7 +1211,7 @@ mod tests {
         let index = Index::create_in_ram(schema_builder.build());
         let reader = index.reader().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 index_doc = |index_writer: &mut IndexWriter, doc_facets: &[&str]| {
                 let mut doc = Document::default();
                 for facet in doc_facets {
@@ -1251,7 +1276,7 @@ mod tests {
             let segment_ids = index
                 .searchable_segment_ids()
                 .expect("Searchable segments failed.");
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             block_on(index_writer.merge(&segment_ids)).expect("Merging failed");
             index_writer.wait_merging_threads().unwrap();
             reader.reload().unwrap();
@@ -1270,7 +1295,7 @@ mod tests {
 
         // Deleting one term
         {
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             let facet = Facet::from_path(vec!["top", "a", "firstdoc"]);
             let facet_term = Term::from_facet(facet_field, &facet);
             index_writer.delete_term(facet_term);
@@ -1295,7 +1320,7 @@ mod tests {
         let mut schema_builder = schema::Schema::builder();
         let int_field = schema_builder.add_u64_field("intvals", INDEXED);
         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!(int_field => 1u64));
         index_writer.commit().expect("commit failed");
         index_writer.add_document(doc!(int_field => 1u64));
@@ -1324,7 +1349,7 @@ mod tests {
         let index = Index::create_in_ram(schema_builder.build());
         let reader = index.reader().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 doc = Document::default();
             doc.add_u64(int_field, 1);
             index_writer.add_document(doc.clone());
@@ -1363,7 +1388,7 @@ mod tests {
         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();
             let index_doc = |index_writer: &mut IndexWriter, int_vals: &[u64]| {
                 let mut doc = Document::default();
                 for &val in int_vals {
@@ -1437,7 +1462,7 @@ mod tests {
             let segment_ids = index
                 .searchable_segment_ids()
                 .expect("Searchable segments failed.");
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             assert!(block_on(index_writer.merge(&segment_ids)).is_ok());
             assert!(index_writer.wait_merging_threads().is_ok());
         }
@@ -1491,7 +1516,7 @@ mod tests {
 
         let index = Index::create_in_ram(builder.build());
 
-        let mut writer = index.writer_for_tests()?;
+        let mut writer = index.writer_with_num_threads(1, 3_000_000)?;
 
         // Make sure we'll attempt to merge every created segment
         let mut policy = crate::indexer::LogMergePolicy::default();
@@ -1523,7 +1548,7 @@ mod tests {
         let mut builder = schema::SchemaBuilder::new();
         let text = builder.add_text_field("text", TEXT);
         let index = Index::create_in_ram(builder.build());
-        let mut writer = index.writer_for_tests()?;
+        let mut writer = index.writer_with_num_threads(1, 3_000_000)?;
         let happy_term = Term::from_field_text(text, "happy");
         let term_query = TermQuery::new(happy_term, IndexRecordOption::WithFreqs);
         for _ in 0..62 {
@@ -1533,7 +1558,7 @@ mod tests {
         let reader = index.reader()?;
         let searcher = reader.searcher();
         let mut term_scorer = term_query
-            .specialized_weight(&searcher, true)?
+            .specialized_weight(&searcher, true)
             .specialized_scorer(searcher.segment_reader(0u32), 1.0)?;
         assert_eq!(term_scorer.doc(), 0);
         assert_nearly_equals!(term_scorer.block_max_score(), 0.0079681855);
@@ -1548,7 +1573,7 @@ mod tests {
         assert_eq!(searcher.segment_readers().len(), 2);
         for segment_reader in searcher.segment_readers() {
             let mut term_scorer = term_query
-                .specialized_weight(&searcher, true)?
+                .specialized_weight(&searcher, true)
                 .specialized_scorer(segment_reader, 1.0)?;
             // the difference compared to before is instrinsic to the bm25 formula. no worries there.
             for doc in segment_reader.doc_ids_alive() {
@@ -1572,7 +1597,7 @@ mod tests {
 
         let segment_reader = searcher.segment_reader(0u32);
         let mut term_scorer = term_query
-            .specialized_weight(&searcher, true)?
+            .specialized_weight(&searcher, true)
             .specialized_scorer(segment_reader, 1.0)?;
         // the difference compared to before is instrinsic to the bm25 formula. no worries there.
         for doc in segment_reader.doc_ids_alive() {

src/indexer/mod.rs

@@ -29,9 +29,8 @@ 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 +39,7 @@ 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/segment_updater.rs

@@ -43,7 +43,7 @@ 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 +64,7 @@ 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.
@@ -154,7 +154,7 @@ 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,
@@ -193,19 +193,19 @@ 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;
     }
 
@@ -450,8 +450,9 @@ impl SegmentUpdater {
             .into_iter()
             .map(|merge_candidate: MergeCandidate| {
                 MergeOperation::new(&self.merge_operations, commit_opstamp, merge_candidate.0)
-            });
-        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) {
@@ -554,7 +555,7 @@ 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 +608,7 @@ 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 +679,7 @@ 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 {

src/indexer/segment_writer.rs

@@ -10,11 +10,14 @@ use crate::schema::FieldType;
 use crate::schema::Schema;
 use crate::schema::Term;
 use crate::schema::Value;
-use crate::tokenizer::PreTokenizedStream;
-use crate::tokenizer::{DynTokenStreamChain, Tokenizer};
-use crate::tokenizer::{FacetTokenizer, TextAnalyzerT, Token};
+use crate::schema::{Field, FieldEntry};
+use crate::tokenizer::{BoxTokenStream, PreTokenizedStream};
+use crate::tokenizer::{FacetTokenizer, TextAnalyzer};
+use crate::tokenizer::{TokenStreamChain, Tokenizer};
 use crate::Opstamp;
 use crate::{DocId, SegmentComponent};
+use std::io;
+use std::str;
 
 /// Computes the initial size of the hash table.
 ///
@@ -22,7 +25,7 @@ use crate::{DocId, SegmentComponent};
 fn initial_table_size(per_thread_memory_budget: usize) -> crate::Result<usize> {
     let table_memory_upper_bound = per_thread_memory_budget / 3;
     if let Some(limit) = (10..)
-        .take_while(|&num_bits| compute_table_size(num_bits) < table_memory_upper_bound)
+        .take_while(|num_bits: &usize| compute_table_size(*num_bits) < table_memory_upper_bound)
         .last()
     {
         Ok(limit.min(19)) // we cap it at 2^19 = 512K.
@@ -44,9 +47,7 @@ pub struct SegmentWriter {
     fast_field_writers: FastFieldsWriter,
     fieldnorms_writer: FieldNormsWriter,
     doc_opstamps: Vec<Opstamp>,
-    // TODO: change type
-    tokenizers: Vec<Option<Box<dyn TextAnalyzerT>>>,
-    term_buffer: Term,
+    tokenizers: Vec<Option<TextAnalyzer>>,
 }
 
 impl SegmentWriter {
@@ -70,17 +71,17 @@ impl SegmentWriter {
         let multifield_postings = MultiFieldPostingsWriter::new(schema, table_num_bits);
         let tokenizers = schema
             .fields()
-            .map(|(_, field_entry)| match field_entry.field_type() {
-                FieldType::Str(text_options) => {
-                    text_options
+            .map(
+                |(_, field_entry): (Field, &FieldEntry)| match field_entry.field_type() {
+                    FieldType::Str(ref text_options) => text_options
                         .get_indexing_options()
                         .and_then(|text_index_option| {
                             let tokenizer_name = &text_index_option.tokenizer();
                             tokenizer_manager.get(tokenizer_name)
-                        })
-                }
-                _ => None,
-            })
+                        }),
+                    _ => None,
+                },
+            )
             .collect();
         Ok(SegmentWriter {
             max_doc: 0,
@@ -90,7 +91,6 @@ impl SegmentWriter {
             fast_field_writers: FastFieldsWriter::from_schema(schema),
             doc_opstamps: Vec::with_capacity(1_000),
             tokenizers,
-            term_buffer: Term::new(),
         })
     }
 
@@ -116,11 +116,7 @@ impl SegmentWriter {
     /// Indexes a new document
     ///
     /// As a user, you should rather use `IndexWriter`'s add_document.
-    pub fn add_document(
-        &mut self,
-        add_operation: AddOperation,
-        schema: &Schema,
-    ) -> crate::Result<()> {
+    pub fn add_document(&mut self, add_operation: AddOperation, schema: &Schema) -> io::Result<()> {
         let doc_id = self.max_doc;
         let mut doc = add_operation.document;
         self.doc_opstamps.push(add_operation.opstamp);
@@ -128,149 +124,125 @@ 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 make_schema_error = || {
-                crate::TantivyError::SchemaError(format!(
-                    "Expected a {:?} for field {:?}",
-                    field_entry.field_type().value_type(),
-                    field_entry.name()
-                ))
-            };
-            if !field_entry.is_indexed() {
+            let field_options = schema.get_field_entry(field);
+            if !field_options.is_indexed() {
                 continue;
             }
-            let (term_buffer, multifield_postings) =
-                (&mut self.term_buffer, &mut self.multifield_postings);
-            match field_entry.field_type() {
+            match *field_options.field_type() {
                 FieldType::HierarchicalFacet => {
-                    term_buffer.set_field(field);
-                    let facets =
-                        field_values
-                            .iter()
-                            .flat_map(|field_value| match field_value.value() {
-                                Value::Facet(ref facet) => Some(facet.encoded_str()),
-                                _ => {
-                                    panic!("Expected hierarchical facet");
-                                }
-                            });
-                    for facet_str in facets {
+                    let facets: Vec<&str> = field_values
+                        .iter()
+                        .flat_map(|field_value| match *field_value.value() {
+                            Value::Facet(ref facet) => Some(facet.encoded_str()),
+                            _ => {
+                                panic!("Expected hierarchical facet");
+                            }
+                        })
+                        .collect();
+                    let mut term = Term::for_field(field); // we set the Term
+                    for fake_str in facets {
                         let mut unordered_term_id_opt = None;
-                        FacetTokenizer
-                            .token_stream(facet_str)
-                            .map(|token| {
-                                term_buffer.set_text(&token.text);
-                                let unordered_term_id =
-                                    multifield_postings.subscribe(doc_id, &term_buffer);
-                                unordered_term_id_opt = Some(unordered_term_id);
-                            })
-                            .count();
+                        FacetTokenizer.token_stream(fake_str).process(&mut |token| {
+                            term.set_text(&token.text);
+                            let unordered_term_id =
+                                self.multifield_postings.subscribe(doc_id, &term);
+                            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);
                         }
                     }
                 }
                 FieldType::Str(_) => {
-                    let mut streams_with_offsets = vec![];
+                    let mut token_streams: Vec<BoxTokenStream> = vec![];
+                    let mut offsets = vec![];
                     let mut total_offset = 0;
 
                     for field_value in field_values {
                         match field_value.value() {
                             Value::PreTokStr(tok_str) => {
-                                streams_with_offsets.push((
-                                    Box::new(PreTokenizedStream::from(tok_str.clone()))
-                                        as Box<dyn Iterator<Item = Token>>,
-                                    total_offset,
-                                ));
+                                offsets.push(total_offset);
                                 if let Some(last_token) = tok_str.tokens.last() {
                                     total_offset += last_token.offset_to;
                                 }
+
+                                token_streams
+                                    .push(PreTokenizedStream::from(tok_str.clone()).into());
                             }
-                            Value::Str(text) => {
+                            Value::Str(ref text) => {
                                 if let Some(ref mut tokenizer) =
                                     self.tokenizers[field.field_id() as usize]
                                 {
-                                    streams_with_offsets
-                                        .push((tokenizer.token_stream(text), total_offset));
+                                    offsets.push(total_offset);
                                     total_offset += text.len();
+
+                                    token_streams.push(tokenizer.token_stream(text));
                                 }
                             }
                             _ => (),
                         }
                     }
 
-                    let num_tokens = if streams_with_offsets.is_empty() {
+                    let num_tokens = if token_streams.is_empty() {
                         0
                     } else {
-                        let mut token_stream = DynTokenStreamChain::from_vec(streams_with_offsets);
-                        multifield_postings.index_text(
-                            doc_id,
-                            field,
-                            &mut token_stream,
-                            term_buffer,
-                        )
+                        let mut token_stream = TokenStreamChain::new(offsets, token_streams);
+                        self.multifield_postings
+                            .index_text(doc_id, field, &mut token_stream)
                     };
 
                     self.fieldnorms_writer.record(doc_id, field, num_tokens);
                 }
-                FieldType::U64(int_option) if int_option.is_indexed() => {
-                    for field_value in field_values {
-                        term_buffer.set_field(field_value.field());
-                        let u64_val = field_value
-                            .value()
-                            .u64_value()
-                            .ok_or_else(make_schema_error)?;
-                        term_buffer.set_u64(u64_val);
-                        multifield_postings.subscribe(doc_id, &term_buffer);
+                FieldType::U64(ref int_option) => {
+                    if int_option.is_indexed() {
+                        for field_value in field_values {
+                            let term = Term::from_field_u64(
+                                field_value.field(),
+                                field_value.value().u64_value(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
+                        }
                     }
                 }
-                FieldType::Date(int_option) if int_option.is_indexed() => {
-                    for field_value in field_values {
-                        term_buffer.set_field(field_value.field());
-                        let date_val = field_value
-                            .value()
-                            .date_value()
-                            .ok_or_else(make_schema_error)?;
-                        term_buffer.set_i64(date_val.timestamp());
-                        multifield_postings.subscribe(doc_id, &term_buffer);
+                FieldType::Date(ref int_option) => {
+                    if int_option.is_indexed() {
+                        for field_value in field_values {
+                            let term = Term::from_field_i64(
+                                field_value.field(),
+                                field_value.value().date_value().timestamp(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
+                        }
                     }
                 }
-                FieldType::I64(int_option) if int_option.is_indexed() => {
-                    for field_value in field_values {
-                        term_buffer.set_field(field_value.field());
-                        let i64_val = field_value
-                            .value()
-                            .i64_value()
-                            .ok_or_else(make_schema_error)?;
-                        term_buffer.set_i64(i64_val);
-                        multifield_postings.subscribe(doc_id, &term_buffer);
+                FieldType::I64(ref int_option) => {
+                    if int_option.is_indexed() {
+                        for field_value in field_values {
+                            let term = Term::from_field_i64(
+                                field_value.field(),
+                                field_value.value().i64_value(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
+                        }
                     }
                 }
-                FieldType::F64(int_option) if int_option.is_indexed() => {
-                    for field_value in field_values {
-                        term_buffer.set_field(field_value.field());
-                        let f64_val = field_value
-                            .value()
-                            .f64_value()
-                            .ok_or_else(make_schema_error)?;
-                        term_buffer.set_f64(f64_val);
-                        multifield_postings.subscribe(doc_id, &term_buffer);
+                FieldType::F64(ref int_option) => {
+                    if int_option.is_indexed() {
+                        for field_value in field_values {
+                            let term = Term::from_field_f64(
+                                field_value.field(),
+                                field_value.value().f64_value(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
+                        }
                     }
                 }
-                FieldType::Bytes(option) if option.is_indexed() => {
-                    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);
-                    }
+                FieldType::Bytes => {
+                    // Do nothing. Bytes only supports fast fields.
                 }
-                _ => {}
             }
         }
         doc.filter_fields(|field| schema.get_field_entry(field).is_stored());

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;
@@ -157,7 +157,6 @@ pub use self::snippet::{Snippet, SnippetGenerator};
 
 mod docset;
 pub use self::docset::{DocSet, TERMINATED};
-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};
@@ -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 = 2;
 
 /// Structure version for the index.
 #[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -246,10 +245,18 @@ pub type DocId = u32;
 /// with opstamp `n+1`.
 pub type Opstamp = u64;
 
+/// A Score that represents the relevance of the document to the query
+///
+/// This is modelled internally as a `f64`, because tantivy was compiled with the `scoref64`
+/// feature. The larger the number, the more relevant the document is to the search query.
+#[cfg(feature = "scoref64")]
+pub type Score = f64;
+
 /// A Score that represents the relevance of the document to the query
 ///
 /// This is modelled internally as a `f32`. The larger the number, the more relevant
 /// the document to the search query.
+#[cfg(not(feature = "scoref64"))]
 pub type Score = f32;
 
 /// A `SegmentLocalId` identifies a segment.
@@ -277,7 +284,7 @@ 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)]
@@ -289,6 +296,7 @@ mod tests {
     use crate::schema::*;
     use crate::DocAddress;
     use crate::Index;
+    use crate::IndexWriter;
     use crate::Postings;
     use crate::ReloadPolicy;
     use rand::distributions::Bernoulli;
@@ -353,14 +361,14 @@ 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);
@@ -375,76 +383,100 @@ 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()?;
-        index_writer.add_document(doc!(text_field=>"a b c"));
-        index_writer.commit()?;
-        index_writer.add_document(doc!(text_field=>"a"));
-        index_writer.add_document(doc!(text_field=>"a a"));
-        index_writer.commit()?;
-        index_writer.add_document(doc!(text_field=>"c"));
-        index_writer.commit()?;
-        let reader = index.reader()?;
-        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);
-        Ok(())
+        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().unwrap();
+        }
+        {
+            index_writer.add_document(doc!(text_field=>"a"));
+            index_writer.add_document(doc!(text_field=>"a a"));
+            index_writer.commit().unwrap();
+        }
+        {
+            index_writer.add_document(doc!(text_field=>"c"));
+            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)?;
-            assert_eq!(fieldnorm_reader.fieldnorm(0), 3);
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            {
+                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)?;
-            assert_eq!(fieldnorm_reader.fieldnorm_id(0), 0);
+            let index_reader = index.reader().unwrap();
+            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"));
-        index_writer.add_document(doc!());
-        index_writer.add_document(doc!(text_field=>"a b"));
-        index_writer.commit()?;
-        let reader = index.reader()?;
-        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);
-        Ok(())
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            {
+                let doc = doc!(text_field=>"a b c");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!();
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field=>"a b");
+                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 {
@@ -459,7 +491,7 @@ mod tests {
     }
 
     #[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 +507,7 @@ 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 +523,19 @@ 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 +543,7 @@ 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 +554,25 @@ 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 +580,7 @@ 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 +591,30 @@ 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 +624,101 @@ 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()?;
-        let reader = index.reader()?;
+        index_writer.commit().unwrap();
+        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())?
-            .read_postings(&term, IndexRecordOption::Basic)?
+            .inverted_index(term.field())
+            .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
         assert_eq!(postings.doc(), 0);
         assert_eq!(postings.advance(), TERMINATED);
-        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()?;
-        let reader = index.reader()?;
+        index_writer.commit().unwrap();
+        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())?
-            .read_postings(&term, IndexRecordOption::Basic)?
+            .inverted_index(term.field())
+            .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
         assert_eq!(postings.doc(), 0);
         assert_eq!(postings.advance(), TERMINATED);
-        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()?;
-        let reader = index.reader()?;
+        index_writer.commit().unwrap();
+        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())?
-            .read_postings(&term, IndexRecordOption::Basic)?
+            .inverted_index(term.field())
+            .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
         assert_eq!(postings.doc(), 0);
         assert_eq!(postings.advance(), TERMINATED);
-        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)?;
-        assert_eq!(inverted_index.terms().num_terms(), 0);
-        Ok(())
+        segment_reader.inverted_index(absent_field); //< should not panic
     }
 
     #[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 +726,125 @@ 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()?;
-        index_writer.add_document(doc!(text_field=>"63"));
-        index_writer.add_document(doc!(text_field=>"70"));
-        index_writer.add_document(doc!(text_field=>"34"));
-        index_writer.add_document(doc!(text_field=>"1"));
-        index_writer.add_document(doc!(text_field=>"38"));
-        index_writer.add_document(doc!(text_field=>"33"));
-        index_writer.add_document(doc!(text_field=>"40"));
-        index_writer.add_document(doc!(text_field=>"17"));
-        index_writer.delete_term(Term::from_field_text(text_field, "38"));
-        index_writer.delete_term(Term::from_field_text(text_field, "34"));
-        index_writer.commit()?;
-        reader.reload()?;
-        assert_eq!(reader.searcher().num_docs(), 6);
-        Ok(())
+        let mut index_writer = index.writer_with_num_threads(2, 6_000_000).unwrap();
+
+        let add_document = |index_writer: &mut IndexWriter, val: &'static str| {
+            let doc = doc!(text_field=>val);
+            index_writer.add_document(doc);
+        };
+
+        let remove_document = |index_writer: &mut IndexWriter, val: &'static str| {
+            let delterm = Term::from_field_text(text_field, val);
+            index_writer.delete_term(delterm);
+        };
+
+        add_document(&mut index_writer, "63");
+        add_document(&mut index_writer, "70");
+        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()?;
-            index_writer.add_document(doc!(text_field=>"af af af bc bc"));
-            index_writer.commit()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            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_eq!(postings.doc(), 0);
             assert_eq!(postings.term_freq(), 3);
             assert_eq!(postings.advance(), TERMINATED);
         }
-        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()?;
-        // writing the segment
-        let mut index_writer = index.writer_for_tests()?;
-        index_writer.add_document(doc!(text_field=>"af af af b"));
-        index_writer.add_document(doc!(text_field=>"a b c"));
-        index_writer.add_document(doc!(text_field=>"a b c d"));
-        index_writer.commit()?;
-
-        reader.reload()?;
-        let searcher = reader.searcher();
-        let get_doc_ids = |terms: Vec<Term>| {
-            let query = BooleanQuery::new_multiterms_query(terms);
-            searcher
-                .search(&query, &TEST_COLLECTOR_WITH_SCORE)
-                .map(|topdocs| topdocs.docs().to_vec())
-        };
-        assert_eq!(
-            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")])?,
-            vec![DocAddress(0, 0)]
-        );
-        assert_eq!(
-            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")])?,
-            vec![DocAddress(0, 1), DocAddress(0, 2)]
-        );
-        assert_eq!(
-            get_doc_ids(vec![Term::from_field_text(text_field, "d")])?,
-            vec![DocAddress(0, 2)]
-        );
-        assert_eq!(
-            get_doc_ids(vec![
-                Term::from_field_text(text_field, "b"),
-                Term::from_field_text(text_field, "a"),
-            ])?,
-            vec![DocAddress(0, 0), DocAddress(0, 1), DocAddress(0, 2)]
-        );
-        Ok(())
+        let reader = index.reader().unwrap();
+        {
+            // writing the segment
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            index_writer.add_document(doc!(text_field=>"af af af b"));
+            index_writer.add_document(doc!(text_field=>"a b c"));
+            index_writer.add_document(doc!(text_field=>"a b c d"));
+            index_writer.commit().unwrap();
+        }
+        {
+            reader.reload().unwrap();
+            let searcher = reader.searcher();
+            let get_doc_ids = |terms: Vec<Term>| {
+                let query = BooleanQuery::new_multiterms_query(terms);
+                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")]),
+                vec![DocAddress(0, 1), DocAddress(0, 2)]
+            );
+            assert_eq!(
+                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")]),
+                vec![DocAddress(0, 0), DocAddress(0, 1), DocAddress(0, 2)]
+            );
+            assert_eq!(
+                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")]),
+                vec![DocAddress(0, 2)]
+            );
+            assert_eq!(
+                get_doc_ids(vec![
+                    Term::from_field_text(text_field, "b"),
+                    Term::from_field_text(text_field, "a"),
+                ]),
+                vec![DocAddress(0, 0), DocAddress(0, 1), DocAddress(0, 2)]
+            );
+        }
     }
 
     #[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 +852,19 @@ 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()?;
-        index_writer.add_document(doc!(text_field=>"af b"));
-        index_writer.add_document(doc!(text_field=>"a b c"));
-        index_writer.add_document(doc!(text_field=>"a b c d"));
-        index_writer.commit()?;
-        reader.reload()?;
+        {
+            // writing the segment
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            index_writer.add_document(doc!(text_field=>"af b"));
+            index_writer.add_document(doc!(text_field=>"a b c"));
+            index_writer.add_document(doc!(text_field=>"a b c d"));
+            index_writer.commit().unwrap();
+        }
+        reader.reload().unwrap();
         assert_eq!(reader.searcher().num_docs(), 3u64);
-        Ok(())
     }
 
     #[test]
@@ -835,17 +876,17 @@ 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 +896,14 @@ 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 +942,11 @@ 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 +960,17 @@ 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 +981,12 @@ 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_reader.reload()?;
-            index_writer.add_document(doc!(id =>  doc_id));
-            index_writer.commit()?;
-            index_reader.reload()?;
+            index_writer.commit().unwrap();
+            index_reader.reload().unwrap();
+            let doc = doc!(id =>  doc_id);
+            index_writer.add_document(doc);
+            index_writer.commit().unwrap();
+            index_reader.reload().unwrap();
             let searcher = index_reader.searcher();
             // The number of document should be stable.
             assert_eq!(
@@ -954,7 +995,7 @@ mod tests {
             );
         }
 
-        index_reader.reload()?;
+        index_reader.reload().unwrap();
         let searcher = index_reader.searcher();
         let segment_ids: Vec<SegmentId> = searcher
             .segment_readers()
@@ -963,18 +1004,12 @@ 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]
-    fn test_validate_checksum() -> crate::Result<()> {
-        let index_path = tempfile::tempdir().expect("dir");
-        let schema = Schema::builder().build();
-        let index = Index::create_in_dir(&index_path, schema)?;
-        assert!(index.validate_checksum()?.is_empty());
-        Ok(())
+        assert_eq!(
+            searcher.search(&AllQuery, &Count).unwrap(),
+            DOC_COUNT as usize
+        );
     }
 }

src/positions/mod.rs

@@ -38,11 +38,11 @@ const LONG_SKIP_INTERVAL: u64 = (LONG_SKIP_IN_BLOCKS * COMPRESSION_BLOCK_SIZE) a
 pub mod tests {
 
     use super::PositionSerializer;
+    use crate::directory::ReadOnlySource;
     use crate::positions::reader::PositionReader;
-    use crate::{common::HasLen, directory::FileSlice};
     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]
@@ -62,7 +65,7 @@ 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[..]);
@@ -78,7 +81,7 @@ 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 &offset in &[1u64, 10u64, 127u64, 128u64, 130u64, 312u64] {
             for &len in &[1, 10, 130, 500] {
                 let mut v = vec![0u32; len];
@@ -97,7 +100,7 @@ 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;
 
@@ -119,7 +122,7 @@ pub mod tests {
         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 position_reader = PositionReader::new(stream.clone(), skip.clone(), 0);
         let mut buf = [0u32; 256];
         position_reader.read(128, &mut buf);
         for i in 0..256 {
@@ -139,8 +142,7 @@ pub mod tests {
         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();
+        let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), 200_000);
         position_reader.read(230, &mut buf);
         position_reader.read(9, &mut buf);
     }
@@ -155,7 +157,7 @@ pub mod tests {
         }
         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 position_reader = PositionReader::new(stream.clone(), skip.clone(), 0);
         let mut offset = 0;
         for i in 1..24 {
             buf.resize(i, 0);
@@ -173,7 +175,7 @@ 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);
         assert_eq!(buf[0], CONST_VAL);
@@ -192,8 +194,7 @@ pub mod tests {
             128 * 1024 + 7,
             128 * 10 * 1024 + 10,
         ] {
-            let mut position_reader =
-                PositionReader::new(stream.clone(), skip.clone(), offset).unwrap();
+            let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), offset);
             let mut buf = [0u32; 1];
             position_reader.read(0, &mut buf);
             assert_eq!(buf[0], offset as u32);

src/positions/reader.rs

@@ -1,13 +1,8 @@
-use std::io;
-
 use crate::common::{BinarySerializable, FixedSize};
-use crate::directory::FileSlice;
-use crate::directory::OwnedBytes;
+use crate::directory::ReadOnlySource;
 use crate::positions::COMPRESSION_BLOCK_SIZE;
 use crate::positions::LONG_SKIP_INTERVAL;
 use crate::positions::LONG_SKIP_IN_BLOCKS;
-use bitpacking::{BitPacker, BitPacker4x};
-
 /// Positions works as a long sequence of compressed block.
 /// All terms are chained one after the other.
 ///
@@ -28,28 +23,28 @@ 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,
-    position_file: FileSlice,
-    long_skip_data: OwnedBytes,
+    skip_source: ReadOnlySource,
+    position_source: ReadOnlySource,
+    long_skip_source: ReadOnlySource,
 }
 
 impl Positions {
-    pub fn new(position_file: FileSlice, skip_file: FileSlice) -> io::Result<Positions> {
-        let (body, footer) = skip_file.split_from_end(u32::SIZE_IN_BYTES);
-        let footer_data = footer.read_bytes()?;
-        let num_long_skips = u32::deserialize(&mut footer_data.as_slice())?;
-        let (skip_file, long_skip_file) =
+    pub fn new(position_source: ReadOnlySource, skip_source: ReadOnlySource) -> Positions {
+        let (body, footer) = skip_source.split_from_end(u32::SIZE_IN_BYTES);
+        let num_long_skips = u32::deserialize(&mut footer.as_slice()).expect("Index corrupted");
+        let (skip_source, long_skip_source) =
             body.split_from_end(u64::SIZE_IN_BYTES * (num_long_skips as usize));
-        let long_skip_data = long_skip_file.read_bytes()?;
-        Ok(Positions {
+        Positions {
             bit_packer: BitPacker4x::new(),
-            skip_file,
-            long_skip_data,
-            position_file,
-        })
+            skip_source,
+            long_skip_source,
+            position_source,
+        }
     }
 
     /// Returns the offset of the block associated to the given `long_skip_id`.
@@ -59,23 +54,19 @@ 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 offset_num_bytes: u64 = self.long_skip(long_skip_id);
-        let position_read = self
-            .position_file
-            .slice_from(offset_num_bytes as usize)
-            .read_bytes()?;
-        let skip_read = self
-            .skip_file
-            .slice_from(long_skip_id * LONG_SKIP_IN_BLOCKS)
-            .read_bytes()?;
-        Ok(PositionReader {
+        let mut position_read = OwnedRead::new(self.position_source.clone());
+        position_read.advance(offset_num_bytes as usize);
+        let mut skip_read = OwnedRead::new(self.skip_source.clone());
+        skip_read.advance(long_skip_id * LONG_SKIP_IN_BLOCKS);
+        PositionReader {
             bit_packer: self.bit_packer,
             skip_read,
             position_read,
@@ -83,14 +74,14 @@ impl Positions {
             block_offset: std::i64::MAX as u64,
             anchor_offset: (long_skip_id as u64) * LONG_SKIP_INTERVAL,
             abs_offset: offset,
-        })
+        }
     }
 }
 
 #[derive(Clone)]
 pub struct PositionReader {
-    skip_read: OwnedBytes,
-    position_read: OwnedBytes,
+    skip_read: OwnedRead,
+    position_read: OwnedRead,
     bit_packer: BitPacker4x,
     buffer: Box<[u32; COMPRESSION_BLOCK_SIZE]>,
 
@@ -102,12 +93,11 @@ pub struct PositionReader {
 
 impl PositionReader {
     pub fn new(
-        position_file: FileSlice,
-        skip_file: FileSlice,
+        position_source: ReadOnlySource,
+        skip_source: ReadOnlySource,
         offset: u64,
-    ) -> io::Result<PositionReader> {
-        let positions = Positions::new(position_file, skip_file)?;
-        positions.reader(offset)
+    ) -> PositionReader {
+        Positions::new(position_source, skip_source).reader(offset)
     }
 
     fn advance_num_blocks(&mut self, num_blocks: usize) {
@@ -132,7 +122,7 @@ impl PositionReader {
             "offset arguments should be increasing."
         );
         let delta_to_block_offset = offset as i64 - self.block_offset as i64;
-        if !(0..128).contains(&delta_to_block_offset) {
+        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;
@@ -141,7 +131,7 @@ impl PositionReader {
             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];
+            let num_bits = self.skip_read.get(0);
             self.bit_packer
                 .decompress(self.position_read.as_ref(), self.buffer.as_mut(), num_bits);
         } else {
@@ -151,7 +141,7 @@ impl PositionReader {
             self.anchor_offset = self.block_offset;
         }
 
-        let mut num_bits = self.skip_read.as_slice()[0];
+        let mut num_bits = self.skip_read.get(0);
         let mut position_data = self.position_read.as_ref();
 
         for i in 1.. {
@@ -165,7 +155,7 @@ impl PositionReader {
             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];
+            num_bits = self.skip_read.get(i);
             self.bit_packer
                 .decompress(position_data, self.buffer.as_mut(), num_bits);
             self.block_offset += COMPRESSION_BLOCK_SIZE as u64;

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.write_skip_index.flush()?;
+        (self.long_skips.len() as u32).serialize(&mut self.write_skiplist)?;
+        self.write_skiplist.flush()?;
         self.write_stream.flush()?;
         Ok(())
     }

src/postings/block_search.rs

@@ -109,9 +109,9 @@ impl BlockSearcher {
     /// The results should be equivalent to
     /// ```compile_fail
     /// block[..]
-    ///       .iter()
-    ///       .take_while(|&&val| val < target)
-    ///       .count()
+    //       .iter()
+    //       .take_while(|&&val| val < target)
+    //       .count()
     /// ```
     ///
     /// The `start` argument is just used to hint that the response is

src/postings/block_segment_postings.rs

@@ -1,8 +1,5 @@
-use std::io;
-
 use crate::common::{BinarySerializable, VInt};
-use crate::directory::FileSlice;
-use crate::directory::OwnedBytes;
+use crate::directory::ReadOnlySource;
 use crate::fieldnorm::FieldNormReader;
 use crate::postings::compression::{
     AlignedBuffer, BlockDecoder, VIntDecoder, COMPRESSION_BLOCK_SIZE,
@@ -37,7 +34,7 @@ pub struct BlockSegmentPostings {
 
     doc_freq: u32,
 
-    data: OwnedBytes,
+    data: ReadOnlySource,
     pub(crate) skip_reader: SkipReader,
 }
 
@@ -75,34 +72,37 @@ fn decode_vint_block(
 
 fn split_into_skips_and_postings(
     doc_freq: u32,
-    mut bytes: OwnedBytes,
-) -> (Option<OwnedBytes>, OwnedBytes) {
+    data: ReadOnlySource,
+) -> (Option<ReadOnlySource>, ReadOnlySource) {
     if doc_freq < COMPRESSION_BLOCK_SIZE as u32 {
-        return (None, bytes);
+        return (None, data);
     }
-    let skip_len = VInt::deserialize(&mut bytes).expect("Data corrupted").0 as usize;
-    let (skip_data, postings_data) = bytes.split(skip_len);
+    let mut data_byte_arr = data.as_slice();
+    let skip_len = VInt::deserialize(&mut data_byte_arr)
+        .expect("Data corrupted")
+        .0 as usize;
+    let vint_len = data.len() - data_byte_arr.len();
+    let (skip_data, postings_data) = data.slice_from(vint_len).split(skip_len);
     (Some(skip_data), postings_data)
 }
 
 impl BlockSegmentPostings {
-    pub(crate) fn open(
+    pub(crate) fn from_data(
         doc_freq: u32,
-        data: FileSlice,
+        data: ReadOnlySource,
         record_option: IndexRecordOption,
         requested_option: IndexRecordOption,
-    ) -> io::Result<BlockSegmentPostings> {
+    ) -> 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_data_opt, postings_data) = split_into_skips_and_postings(doc_freq, data);
         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),
+            None => SkipReader::new(ReadOnlySource::empty(), doc_freq, record_option),
         };
 
         let mut block_segment_postings = BlockSegmentPostings {
@@ -116,7 +116,7 @@ impl BlockSegmentPostings {
             skip_reader,
         };
         block_segment_postings.load_block();
-        Ok(block_segment_postings)
+        block_segment_postings
     }
 
     /// Returns the block_max_score for the current block.
@@ -172,15 +172,15 @@ impl BlockSegmentPostings {
     // # Warning
     //
     // This does not reset the positions list.
-    pub(crate) fn reset(&mut self, doc_freq: u32, postings_data: OwnedBytes) {
+    pub(crate) fn reset(&mut self, doc_freq: u32, postings_data: ReadOnlySource) {
         let (skip_data_opt, postings_data) = split_into_skips_and_postings(doc_freq, postings_data);
-        self.data = postings_data;
+        self.data = ReadOnlySource::new(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.skip_reader.reset(ReadOnlySource::empty(), doc_freq);
         }
         self.doc_freq = doc_freq;
         self.load_block();
@@ -344,8 +344,8 @@ impl BlockSegmentPostings {
             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),
+            data: ReadOnlySource::new(vec![]),
+            skip_reader: SkipReader::new(ReadOnlySource::new(vec![]), 0, IndexRecordOption::Basic),
         }
     }
 }
@@ -455,7 +455,7 @@ mod tests {
         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 index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let mut last_doc = 0u32;
         for &doc in docs {
             for _ in last_doc..doc {
@@ -467,12 +467,10 @@ mod tests {
         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 inverted_index = segment_reader.inverted_index(int_field);
         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()
+        let term_info = inverted_index.get_term_info(&term).unwrap();
+        inverted_index.read_block_postings_from_terminfo(&term_info, IndexRecordOption::Basic)
     }
 
     #[test]
@@ -493,38 +491,37 @@ mod tests {
     }
 
     #[test]
-    fn test_reset_block_segment_postings() -> crate::Result<()> {
+    fn test_reset_block_segment_postings() {
         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()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         // 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();
+        index_writer.commit().unwrap();
+        let searcher = index.reader().unwrap().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();
+            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)?;
+                .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)?;
+            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

@@ -310,7 +310,6 @@ pub mod tests {
 mod bench {
 
     use super::*;
-    use crate::TERMINATED;
     use rand::rngs::StdRng;
     use rand::Rng;
     use rand::SeedableRng;
@@ -341,7 +340,7 @@ 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 +375,9 @@ 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);
         });
     }
 }

src/postings/mod.rs

@@ -15,15 +15,21 @@ mod stacker;
 mod term_info;
 
 pub(crate) use self::block_search::BlockSearcher;
-pub use self::block_segment_postings::BlockSegmentPostings;
-pub use self::postings::Postings;
+
 pub(crate) use self::postings_writer::MultiFieldPostingsWriter;
-pub use self::segment_postings::SegmentPostings;
 pub use self::serializer::{FieldSerializer, InvertedIndexSerializer};
+
+pub use self::postings::Postings;
 pub(crate) use self::skip::{BlockInfo, SkipReader};
-pub(crate) use self::stacker::compute_table_size;
 pub use self::term_info::TermInfo;
 
+pub use self::block_segment_postings::BlockSegmentPostings;
+pub use self::segment_postings::SegmentPostings;
+
+pub(crate) use self::stacker::compute_table_size;
+
+pub use crate::common::HasLen;
+
 pub(crate) type UnorderedTermId = u64;
 
 #[cfg_attr(feature = "cargo-clippy", allow(clippy::enum_variant_names))]
@@ -36,8 +42,8 @@ pub(crate) enum FreqReadingOption {
 
 #[cfg(test)]
 pub mod tests {
-    use super::InvertedIndexSerializer;
-    use super::Postings;
+
+    use super::*;
     use crate::core::Index;
     use crate::core::SegmentComponent;
     use crate::core::SegmentReader;
@@ -47,14 +53,16 @@ pub mod tests {
     use crate::indexer::SegmentWriter;
     use crate::merge_policy::NoMergePolicy;
     use crate::query::Scorer;
+    use crate::schema::{Document, Schema, Term, INDEXED, STRING, TEXT};
     use crate::schema::{Field, TextOptions};
     use crate::schema::{IndexRecordOption, TextFieldIndexing};
-    use crate::schema::{Schema, Term, INDEXED, TEXT};
     use crate::tokenizer::{SimpleTokenizer, MAX_TOKEN_LEN};
     use crate::DocId;
-    use crate::HasLen;
     use crate::Score;
-    use std::{iter, mem};
+    use once_cell::sync::Lazy;
+    use rand::rngs::StdRng;
+    use rand::{Rng, SeedableRng};
+    use std::iter;
 
     #[test]
     pub fn test_position_write() -> crate::Result<()> {
@@ -71,7 +79,6 @@ pub mod tests {
             field_serializer.write_doc(doc_id, 4, &delta_positions)?;
         }
         field_serializer.close_term()?;
-        mem::drop(field_serializer);
         posting_serializer.close()?;
         let read = segment.open_read(SegmentComponent::POSITIONS)?;
         assert!(read.len() <= 140);
@@ -84,7 +91,7 @@ pub mod tests {
         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_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 30_000_000)?;
         index_writer.add_document(doc!(title => r#"abc abc abc"#));
         index_writer.add_document(doc!(title => r#"abc be be be be abc"#));
         for _ in 0..1_000 {
@@ -94,12 +101,12 @@ pub mod tests {
         index_writer.commit()?;
 
         let searcher = index.reader()?.searcher();
-        let inverted_index = searcher.segment_reader(0u32).inverted_index(title)?;
+        let inverted_index = searcher.segment_reader(0u32).inverted_index(title);
         let term = Term::from_field_text(title, "abc");
         let mut positions = Vec::new();
         {
             let mut postings = inverted_index
-                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
             assert_eq!(postings.doc(), 0);
             postings.positions(&mut positions);
@@ -113,7 +120,7 @@ pub mod tests {
         }
         {
             let mut postings = inverted_index
-                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
             assert_eq!(postings.doc(), 0);
             assert_eq!(postings.advance(), 1);
@@ -122,7 +129,7 @@ pub mod tests {
         }
         {
             let mut postings = inverted_index
-                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
             assert_eq!(postings.seek(1), 1);
             assert_eq!(postings.doc(), 1);
@@ -131,7 +138,7 @@ pub mod tests {
         }
         {
             let mut postings = inverted_index
-                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
             assert_eq!(postings.seek(1002), 1002);
             assert_eq!(postings.doc(), 1002);
@@ -140,7 +147,7 @@ pub mod tests {
         }
         {
             let mut postings = inverted_index
-                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)?
+                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
             assert_eq!(postings.seek(100), 100);
             assert_eq!(postings.seek(1002), 1002);
@@ -152,7 +159,7 @@ pub mod tests {
     }
 
     #[test]
-    pub fn test_drop_token_that_are_too_long() -> crate::Result<()> {
+    pub fn test_drop_token_that_are_too_long() {
         let ok_token_text: String = iter::repeat('A').take(MAX_TOKEN_LEN).collect();
         let mut exceeding_token_text: String = iter::repeat('A').take(MAX_TOKEN_LEN + 1).collect();
         exceeding_token_text.push_str(" hello");
@@ -169,7 +176,7 @@ pub mod tests {
             .tokenizers()
             .register("simple_no_truncation", SimpleTokenizer);
         let reader = index.reader().unwrap();
-        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!(text_field=>exceeding_token_text));
@@ -177,10 +184,10 @@ pub mod tests {
             reader.reload().unwrap();
             let searcher = reader.searcher();
             let segment_reader = searcher.segment_reader(0u32);
-            let inverted_index = segment_reader.inverted_index(text_field)?;
+            let inverted_index = segment_reader.inverted_index(text_field);
             assert_eq!(inverted_index.terms().num_terms(), 1);
             let mut bytes = vec![];
-            assert!(inverted_index.terms().ord_to_term(0, &mut bytes)?);
+            assert!(inverted_index.terms().ord_to_term(0, &mut bytes));
             assert_eq!(&bytes, b"hello");
         }
         {
@@ -189,17 +196,16 @@ pub mod tests {
             reader.reload().unwrap();
             let searcher = reader.searcher();
             let segment_reader = searcher.segment_reader(1u32);
-            let inverted_index = segment_reader.inverted_index(text_field)?;
+            let inverted_index = segment_reader.inverted_index(text_field);
             assert_eq!(inverted_index.terms().num_terms(), 1);
             let mut bytes = vec![];
-            assert!(inverted_index.terms().ord_to_term(0, &mut bytes)?);
+            assert!(inverted_index.terms().ord_to_term(0, &mut bytes));
             assert_eq!(&bytes[..], ok_token_text.as_bytes());
         }
-        Ok(())
     }
 
     #[test]
-    pub fn test_position_and_fieldnorm1() -> crate::Result<()> {
+    pub fn test_position_and_fieldnorm1() {
         let mut positions = Vec::new();
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
@@ -211,38 +217,42 @@ pub mod tests {
             let mut segment_writer =
                 SegmentWriter::for_segment(3_000_000, segment.clone(), &schema).unwrap();
             {
+                let mut doc = Document::default();
                 // checking that position works if the field has two values
+                doc.add_text(text_field, "a b a c a d a a.");
+                doc.add_text(text_field, "d d d d a");
                 let op = AddOperation {
                     opstamp: 0u64,
-                    document: doc!(
-                       text_field => "a b a c a d a a.",
-                       text_field => "d d d d a"
-                    ),
+                    document: doc,
                 };
-                segment_writer.add_document(op, &schema)?;
+                segment_writer.add_document(op, &schema).unwrap();
             }
             {
+                let mut doc = Document::default();
+                doc.add_text(text_field, "b a");
                 let op = AddOperation {
                     opstamp: 1u64,
-                    document: doc!(text_field => "b a"),
+                    document: doc,
                 };
                 segment_writer.add_document(op, &schema).unwrap();
             }
             for i in 2..1000 {
-                let mut text: String = iter::repeat("e ").take(i).collect();
+                let mut doc = Document::default();
+                let mut text = iter::repeat("e ").take(i).collect::<String>();
                 text.push_str(" a");
+                doc.add_text(text_field, &text);
                 let op = AddOperation {
                     opstamp: 2u64,
-                    document: doc!(text_field => text),
+                    document: doc,
                 };
                 segment_writer.add_document(op, &schema).unwrap();
             }
-            segment_writer.finalize()?;
+            segment_writer.finalize().unwrap();
         }
         {
-            let segment_reader = SegmentReader::open(&segment)?;
+            let segment_reader = SegmentReader::open(&segment).unwrap();
             {
-                let fieldnorm_reader = segment_reader.get_fieldnorms_reader(text_field)?;
+                let fieldnorm_reader = segment_reader.get_fieldnorms_reader(text_field);
                 assert_eq!(fieldnorm_reader.fieldnorm(0), 8 + 5);
                 assert_eq!(fieldnorm_reader.fieldnorm(1), 2);
                 for i in 2..1000 {
@@ -255,15 +265,15 @@ pub mod tests {
             {
                 let term_a = Term::from_field_text(text_field, "abcdef");
                 assert!(segment_reader
-                    .inverted_index(term_a.field())?
-                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)?
+                    .inverted_index(term_a.field())
+                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
                     .is_none());
             }
             {
                 let term_a = Term::from_field_text(text_field, "a");
                 let mut postings_a = segment_reader
-                    .inverted_index(term_a.field())?
-                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)?
+                    .inverted_index(term_a.field())
+                    .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert_eq!(postings_a.len(), 1000);
                 assert_eq!(postings_a.doc(), 0);
@@ -285,8 +295,8 @@ pub mod tests {
             {
                 let term_e = Term::from_field_text(text_field, "e");
                 let mut postings_e = segment_reader
-                    .inverted_index(term_e.field())?
-                    .read_postings(&term_e, IndexRecordOption::WithFreqsAndPositions)?
+                    .inverted_index(term_e.field())
+                    .read_postings(&term_e, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert_eq!(postings_e.len(), 1000 - 2);
                 for i in 2u32..1000u32 {
@@ -302,18 +312,17 @@ pub mod tests {
                 assert_eq!(postings_e.doc(), TERMINATED);
             }
         }
-        Ok(())
     }
 
     #[test]
-    pub fn test_position_and_fieldnorm2() -> crate::Result<()> {
+    pub fn test_position_and_fieldnorm2() {
         let mut positions: Vec<u32> = Vec::new();
         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 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 => "g b b d c g c"));
             index_writer.add_document(doc!(text_field => "g a b b a d c g c"));
             assert!(index_writer.commit().is_ok());
@@ -322,17 +331,16 @@ pub mod tests {
         let searcher = index.reader().unwrap().searcher();
         let segment_reader = searcher.segment_reader(0);
         let mut postings = segment_reader
-            .inverted_index(text_field)?
-            .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)?
+            .inverted_index(text_field)
+            .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
             .unwrap();
         assert_eq!(postings.doc(), 1u32);
         postings.positions(&mut positions);
         assert_eq!(&positions[..], &[1u32, 4]);
-        Ok(())
     }
 
     #[test]
-    fn test_skip_next() -> crate::Result<()> {
+    fn test_skip_next() {
         let term_0 = Term::from_field_u64(Field::from_field_id(0), 0);
         let term_1 = Term::from_field_u64(Field::from_field_id(0), 1);
         let term_2 = Term::from_field_u64(Field::from_field_id(0), 2);
@@ -343,9 +351,10 @@ pub mod tests {
             let mut schema_builder = Schema::builder();
             let value_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();
                 for i in 0u64..num_docs as u64 {
                     let doc = doc!(value_field => 2u64, value_field => i % 2u64);
                     index_writer.add_document(doc);
@@ -354,15 +363,15 @@ pub mod tests {
             }
             index
         };
-        let searcher = index.reader()?.searcher();
+        let searcher = index.reader().unwrap().searcher();
         let segment_reader = searcher.segment_reader(0);
 
         // check that the basic usage works
         for i in 0..num_docs - 1 {
             for j in i + 1..num_docs {
                 let mut segment_postings = segment_reader
-                    .inverted_index(term_2.field())?
-                    .read_postings(&term_2, IndexRecordOption::Basic)?
+                    .inverted_index(term_2.field())
+                    .read_postings(&term_2, IndexRecordOption::Basic)
                     .unwrap();
                 assert_eq!(segment_postings.seek(i), i);
                 assert_eq!(segment_postings.doc(), i);
@@ -374,8 +383,8 @@ pub mod tests {
 
         {
             let mut segment_postings = segment_reader
-                .inverted_index(term_2.field())?
-                .read_postings(&term_2, IndexRecordOption::Basic)?
+                .inverted_index(term_2.field())
+                .read_postings(&term_2, IndexRecordOption::Basic)
                 .unwrap();
 
             // check that `skip_next` advances the iterator
@@ -394,8 +403,8 @@ pub mod tests {
         // check that filtering works
         {
             let mut segment_postings = segment_reader
-                .inverted_index(term_0.field())?
-                .read_postings(&term_0, IndexRecordOption::Basic)?
+                .inverted_index(term_0.field())
+                .read_postings(&term_0, IndexRecordOption::Basic)
                 .unwrap();
 
             for i in 0..num_docs / 2 {
@@ -404,8 +413,8 @@ pub mod tests {
             }
 
             let mut segment_postings = segment_reader
-                .inverted_index(term_0.field())?
-                .read_postings(&term_0, IndexRecordOption::Basic)?
+                .inverted_index(term_0.field())
+                .read_postings(&term_0, IndexRecordOption::Basic)
                 .unwrap();
 
             for i in 0..num_docs / 2 - 1 {
@@ -416,19 +425,19 @@ pub mod tests {
 
         // delete some of the documents
         {
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.delete_term(term_0);
             assert!(index_writer.commit().is_ok());
         }
-        let searcher = index.reader()?.searcher();
+        let searcher = index.reader().unwrap().searcher();
         assert_eq!(searcher.segment_readers().len(), 1);
         let segment_reader = searcher.segment_reader(0);
 
         // make sure seeking still works
         for i in 0..num_docs {
             let mut segment_postings = segment_reader
-                .inverted_index(term_2.field())?
-                .read_postings(&term_2, IndexRecordOption::Basic)?
+                .inverted_index(term_2.field())
+                .read_postings(&term_2, IndexRecordOption::Basic)
                 .unwrap();
 
             if i % 2 == 0 {
@@ -444,8 +453,8 @@ pub mod tests {
         // now try with a longer sequence
         {
             let mut segment_postings = segment_reader
-                .inverted_index(term_2.field())?
-                .read_postings(&term_2, IndexRecordOption::Basic)?
+                .inverted_index(term_2.field())
+                .read_postings(&term_2, IndexRecordOption::Basic)
                 .unwrap();
 
             let mut last = 2; // start from 5 to avoid seeking to 3 twice
@@ -470,21 +479,69 @@ pub mod tests {
 
         // delete everything else
         {
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.delete_term(term_1);
             assert!(index_writer.commit().is_ok());
         }
-        let searcher = index.reader()?.searcher();
+        let searcher = index.reader().unwrap().searcher();
 
         // finally, check that it's empty
         {
-            let searchable_segment_ids = index.searchable_segment_ids()?;
+            let searchable_segment_ids = index
+                .searchable_segment_ids()
+                .expect("could not get index segment ids");
             assert!(searchable_segment_ids.is_empty());
             assert_eq!(searcher.num_docs(), 0);
         }
-        Ok(())
     }
 
+    pub static TERM_A: Lazy<Term> = Lazy::new(|| {
+        let field = Field::from_field_id(0);
+        Term::from_field_text(field, "a")
+    });
+    pub static TERM_B: Lazy<Term> = Lazy::new(|| {
+        let field = Field::from_field_id(0);
+        Term::from_field_text(field, "b")
+    });
+    pub static TERM_C: Lazy<Term> = Lazy::new(|| {
+        let field = Field::from_field_id(0);
+        Term::from_field_text(field, "c")
+    });
+    pub static TERM_D: Lazy<Term> = Lazy::new(|| {
+        let field = Field::from_field_id(0);
+        Term::from_field_text(field, "d")
+    });
+
+    pub static INDEX: Lazy<Index> = Lazy::new(|| {
+        let mut schema_builder = Schema::builder();
+        let text_field = schema_builder.add_text_field("text", STRING);
+        let schema = schema_builder.build();
+
+        let mut rng: StdRng = StdRng::from_seed([1u8; 32]);
+
+        let index = Index::create_in_ram(schema);
+        let posting_list_size = 1_000_000;
+        {
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            for _ in 0..posting_list_size {
+                let mut doc = Document::default();
+                if rng.gen_bool(1f64 / 15f64) {
+                    doc.add_text(text_field, "a");
+                }
+                if rng.gen_bool(1f64 / 10f64) {
+                    doc.add_text(text_field, "b");
+                }
+                if rng.gen_bool(1f64 / 5f64) {
+                    doc.add_text(text_field, "c");
+                }
+                doc.add_text(text_field, "d");
+                index_writer.add_document(doc);
+            }
+            assert!(index_writer.commit().is_ok());
+        }
+        index
+    });
+
     /// Wraps a given docset, and forward alls call but the
     /// `.skip_next(...)`. This is useful to test that a specialized
     /// implementation of `.skip_next(...)` is consistent
@@ -549,65 +606,15 @@ pub mod tests {
 
 #[cfg(all(test, feature = "unstable"))]
 mod bench {
+
+    use super::tests::*;
     use crate::docset::TERMINATED;
     use crate::query::Intersection;
     use crate::schema::IndexRecordOption;
-    use crate::schema::{Document, Field, Schema, Term, STRING};
     use crate::tests;
     use crate::DocSet;
-    use crate::Index;
-    use once_cell::sync::Lazy;
-    use rand::rngs::StdRng;
-    use rand::{Rng, SeedableRng};
     use test::{self, Bencher};
 
-    pub static TERM_A: Lazy<Term> = Lazy::new(|| {
-        let field = Field::from_field_id(0);
-        Term::from_field_text(field, "a")
-    });
-    pub static TERM_B: Lazy<Term> = Lazy::new(|| {
-        let field = Field::from_field_id(0);
-        Term::from_field_text(field, "b")
-    });
-    pub static TERM_C: Lazy<Term> = Lazy::new(|| {
-        let field = Field::from_field_id(0);
-        Term::from_field_text(field, "c")
-    });
-    pub static TERM_D: Lazy<Term> = Lazy::new(|| {
-        let field = Field::from_field_id(0);
-        Term::from_field_text(field, "d")
-    });
-
-    pub static INDEX: Lazy<Index> = Lazy::new(|| {
-        let mut schema_builder = Schema::builder();
-        let text_field = schema_builder.add_text_field("text", STRING);
-        let schema = schema_builder.build();
-
-        let mut rng: StdRng = StdRng::from_seed([1u8; 32]);
-
-        let index = Index::create_in_ram(schema);
-        let posting_list_size = 1_000_000;
-        {
-            let mut index_writer = index.writer_for_tests().unwrap();
-            for _ in 0..posting_list_size {
-                let mut doc = Document::default();
-                if rng.gen_bool(1f64 / 15f64) {
-                    doc.add_text(text_field, "a");
-                }
-                if rng.gen_bool(1f64 / 10f64) {
-                    doc.add_text(text_field, "b");
-                }
-                if rng.gen_bool(1f64 / 5f64) {
-                    doc.add_text(text_field, "c");
-                }
-                doc.add_text(text_field, "d");
-                index_writer.add_document(doc);
-            }
-            assert!(index_writer.commit().is_ok());
-        }
-        index
-    });
-
     #[bench]
     fn bench_segment_postings(b: &mut Bencher) {
         let reader = INDEX.reader().unwrap();
@@ -617,9 +624,7 @@ mod bench {
         b.iter(|| {
             let mut segment_postings = segment_reader
                 .inverted_index(TERM_A.field())
-                .unwrap()
                 .read_postings(&*TERM_A, IndexRecordOption::Basic)
-                .unwrap()
                 .unwrap();
             while segment_postings.advance() != TERMINATED {}
         });
@@ -633,27 +638,19 @@ mod bench {
         b.iter(|| {
             let segment_postings_a = segment_reader
                 .inverted_index(TERM_A.field())
-                .unwrap()
                 .read_postings(&*TERM_A, IndexRecordOption::Basic)
-                .unwrap()
                 .unwrap();
             let segment_postings_b = segment_reader
                 .inverted_index(TERM_B.field())
-                .unwrap()
                 .read_postings(&*TERM_B, IndexRecordOption::Basic)
-                .unwrap()
                 .unwrap();
             let segment_postings_c = segment_reader
                 .inverted_index(TERM_C.field())
-                .unwrap()
                 .read_postings(&*TERM_C, IndexRecordOption::Basic)
-                .unwrap()
                 .unwrap();
             let segment_postings_d = segment_reader
                 .inverted_index(TERM_D.field())
-                .unwrap()
                 .read_postings(&*TERM_D, IndexRecordOption::Basic)
-                .unwrap()
                 .unwrap();
             let mut intersection = Intersection::new(vec![
                 segment_postings_a,
@@ -673,9 +670,7 @@ mod bench {
 
         let mut segment_postings = segment_reader
             .inverted_index(TERM_A.field())
-            .unwrap()
             .read_postings(&*TERM_A, IndexRecordOption::Basic)
-            .unwrap()
             .unwrap();
 
         let mut existing_docs = Vec::new();
@@ -691,9 +686,7 @@ mod bench {
         b.iter(|| {
             let mut segment_postings = segment_reader
                 .inverted_index(TERM_A.field())
-                .unwrap()
                 .read_postings(&*TERM_A, IndexRecordOption::Basic)
-                .unwrap()
                 .unwrap();
             for doc in &existing_docs {
                 if segment_postings.seek(*doc) == TERMINATED {
@@ -732,14 +725,12 @@ mod bench {
             let n: u32 = test::black_box(17);
             let mut segment_postings = segment_reader
                 .inverted_index(TERM_A.field())
-                .unwrap()
                 .read_postings(&*TERM_A, IndexRecordOption::Basic)
-                .unwrap()
                 .unwrap();
             let mut s = 0u32;
             while segment_postings.doc() != TERMINATED {
                 s += (segment_postings.doc() & n) % 1024;
-                segment_postings.advance();
+                segment_postings.advance()
             }
             s
         });

src/postings/postings_writer.rs

@@ -9,6 +9,7 @@ use crate::postings::{FieldSerializer, InvertedIndexSerializer};
 use crate::schema::IndexRecordOption;
 use crate::schema::{Field, FieldEntry, FieldType, Schema, Term};
 use crate::termdict::TermOrdinal;
+use crate::tokenizer::TokenStream;
 use crate::tokenizer::{Token, MAX_TOKEN_LEN};
 use crate::DocId;
 use fnv::FnvHashMap;
@@ -37,8 +38,12 @@ fn posting_from_field_entry(field_entry: &FieldEntry) -> Box<dyn PostingsWriter>
         | FieldType::I64(_)
         | FieldType::F64(_)
         | FieldType::Date(_)
-        | FieldType::Bytes(_)
         | FieldType::HierarchicalFacet => SpecializedPostingsWriter::<NothingRecorder>::new_boxed(),
+        FieldType::Bytes => {
+            // FieldType::Bytes cannot actually be indexed.
+            // TODO fix during the indexer refactoring described in #276
+            SpecializedPostingsWriter::<NothingRecorder>::new_boxed()
+        }
     }
 }
 
@@ -99,16 +104,16 @@ impl MultiFieldPostingsWriter {
         &mut self,
         doc: DocId,
         field: Field,
-        token_stream: &mut dyn Iterator<Item = Token>,
-        term_buffer: &mut Term,
+        token_stream: &mut dyn TokenStream,
     ) -> u32 {
-        self.per_field_postings_writers[field.field_id() as usize].index_text(
+        let postings_writer =
+            self.per_field_postings_writers[field.field_id() as usize].deref_mut();
+        postings_writer.index_text(
             &mut self.term_index,
             doc,
             field,
             token_stream,
             &mut self.heap,
-            term_buffer,
         )
     }
 
@@ -154,12 +159,11 @@ impl MultiFieldPostingsWriter {
                     unordered_term_mappings.insert(field, mapping);
                 }
                 FieldType::U64(_) | FieldType::I64(_) | FieldType::F64(_) | FieldType::Date(_) => {}
-                FieldType::Bytes(_) => {}
+                FieldType::Bytes => {}
             }
 
-            let postings_writer =
-                self.per_field_postings_writers[field.field_id() as usize].as_ref();
-            let fieldnorm_reader = fieldnorm_readers.get_field(field)?;
+            let postings_writer = &self.per_field_postings_writers[field.field_id() as usize];
+            let fieldnorm_reader = fieldnorm_readers.get_field(field);
             let mut field_serializer = serializer.new_field(
                 field,
                 postings_writer.total_num_tokens(),
@@ -214,22 +218,15 @@ pub trait PostingsWriter {
         term_index: &mut TermHashMap,
         doc_id: DocId,
         field: Field,
-        token_stream: &mut dyn Iterator<Item = Token>,
+        token_stream: &mut dyn TokenStream,
         heap: &mut MemoryArena,
-        term_buffer: &mut Term,
     ) -> u32 {
-        term_buffer.set_field(field);
+        let mut term = Term::for_field(field);
         let mut sink = |token: &Token| {
             // We skip all tokens with a len greater than u16.
             if token.text.len() <= MAX_TOKEN_LEN {
-                term_buffer.set_text(token.text.as_str());
-                self.subscribe(
-                    term_index,
-                    doc_id,
-                    token.position as u32,
-                    &term_buffer,
-                    heap,
-                );
+                term.set_text(token.text.as_str());
+                self.subscribe(term_index, doc_id, token.position as u32, &term, heap);
             } else {
                 info!(
                     "A token exceeding MAX_TOKEN_LEN ({}>{}) was dropped. Search for \
@@ -239,7 +236,7 @@ pub trait PostingsWriter {
                 );
             }
         };
-        token_stream.map(|tok| sink(&tok)).count() as u32
+        token_stream.process(&mut sink)
     }
 
     fn total_num_tokens(&self) -> u64;

src/postings/segment_postings.rs

@@ -1,16 +1,21 @@
 use crate::common::HasLen;
-use crate::directory::FileSlice;
+
 use crate::docset::DocSet;
-use crate::fastfield::DeleteBitSet;
 use crate::positions::PositionReader;
+
 use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
 use crate::postings::serializer::PostingsSerializer;
 use crate::postings::BlockSearcher;
-use crate::postings::BlockSegmentPostings;
+
 use crate::postings::Postings;
+
 use crate::schema::IndexRecordOption;
 use crate::{DocId, TERMINATED};
 
+use crate::directory::ReadOnlySource;
+use crate::fastfield::DeleteBitSet;
+use crate::postings::BlockSegmentPostings;
+
 /// `SegmentPostings` represents the inverted list or postings associated to
 /// a term in a `Segment`.
 ///
@@ -72,7 +77,7 @@ impl SegmentPostings {
         let mut buffer = Vec::new();
         {
             let mut postings_serializer =
-                PostingsSerializer::new(&mut buffer, 0.0, IndexRecordOption::Basic, None);
+                PostingsSerializer::new(&mut buffer, 0.0, false, false, None);
             postings_serializer.new_term(docs.len() as u32);
             for &doc in docs {
                 postings_serializer.write_doc(doc, 1u32);
@@ -81,13 +86,12 @@ impl SegmentPostings {
                 .close_term(docs.len() as u32)
                 .expect("In memory Serialization should never fail.");
         }
-        let block_segment_postings = BlockSegmentPostings::open(
+        let block_segment_postings = BlockSegmentPostings::from_data(
             docs.len() as u32,
-            FileSlice::from(buffer),
+            ReadOnlySource::from(buffer),
             IndexRecordOption::Basic,
             IndexRecordOption::Basic,
-        )
-        .unwrap();
+        );
         SegmentPostings::from_block_postings(block_segment_postings, None)
     }
 
@@ -110,13 +114,14 @@ impl SegmentPostings {
                     .iter()
                     .map(|&fieldnorm| fieldnorm as u64)
                     .sum::<u64>();
-                total_num_tokens as Score / fieldnorms.len() as Score
+                total_num_tokens as Score / fieldnorms.len() as f32
             })
             .unwrap_or(0.0);
         let mut postings_serializer = PostingsSerializer::new(
             &mut buffer,
             average_field_norm,
-            IndexRecordOption::WithFreqs,
+            true,
+            false,
             fieldnorm_reader,
         );
         postings_serializer.new_term(doc_and_tfs.len() as u32);
@@ -126,13 +131,12 @@ impl SegmentPostings {
         postings_serializer
             .close_term(doc_and_tfs.len() as u32)
             .unwrap();
-        let block_segment_postings = BlockSegmentPostings::open(
+        let block_segment_postings = BlockSegmentPostings::from_data(
             doc_and_tfs.len() as u32,
-            FileSlice::from(buffer),
+            ReadOnlySource::from(buffer),
             IndexRecordOption::WithFreqs,
             IndexRecordOption::WithFreqs,
-        )
-        .unwrap();
+        );
         SegmentPostings::from_block_postings(block_segment_postings, None)
     }
 
@@ -200,7 +204,7 @@ impl DocSet for SegmentPostings {
     }
 
     /// Return the current document's `DocId`.
-    #[inline(always)]
+    #[inline]
     fn doc(&self) -> DocId {
         self.block_cursor.doc(self.cur)
     }

src/postings/serializer.rs

@@ -8,8 +8,8 @@ use crate::positions::PositionSerializer;
 use crate::postings::compression::{BlockEncoder, VIntEncoder, COMPRESSION_BLOCK_SIZE};
 use crate::postings::skip::SkipSerializer;
 use crate::query::BM25Weight;
+use crate::schema::Schema;
 use crate::schema::{Field, FieldEntry, FieldType};
-use crate::schema::{IndexRecordOption, Schema};
 use crate::termdict::{TermDictionaryBuilder, TermOrdinal};
 use crate::{DocId, Score};
 use std::cmp::Ordering;
@@ -143,24 +143,30 @@ impl<'a> FieldSerializer<'a> {
         fieldnorm_reader: Option<FieldNormReader>,
     ) -> io::Result<FieldSerializer<'a>> {
         total_num_tokens.serialize(postings_write)?;
-        let mode = match field_type {
+        let (term_freq_enabled, position_enabled): (bool, bool) = match field_type {
             FieldType::Str(ref text_options) => {
                 if let Some(text_indexing_options) = text_options.get_indexing_options() {
-                    text_indexing_options.index_option()
+                    let index_option = text_indexing_options.index_option();
+                    (index_option.has_freq(), index_option.has_positions())
                 } else {
-                    IndexRecordOption::Basic
+                    (false, false)
                 }
             }
-            _ => IndexRecordOption::Basic,
+            _ => (false, false),
         };
         let term_dictionary_builder = TermDictionaryBuilder::create(term_dictionary_write)?;
         let average_fieldnorm = fieldnorm_reader
             .as_ref()
             .map(|ff_reader| (total_num_tokens as Score / ff_reader.num_docs() as Score))
             .unwrap_or(0.0);
-        let postings_serializer =
-            PostingsSerializer::new(postings_write, average_fieldnorm, mode, fieldnorm_reader);
-        let positions_serializer_opt = if mode.has_positions() {
+        let postings_serializer = PostingsSerializer::new(
+            postings_write,
+            average_fieldnorm,
+            term_freq_enabled,
+            position_enabled,
+            fieldnorm_reader,
+        );
+        let positions_serializer_opt = if position_enabled {
             Some(PositionSerializer::new(positions_write, positionsidx_write))
         } else {
             None
@@ -177,16 +183,14 @@ impl<'a> FieldSerializer<'a> {
     }
 
     fn current_term_info(&self) -> TermInfo {
-        let positions_idx =
-            if let Some(positions_serializer) = self.positions_serializer_opt.as_ref() {
-                positions_serializer.positions_idx()
-            } else {
-                0u64
-            };
+        let positions_idx = self
+            .positions_serializer_opt
+            .as_ref()
+            .map(PositionSerializer::positions_idx)
+            .unwrap_or(0u64);
         TermInfo {
             doc_freq: 0,
-            postings_start_offset: self.postings_serializer.addr(),
-            postings_stop_offset: 0u64,
+            postings_offset: self.postings_serializer.addr(),
             positions_idx,
         }
     }
@@ -240,11 +244,10 @@ impl<'a> FieldSerializer<'a> {
     /// using `VInt` encoding.
     pub fn close_term(&mut self) -> io::Result<()> {
         if self.term_open {
-            self.postings_serializer
-                .close_term(self.current_term_info.doc_freq)?;
-            self.current_term_info.postings_stop_offset = self.postings_serializer.addr();
             self.term_dictionary_builder
                 .insert_value(&self.current_term_info)?;
+            self.postings_serializer
+                .close_term(self.current_term_info.doc_freq)?;
             self.term_open = false;
         }
         Ok(())
@@ -320,7 +323,8 @@ pub struct PostingsSerializer<W: Write> {
     postings_write: Vec<u8>,
     skip_write: SkipSerializer,
 
-    mode: IndexRecordOption,
+    termfreq_enabled: bool,
+    termfreq_sum_enabled: bool,
     fieldnorm_reader: Option<FieldNormReader>,
 
     bm25_weight: Option<BM25Weight>,
@@ -334,7 +338,8 @@ impl<W: Write> PostingsSerializer<W> {
     pub fn new(
         write: W,
         avg_fieldnorm: Score,
-        mode: IndexRecordOption,
+        termfreq_enabled: bool,
+        termfreq_sum_enabled: bool,
         fieldnorm_reader: Option<FieldNormReader>,
     ) -> PostingsSerializer<W> {
         let num_docs = fieldnorm_reader
@@ -351,7 +356,8 @@ impl<W: Write> PostingsSerializer<W> {
             skip_write: SkipSerializer::new(),
 
             last_doc_id_encoded: 0u32,
-            mode,
+            termfreq_enabled,
+            termfreq_sum_enabled,
 
             fieldnorm_reader,
             bm25_weight: None,
@@ -362,7 +368,7 @@ impl<W: Write> PostingsSerializer<W> {
     }
 
     pub fn new_term(&mut self, term_doc_freq: u32) {
-        if self.mode.has_freq() && self.num_docs > 0 {
+        if self.termfreq_enabled && self.num_docs > 0 {
             let bm25_weight = BM25Weight::for_one_term(
                 term_doc_freq as u64,
                 self.num_docs as u64,
@@ -384,15 +390,13 @@ impl<W: Write> PostingsSerializer<W> {
             // last el block 0, offset block 1,
             self.postings_write.extend(block_encoded);
         }
-        if self.mode.has_freq() {
+        if self.termfreq_enabled {
             let (num_bits, block_encoded): (u8, &[u8]) = self
                 .block_encoder
                 .compress_block_unsorted(&self.block.term_freqs());
             self.postings_write.extend(block_encoded);
             self.skip_write.write_term_freq(num_bits);
-            if self.mode.has_positions() {
-                // We serialize the sum of term freqs within the skip information
-                // in order to navigate through positions.
+            if self.termfreq_sum_enabled {
                 let sum_freq = self.block.term_freqs().iter().cloned().sum();
                 self.skip_write.write_total_term_freq(sum_freq);
             }
@@ -451,7 +455,7 @@ impl<W: Write> PostingsSerializer<W> {
                 self.postings_write.write_all(block_encoded)?;
             }
             // ... Idem for term frequencies
-            if self.mode.has_freq() {
+            if self.termfreq_enabled {
                 let block_encoded = self
                     .block_encoder
                     .compress_vint_unsorted(self.block.term_freqs());

src/postings/skip.rs

@@ -1,46 +1,33 @@
-use std::convert::TryInto;
-
-use crate::directory::OwnedBytes;
+use crate::common::{read_u32_vint_no_advance, serialize_vint_u32, BinarySerializable, VInt};
+use crate::directory::ReadOnlySource;
 use crate::postings::compression::{compressed_block_size, COMPRESSION_BLOCK_SIZE};
 use crate::query::BM25Weight;
 use crate::schema::IndexRecordOption;
 use crate::{DocId, Score, TERMINATED};
-
-#[inline(always)]
-fn encode_block_wand_max_tf(max_tf: u32) -> u8 {
-    max_tf.min(u8::MAX as u32) as u8
-}
-
-#[inline(always)]
-fn decode_block_wand_max_tf(max_tf_code: u8) -> u32 {
-    if max_tf_code == u8::MAX {
-        u32::MAX
-    } else {
-        max_tf_code as u32
-    }
-}
-
-#[inline(always)]
-fn read_u32(data: &[u8]) -> u32 {
-    u32::from_le_bytes(data[..4].try_into().unwrap())
-}
-
-#[inline(always)]
-fn write_u32(val: u32, buf: &mut Vec<u8>) {
-    buf.extend_from_slice(&val.to_le_bytes());
-}
+use owned_read::OwnedRead;
 
 pub struct SkipSerializer {
     buffer: Vec<u8>,
+    prev_doc: DocId,
 }
 
 impl SkipSerializer {
     pub fn new() -> SkipSerializer {
-        SkipSerializer { buffer: Vec::new() }
+        SkipSerializer {
+            buffer: Vec::new(),
+            prev_doc: 0u32,
+        }
     }
 
     pub fn write_doc(&mut self, last_doc: DocId, doc_num_bits: u8) {
-        write_u32(last_doc, &mut self.buffer);
+        assert!(
+            last_doc > self.prev_doc,
+            "write_doc(...) called with non-increasing doc ids. \
+             Did you forget to call clear maybe?"
+        );
+        let delta_doc = last_doc - self.prev_doc;
+        self.prev_doc = last_doc;
+        delta_doc.serialize(&mut self.buffer).unwrap();
         self.buffer.push(doc_num_bits);
     }
 
@@ -49,13 +36,16 @@ impl SkipSerializer {
     }
 
     pub fn write_total_term_freq(&mut self, tf_sum: u32) {
-        write_u32(tf_sum, &mut self.buffer);
+        tf_sum
+            .serialize(&mut self.buffer)
+            .expect("Should never fail");
     }
 
     pub fn write_blockwand_max(&mut self, fieldnorm_id: u8, term_freq: u32) {
-        let block_wand_tf = encode_block_wand_max_tf(term_freq);
-        self.buffer
-            .extend_from_slice(&[fieldnorm_id, block_wand_tf]);
+        self.buffer.push(fieldnorm_id);
+        let mut buf = [0u8; 8];
+        let bytes = serialize_vint_u32(term_freq, &mut buf);
+        self.buffer.extend_from_slice(bytes);
     }
 
     pub fn data(&self) -> &[u8] {
@@ -63,6 +53,7 @@ impl SkipSerializer {
     }
 
     pub fn clear(&mut self) {
+        self.prev_doc = 0u32;
         self.buffer.clear();
     }
 }
@@ -71,7 +62,7 @@ impl SkipSerializer {
 pub(crate) struct SkipReader {
     last_doc_in_block: DocId,
     pub(crate) last_doc_in_previous_block: DocId,
-    owned_read: OwnedBytes,
+    owned_read: OwnedRead,
     skip_info: IndexRecordOption,
     byte_offset: usize,
     remaining_docs: u32, // number of docs remaining, including the
@@ -102,7 +93,7 @@ impl Default for BlockInfo {
 }
 
 impl SkipReader {
-    pub fn new(data: OwnedBytes, doc_freq: u32, skip_info: IndexRecordOption) -> SkipReader {
+    pub fn new(data: ReadOnlySource, doc_freq: u32, skip_info: IndexRecordOption) -> SkipReader {
         let mut skip_reader = SkipReader {
             last_doc_in_block: if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
                 0
@@ -110,7 +101,7 @@ impl SkipReader {
                 TERMINATED
             },
             last_doc_in_previous_block: 0u32,
-            owned_read: data,
+            owned_read: OwnedRead::new(data),
             skip_info,
             block_info: BlockInfo::VInt { num_docs: doc_freq },
             byte_offset: 0,
@@ -123,14 +114,14 @@ impl SkipReader {
         skip_reader
     }
 
-    pub fn reset(&mut self, data: OwnedBytes, doc_freq: u32) {
+    pub fn reset(&mut self, data: ReadOnlySource, doc_freq: u32) {
         self.last_doc_in_block = if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
             0
         } else {
             TERMINATED
         };
         self.last_doc_in_previous_block = 0u32;
-        self.owned_read = data;
+        self.owned_read = OwnedRead::new(data);
         self.block_info = BlockInfo::VInt { num_docs: doc_freq };
         self.byte_offset = 0;
         self.remaining_docs = doc_freq;
@@ -163,19 +154,17 @@ impl SkipReader {
         self.position_offset
     }
 
-    #[inline(always)]
     pub fn byte_offset(&self) -> usize {
         self.byte_offset
     }
 
     fn read_block_info(&mut self) {
-        let bytes = self.owned_read.as_slice();
-        let advance_len: usize;
-        self.last_doc_in_block = read_u32(bytes);
-        let doc_num_bits = bytes[4];
+        let doc_delta = u32::deserialize(&mut self.owned_read).expect("Skip data corrupted");
+        self.last_doc_in_block += doc_delta as DocId;
+        let doc_num_bits = self.owned_read.get(0);
         match self.skip_info {
             IndexRecordOption::Basic => {
-                advance_len = 5;
+                self.owned_read.advance(1);
                 self.block_info = BlockInfo::BitPacked {
                     doc_num_bits,
                     tf_num_bits: 0,
@@ -185,10 +174,11 @@ impl SkipReader {
                 };
             }
             IndexRecordOption::WithFreqs => {
-                let tf_num_bits = bytes[5];
-                let block_wand_fieldnorm_id = bytes[6];
-                let block_wand_term_freq = decode_block_wand_max_tf(bytes[7]);
-                advance_len = 8;
+                let tf_num_bits = self.owned_read.get(1);
+                let block_wand_fieldnorm_id = self.owned_read.get(2);
+                let data = &self.owned_read.as_ref()[3..];
+                let (block_wand_term_freq, num_bytes) = read_u32_vint_no_advance(data);
+                self.owned_read.advance(3 + num_bytes);
                 self.block_info = BlockInfo::BitPacked {
                     doc_num_bits,
                     tf_num_bits,
@@ -198,11 +188,13 @@ impl SkipReader {
                 };
             }
             IndexRecordOption::WithFreqsAndPositions => {
-                let tf_num_bits = bytes[5];
-                let tf_sum = read_u32(&bytes[6..10]);
-                let block_wand_fieldnorm_id = bytes[10];
-                let block_wand_term_freq = decode_block_wand_max_tf(bytes[11]);
-                advance_len = 12;
+                let tf_num_bits = self.owned_read.get(1);
+                self.owned_read.advance(2);
+                let tf_sum = u32::deserialize(&mut self.owned_read).expect("Failed reading tf_sum");
+                let block_wand_fieldnorm_id = self.owned_read.get(0);
+                self.owned_read.advance(1);
+                let block_wand_term_freq =
+                    VInt::deserialize_u64(&mut self.owned_read).unwrap() as u32;
                 self.block_info = BlockInfo::BitPacked {
                     doc_num_bits,
                     tf_num_bits,
@@ -212,7 +204,6 @@ impl SkipReader {
                 };
             }
         }
-        self.owned_read.advance(advance_len);
     }
 
     pub fn block_info(&self) -> BlockInfo {
@@ -271,27 +262,9 @@ mod tests {
     use super::BlockInfo;
     use super::IndexRecordOption;
     use super::{SkipReader, SkipSerializer};
-    use crate::directory::OwnedBytes;
+    use crate::directory::ReadOnlySource;
     use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
 
-    #[test]
-    fn test_encode_block_wand_max_tf() {
-        for tf in 0..255 {
-            assert_eq!(super::encode_block_wand_max_tf(tf), tf as u8);
-        }
-        for &tf in &[255, 256, 1_000_000, u32::MAX] {
-            assert_eq!(super::encode_block_wand_max_tf(tf), 255);
-        }
-    }
-
-    #[test]
-    fn test_decode_block_wand_max_tf() {
-        for tf in 0..255 {
-            assert_eq!(super::decode_block_wand_max_tf(tf), tf as u32);
-        }
-        assert_eq!(super::decode_block_wand_max_tf(255), u32::MAX);
-    }
-
     #[test]
     fn test_skip_with_freq() {
         let buf = {
@@ -305,8 +278,11 @@ mod tests {
             skip_serializer.data().to_owned()
         };
         let doc_freq = 3u32 + (COMPRESSION_BLOCK_SIZE * 2) as u32;
-        let mut skip_reader =
-            SkipReader::new(OwnedBytes::new(buf), doc_freq, IndexRecordOption::WithFreqs);
+        let mut skip_reader = SkipReader::new(
+            ReadOnlySource::new(buf),
+            doc_freq,
+            IndexRecordOption::WithFreqs,
+        );
         assert_eq!(skip_reader.last_doc_in_block(), 1u32);
         assert_eq!(
             skip_reader.block_info,
@@ -347,8 +323,11 @@ mod tests {
             skip_serializer.data().to_owned()
         };
         let doc_freq = 3u32 + (COMPRESSION_BLOCK_SIZE * 2) as u32;
-        let mut skip_reader =
-            SkipReader::new(OwnedBytes::new(buf), doc_freq, IndexRecordOption::Basic);
+        let mut skip_reader = SkipReader::new(
+            ReadOnlySource::from(buf),
+            doc_freq,
+            IndexRecordOption::Basic,
+        );
         assert_eq!(skip_reader.last_doc_in_block(), 1u32);
         assert_eq!(
             skip_reader.block_info(),
@@ -388,8 +367,11 @@ mod tests {
             skip_serializer.data().to_owned()
         };
         let doc_freq = COMPRESSION_BLOCK_SIZE as u32;
-        let mut skip_reader =
-            SkipReader::new(OwnedBytes::new(buf), doc_freq, IndexRecordOption::Basic);
+        let mut skip_reader = SkipReader::new(
+            ReadOnlySource::from(buf),
+            doc_freq,
+            IndexRecordOption::Basic,
+        );
         assert_eq!(skip_reader.last_doc_in_block(), 1u32);
         assert_eq!(
             skip_reader.block_info(),

src/postings/stacker/expull.rs

@@ -206,8 +206,8 @@ mod tests {
     fn test_stack_long() {
         let mut heap = MemoryArena::new();
         let mut stack = ExpUnrolledLinkedList::new();
-        let data: Vec<u32> = (0..100).collect();
-        for &el in &data {
+        let source: Vec<u32> = (0..100).collect();
+        for &el in &source {
             assert!(stack
                 .writer(&mut heap)
                 .write_u32::<LittleEndian>(el)
@@ -221,7 +221,7 @@ mod tests {
             result.push(LittleEndian::read_u32(&remaining[..4]));
             remaining = &remaining[4..];
         }
-        assert_eq!(&result[..], &data[..]);
+        assert_eq!(&result[..], &source[..]);
     }
 
     #[test]

src/postings/term_info.rs

@@ -7,50 +7,35 @@ use std::io;
 pub struct TermInfo {
     /// Number of documents in the segment containing the term
     pub doc_freq: u32,
-    /// Start offset of the posting list within the postings (`.idx`) file.
-    pub postings_start_offset: u64,
-    /// Stop offset of the posting list within the postings (`.idx`) file.
-    /// The byte range is `[start_offset..stop_offset)`.
-    pub postings_stop_offset: u64,
+    /// Start offset within the postings (`.idx`) file.
+    pub postings_offset: u64,
     /// Start offset of the first block within the position (`.pos`) file.
     pub positions_idx: u64,
 }
 
-impl TermInfo {
-    pub(crate) fn posting_num_bytes(&self) -> u32 {
-        let num_bytes = self.postings_stop_offset - self.postings_start_offset;
-        assert!(num_bytes <= std::u32::MAX as u64);
-        num_bytes as u32
-    }
-}
-
 impl FixedSize for TermInfo {
     /// Size required for the binary serialization of a `TermInfo` object.
     /// This is large, but in practise, `TermInfo` are encoded in blocks and
     /// only the first `TermInfo` of a block is serialized uncompressed.
     /// The subsequent `TermInfo` are delta encoded and bitpacked.
-    const SIZE_IN_BYTES: usize = 2 * u32::SIZE_IN_BYTES + 2 * u64::SIZE_IN_BYTES;
+    const SIZE_IN_BYTES: usize = u32::SIZE_IN_BYTES + 2 * u64::SIZE_IN_BYTES;
 }
 
 impl BinarySerializable for TermInfo {
     fn serialize<W: io::Write>(&self, writer: &mut W) -> io::Result<()> {
         self.doc_freq.serialize(writer)?;
-        self.postings_start_offset.serialize(writer)?;
-        self.posting_num_bytes().serialize(writer)?;
+        self.postings_offset.serialize(writer)?;
         self.positions_idx.serialize(writer)?;
         Ok(())
     }
 
     fn deserialize<R: io::Read>(reader: &mut R) -> io::Result<Self> {
         let doc_freq = u32::deserialize(reader)?;
-        let postings_start_offset = u64::deserialize(reader)?;
-        let postings_num_bytes = u32::deserialize(reader)?;
-        let postings_stop_offset = postings_start_offset + u64::from(postings_num_bytes);
+        let postings_offset = u64::deserialize(reader)?;
         let positions_idx = u64::deserialize(reader)?;
         Ok(TermInfo {
             doc_freq,
-            postings_start_offset,
-            postings_stop_offset,
+            postings_offset,
             positions_idx,
         })
     }

src/query/all_query.rs

@@ -83,7 +83,7 @@ mod tests {
         let 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().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
         index_writer.add_document(doc!(field=>"aaa"));
         index_writer.add_document(doc!(field=>"bbb"));
         index_writer.commit().unwrap();

src/query/automaton_weight.rs

@@ -5,9 +5,9 @@ use crate::query::{BitSetDocSet, Explanation};
 use crate::query::{Scorer, Weight};
 use crate::schema::{Field, IndexRecordOption};
 use crate::termdict::{TermDictionary, TermStreamer};
+use crate::Result;
 use crate::TantivyError;
 use crate::{DocId, Score};
-use std::io;
 use std::sync::Arc;
 use tantivy_fst::Automaton;
 
@@ -20,7 +20,6 @@ pub struct AutomatonWeight<A> {
 impl<A> AutomatonWeight<A>
 where
     A: Automaton + Send + Sync + 'static,
-    A::State: Clone,
 {
     /// Create a new AutomationWeight
     pub fn new<IntoArcA: Into<Arc<A>>>(field: Field, automaton: IntoArcA) -> AutomatonWeight<A> {
@@ -30,10 +29,7 @@ where
         }
     }
 
-    fn automaton_stream<'a>(
-        &'a self,
-        term_dict: &'a TermDictionary,
-    ) -> io::Result<TermStreamer<'a, &'a A>> {
+    fn automaton_stream<'a>(&'a self, term_dict: &'a TermDictionary) -> TermStreamer<'a, &'a A> {
         let automaton: &A = &*self.automaton;
         let term_stream_builder = term_dict.search(automaton);
         term_stream_builder.into_stream()
@@ -43,18 +39,17 @@ where
 impl<A> Weight for AutomatonWeight<A>
 where
     A: Automaton + Send + Sync + 'static,
-    A::State: Clone,
 {
-    fn scorer(&self, reader: &SegmentReader, boost: Score) -> crate::Result<Box<dyn Scorer>> {
+    fn scorer(&self, reader: &SegmentReader, boost: Score) -> Result<Box<dyn Scorer>> {
         let max_doc = reader.max_doc();
         let mut doc_bitset = BitSet::with_max_value(max_doc);
-        let inverted_index = reader.inverted_index(self.field)?;
+        let inverted_index = reader.inverted_index(self.field);
         let term_dict = inverted_index.terms();
-        let mut term_stream = self.automaton_stream(term_dict)?;
+        let mut term_stream = self.automaton_stream(term_dict);
         while term_stream.advance() {
             let term_info = term_stream.value();
             let mut block_segment_postings = inverted_index
-                .read_block_postings_from_terminfo(term_info, IndexRecordOption::Basic)?;
+                .read_block_postings_from_terminfo(term_info, IndexRecordOption::Basic);
             loop {
                 let docs = block_segment_postings.docs();
                 if docs.is_empty() {
@@ -71,7 +66,7 @@ where
         Ok(Box::new(const_scorer))
     }
 
-    fn explain(&self, reader: &SegmentReader, doc: DocId) -> crate::Result<Explanation> {
+    fn explain(&self, reader: &SegmentReader, doc: DocId) -> Result<Explanation> {
         let mut scorer = self.scorer(reader, 1.0)?;
         if scorer.seek(doc) == doc {
             Ok(Explanation::new("AutomatonScorer", 1.0))
@@ -96,7 +91,7 @@ mod tests {
         let mut schema = Schema::builder();
         let title = schema.add_text_field("title", STRING);
         let index = Index::create_in_ram(schema.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!(title=>"abc"));
         index_writer.add_document(doc!(title=>"bcd"));
         index_writer.add_document(doc!(title=>"abcd"));
@@ -104,7 +99,6 @@ mod tests {
         index
     }
 
-    #[derive(Clone, Copy)]
     enum State {
         Start,
         NotMatching,

src/query/bm25.rs

@@ -52,7 +52,7 @@ impl BM25Weight {
         }
     }
 
-    pub fn for_terms(searcher: &Searcher, terms: &[Term]) -> crate::Result<BM25Weight> {
+    pub fn for_terms(searcher: &Searcher, terms: &[Term]) -> BM25Weight {
         assert!(!terms.is_empty(), "BM25 requires at least one term");
         let field = terms[0].field();
         for term in &terms[1..] {
@@ -66,27 +66,25 @@ impl BM25Weight {
         let mut total_num_tokens = 0u64;
         let mut total_num_docs = 0u64;
         for segment_reader in searcher.segment_readers() {
-            let inverted_index = segment_reader.inverted_index(field)?;
+            let inverted_index = segment_reader.inverted_index(field);
             total_num_tokens += inverted_index.total_num_tokens();
             total_num_docs += u64::from(segment_reader.max_doc());
         }
         let average_fieldnorm = total_num_tokens as Score / total_num_docs as Score;
 
         if terms.len() == 1 {
-            let term_doc_freq = searcher.doc_freq(&terms[0])?;
-            Ok(BM25Weight::for_one_term(
-                term_doc_freq,
-                total_num_docs,
-                average_fieldnorm,
-            ))
+            let term_doc_freq = searcher.doc_freq(&terms[0]);
+            BM25Weight::for_one_term(term_doc_freq, total_num_docs, average_fieldnorm)
         } else {
-            let mut idf_sum: Score = 0.0;
-            for term in terms {
-                let term_doc_freq = searcher.doc_freq(term)?;
-                idf_sum += idf(term_doc_freq, total_num_docs);
-            }
-            let idf_explain = Explanation::new("idf", idf_sum);
-            Ok(BM25Weight::new(idf_explain, average_fieldnorm))
+            let idf = terms
+                .iter()
+                .map(|term| {
+                    let term_doc_freq = searcher.doc_freq(term);
+                    idf(term_doc_freq, total_num_docs)
+                })
+                .sum::<Score>();
+            let idf_explain = Explanation::new("idf", idf);
+            BM25Weight::new(idf_explain, average_fieldnorm)
         }
     }
 
@@ -106,7 +104,7 @@ impl BM25Weight {
         BM25Weight::new(idf_explain, avg_fieldnorm)
     }
 
-    pub(crate) fn new(idf_explain: Explanation, average_fieldnorm: Score) -> BM25Weight {
+    fn new(idf_explain: Explanation, average_fieldnorm: Score) -> BM25Weight {
         let weight = idf_explain.value() * (1.0 + K1);
         BM25Weight {
             idf_explain,

src/query/boolean_query/block_wand.rs

@@ -4,6 +4,19 @@ use crate::{DocId, DocSet, Score, TERMINATED};
 use std::ops::Deref;
 use std::ops::DerefMut;
 
+fn is_sorted<I: Iterator<Item = DocId>>(mut it: I) -> bool {
+    if let Some(first) = it.next() {
+        let mut prev = first;
+        for doc in it {
+            if doc < prev {
+                return false;
+            }
+            prev = doc;
+        }
+    }
+    true
+}
+
 /// Takes a term_scorers sorted by their current doc() and a threshold and returns
 /// Returns (pivot_len, pivot_ord) defined as follows:
 /// - `pivot_doc` lowest document that has a chance of exceeding (>) the threshold score.
@@ -42,12 +55,37 @@ fn find_pivot_doc(
     Some((before_pivot_len, pivot_len, pivot_doc))
 }
 
+struct TermScorerWithMaxScore<'a> {
+    scorer: &'a mut TermScorer,
+    max_score: Score,
+}
+
+impl<'a> From<&'a mut TermScorer> for TermScorerWithMaxScore<'a> {
+    fn from(scorer: &'a mut TermScorer) -> Self {
+        let max_score = scorer.max_score();
+        TermScorerWithMaxScore { scorer, max_score }
+    }
+}
+
+impl<'a> Deref for TermScorerWithMaxScore<'a> {
+    type Target = TermScorer;
+
+    fn deref(&self) -> &Self::Target {
+        self.scorer
+    }
+}
+
+impl<'a> DerefMut for TermScorerWithMaxScore<'a> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        self.scorer
+    }
+}
+
 // Before and after calling this method, scorers need to be sorted by their `.doc()`.
 fn block_max_was_too_low_advance_one_scorer(
     scorers: &mut Vec<TermScorerWithMaxScore>,
     pivot_len: usize,
 ) {
-    debug_assert!(is_sorted(scorers.iter().map(|scorer| scorer.doc())));
     let mut scorer_to_seek = pivot_len - 1;
     let mut doc_to_seek_after = scorers[scorer_to_seek].doc();
     for scorer_ord in (0..pivot_len - 1).rev() {
@@ -64,7 +102,6 @@ fn block_max_was_too_low_advance_one_scorer(
     }
     scorers[scorer_to_seek].seek(doc_to_seek_after + 1);
     restore_ordering(scorers, scorer_to_seek);
-    debug_assert!(is_sorted(scorers.iter().map(|scorer| scorer.doc())));
 }
 
 // Given a list of term_scorers and a `ord` and assuming that `term_scorers[ord]` is sorted
@@ -140,99 +177,64 @@ pub fn block_wand(
         .map(TermScorerWithMaxScore::from)
         .collect();
     scorers.sort_by_key(|scorer| scorer.doc());
-    // At this point we need to ensure that the scorers are sorted!
-    debug_assert!(is_sorted(scorers.iter().map(|scorer| scorer.doc())));
-    while let Some((before_pivot_len, pivot_len, pivot_doc)) =
-        find_pivot_doc(&scorers[..], threshold)
-    {
+    loop {
+        // At this point we need to ensure that the scorers are sorted!
         debug_assert!(is_sorted(scorers.iter().map(|scorer| scorer.doc())));
-        debug_assert_ne!(pivot_doc, TERMINATED);
-        debug_assert!(before_pivot_len < pivot_len);
+        if let Some((before_pivot_len, pivot_len, pivot_doc)) =
+            find_pivot_doc(&scorers[..], threshold)
+        {
+            debug_assert_ne!(pivot_doc, TERMINATED);
+            debug_assert!(before_pivot_len < pivot_len);
 
-        let block_max_score_upperbound: Score = scorers[..pivot_len]
-            .iter_mut()
-            .map(|scorer| {
-                scorer.shallow_seek(pivot_doc);
-                scorer.block_max_score()
-            })
-            .sum();
+            let block_max_score_upperbound: Score = scorers[..pivot_len]
+                .iter_mut()
+                .map(|scorer| {
+                    scorer.shallow_seek(pivot_doc);
+                    scorer.block_max_score()
+                })
+                .sum();
 
-        // Beware after shallow advance, skip readers can be in advance compared to
-        // the segment posting lists.
-        //
-        // `block_segment_postings.load_block()` need to be called separately.
-        if block_max_score_upperbound <= threshold {
-            // Block max condition was not reached
-            // We could get away by simply advancing the scorers to DocId + 1 but it would
-            // be inefficient. The optimization requires proper explanation and was
-            // isolated in a different function.
-            block_max_was_too_low_advance_one_scorer(&mut scorers, pivot_len);
-            continue;
-        }
-
-        // Block max condition is observed.
-        //
-        // Let's try and advance all scorers before the pivot to the pivot.
-        if !align_scorers(&mut scorers, pivot_doc, before_pivot_len) {
-            // At least of the scorer does not contain the pivot.
+            // Beware after shallow advance, skip readers can be in advance compared to
+            // the segment posting lists.
             //
-            // Let's stop scoring this pivot and go through the pivot selection again.
-            // Note that the current pivot is not necessarily a bad candidate and it
-            // may be picked again.
-            continue;
-        }
-
-        // At this point, all scorers are positioned on the doc.
-        let score = scorers[..pivot_len]
-            .iter_mut()
-            .map(|scorer| scorer.score())
-            .sum();
-        if score > threshold {
-            threshold = callback(pivot_doc, score);
-        }
-        // let's advance all of the scorers that are currently positioned on the pivot.
-        advance_all_scorers_on_pivot(&mut scorers, pivot_len);
-    }
-}
-
-struct TermScorerWithMaxScore<'a> {
-    scorer: &'a mut TermScorer,
-    max_score: Score,
-}
-
-impl<'a> From<&'a mut TermScorer> for TermScorerWithMaxScore<'a> {
-    fn from(scorer: &'a mut TermScorer) -> Self {
-        let max_score = scorer.max_score();
-        TermScorerWithMaxScore { scorer, max_score }
-    }
-}
-
-impl<'a> Deref for TermScorerWithMaxScore<'a> {
-    type Target = TermScorer;
-
-    fn deref(&self) -> &Self::Target {
-        self.scorer
-    }
-}
-
-impl<'a> DerefMut for TermScorerWithMaxScore<'a> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        self.scorer
-    }
-}
-
-fn is_sorted<I: Iterator<Item = DocId>>(mut it: I) -> bool {
-    if let Some(first) = it.next() {
-        let mut prev = first;
-        for doc in it {
-            if doc < prev {
-                return false;
+            // `block_segment_postings.load_block()` need to be called separately.
+            if block_max_score_upperbound <= threshold {
+                // Block max condition was not reached
+                // We could get away by simply advancing the scorers to DocId + 1 but it would
+                // be inefficient. The optimization requires proper explanation and was
+                // isolated in a different function.
+                block_max_was_too_low_advance_one_scorer(&mut scorers, pivot_len);
+                continue;
             }
-            prev = doc;
+
+            // Block max condition is observed.
+            //
+            // Let's try and advance all scorers before the pivot to the pivot.
+            if !align_scorers(&mut scorers, pivot_doc, before_pivot_len) {
+                // At least of the scorer does not contain the pivot.
+                //
+                // Let's stop scoring this pivot and go through the pivot selection again.
+                // Note that the current pivot is not necessarily a bad candidate and it
+                // may be picked again.
+                continue;
+            }
+
+            // At this point, all scorers are positioned on the doc.
+            let score = scorers[..pivot_len]
+                .iter_mut()
+                .map(|scorer| scorer.score())
+                .sum();
+            if score > threshold {
+                threshold = callback(pivot_doc, score);
+            }
+            // let's advance all of the scorers that are currently positioned on the pivot.
+            advance_all_scorers_on_pivot(&mut scorers, pivot_len);
+        } else {
+            return;
         }
     }
-    true
 }
+
 #[cfg(test)]
 mod tests {
     use crate::query::score_combiner::SumCombiner;
@@ -246,21 +248,17 @@ mod tests {
     use std::iter;
 
     struct Float(Score);
-
     impl Eq for Float {}
-
     impl PartialEq for Float {
         fn eq(&self, other: &Self) -> bool {
             self.cmp(&other) == Ordering::Equal
         }
     }
-
     impl PartialOrd for Float {
         fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
             Some(self.cmp(other))
         }
     }
-
     impl Ord for Float {
         fn cmp(&self, other: &Self) -> Ordering {
             other.0.partial_cmp(&self.0).unwrap_or(Ordering::Equal)
@@ -268,7 +266,7 @@ mod tests {
     }
 
     fn nearly_equals(left: Score, right: Score) -> bool {
-        (left - right).abs() < 0.0001 * (left + right).abs()
+        (left - right).abs() < 0.000001 * (left + right).abs()
     }
 
     fn compute_checkpoints_for_each_pruning(
@@ -424,116 +422,9 @@ mod tests {
         }
     }
 
-    #[test]
-    fn test_fn_reproduce_proptest() {
-        let postings_lists = &[
-            vec![
-                (0, 1),
-                (1, 1),
-                (2, 1),
-                (3, 1),
-                (4, 1),
-                (6, 1),
-                (7, 7),
-                (8, 1),
-                (10, 1),
-                (12, 1),
-                (13, 1),
-                (14, 1),
-                (15, 1),
-                (16, 1),
-                (19, 1),
-                (20, 1),
-                (21, 1),
-                (22, 1),
-                (24, 1),
-                (25, 1),
-                (26, 1),
-                (28, 1),
-                (30, 1),
-                (31, 1),
-                (33, 1),
-                (34, 1),
-                (35, 1),
-                (36, 95),
-                (37, 1),
-                (39, 1),
-                (41, 1),
-                (44, 1),
-                (46, 1),
-            ],
-            vec![
-                (0, 5),
-                (2, 1),
-                (4, 1),
-                (5, 84),
-                (6, 47),
-                (7, 26),
-                (8, 50),
-                (9, 34),
-                (11, 73),
-                (12, 11),
-                (13, 51),
-                (14, 45),
-                (15, 18),
-                (18, 60),
-                (19, 80),
-                (20, 63),
-                (23, 79),
-                (24, 69),
-                (26, 35),
-                (28, 82),
-                (29, 19),
-                (30, 2),
-                (31, 7),
-                (33, 40),
-                (34, 1),
-                (35, 33),
-                (36, 27),
-                (37, 24),
-                (38, 65),
-                (39, 32),
-                (40, 85),
-                (41, 1),
-                (42, 69),
-                (43, 11),
-                (45, 45),
-                (47, 97),
-            ],
-            vec![
-                (2, 1),
-                (4, 1),
-                (7, 94),
-                (8, 1),
-                (9, 1),
-                (10, 1),
-                (12, 1),
-                (15, 1),
-                (22, 1),
-                (23, 1),
-                (26, 1),
-                (27, 1),
-                (32, 1),
-                (33, 1),
-                (34, 1),
-                (36, 96),
-                (39, 1),
-                (41, 1),
-            ],
-        ];
-        let fieldnorms = &[
-            685, 239, 780, 564, 664, 827, 5, 56, 930, 887, 263, 665, 167, 127, 120, 919, 292, 92,
-            489, 734, 814, 724, 700, 304, 128, 779, 311, 877, 774, 15, 866, 368, 894, 371, 982,
-            502, 507, 669, 680, 76, 594, 626, 578, 331, 170, 639, 665, 186,
-        ][..];
-        test_block_wand_aux(postings_lists, fieldnorms);
-    }
-
     proptest! {
         #![proptest_config(ProptestConfig::with_cases(500))]
-        #[ignore]
         #[test]
-        #[ignore]
         fn test_block_wand_three_term_scorers((posting_lists, fieldnorms) in gen_term_scorers(3)) {
             test_block_wand_aux(&posting_lists[..], &fieldnorms[..]);
         }

src/query/boolean_query/boolean_query.rs

@@ -83,7 +83,7 @@ use std::collections::BTreeSet;
 ///    ];
 ///    // Make a BooleanQuery equivalent to
 ///    // title:+diary title:-girl
-///    let diary_must_and_girl_mustnot = BooleanQuery::new(queries_with_occurs1);
+///    let diary_must_and_girl_mustnot = BooleanQuery::from(queries_with_occurs1);
 ///    let count1 = searcher.search(&diary_must_and_girl_mustnot, &Count)?;
 ///    assert_eq!(count1, 1);
 ///
@@ -93,7 +93,7 @@ use std::collections::BTreeSet;
 ///        IndexRecordOption::Basic,
 ///    ));
 ///    // "title:diary OR title:cow"
-///    let title_diary_or_cow = BooleanQuery::new(vec![
+///    let title_diary_or_cow = BooleanQuery::from(vec![
 ///        (Occur::Should, diary_term_query.box_clone()),
 ///        (Occur::Should, cow_term_query),
 ///    ]);
@@ -108,7 +108,7 @@ use std::collections::BTreeSet;
 ///    // You can combine subqueries of different types into 1 BooleanQuery:
 ///    // `TermQuery` and `PhraseQuery`
 ///    // "title:diary OR "dairy cow"
-///    let term_of_phrase_query = BooleanQuery::new(vec![
+///    let term_of_phrase_query = BooleanQuery::from(vec![
 ///        (Occur::Should, diary_term_query.box_clone()),
 ///        (Occur::Should, phrase_query.box_clone()),
 ///    ]);
@@ -117,7 +117,7 @@ use std::collections::BTreeSet;
 ///
 ///    // You can nest one BooleanQuery inside another
 ///    // body:found AND ("title:diary OR "dairy cow")
-///    let nested_query = BooleanQuery::new(vec![
+///    let nested_query = BooleanQuery::from(vec![
 ///        (Occur::Must, body_term_query),
 ///        (Occur::Must, Box::new(term_of_phrase_query))
 ///    ]);
@@ -143,7 +143,7 @@ impl Clone for BooleanQuery {
 
 impl From<Vec<(Occur, Box<dyn Query>)>> for BooleanQuery {
     fn from(subqueries: Vec<(Occur, Box<dyn Query>)>) -> BooleanQuery {
-        BooleanQuery::new(subqueries)
+        BooleanQuery { subqueries }
     }
 }
 
@@ -167,23 +167,6 @@ impl Query for BooleanQuery {
 }
 
 impl BooleanQuery {
-    /// Creates a new boolean query.
-    pub fn new(subqueries: Vec<(Occur, Box<dyn Query>)>) -> BooleanQuery {
-        BooleanQuery { subqueries }
-    }
-
-    /// Returns the intersection of the queries.
-    pub fn intersection(queries: Vec<Box<dyn Query>>) -> BooleanQuery {
-        let subqueries = queries.into_iter().map(|s| (Occur::Must, s)).collect();
-        BooleanQuery::new(subqueries)
-    }
-
-    /// Returns the union of the queries.
-    pub fn union(queries: Vec<Box<dyn Query>>) -> BooleanQuery {
-        let subqueries = queries.into_iter().map(|s| (Occur::Should, s)).collect();
-        BooleanQuery::new(subqueries)
-    }
-
     /// Helper method to create a boolean query matching a given list of terms.
     /// The resulting query is a disjunction of the terms.
     pub fn new_multiterms_query(terms: Vec<Term>) -> BooleanQuery {
@@ -195,7 +178,7 @@ impl BooleanQuery {
                 (Occur::Should, term_query)
             })
             .collect();
-        BooleanQuery::new(occur_term_queries)
+        BooleanQuery::from(occur_term_queries)
     }
 
     /// Deconstructed view of the clauses making up this query.
@@ -203,77 +186,3 @@ impl BooleanQuery {
         &self.subqueries[..]
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::BooleanQuery;
-    use crate::collector::DocSetCollector;
-    use crate::query::{QueryClone, TermQuery};
-    use crate::schema::{IndexRecordOption, Schema, TEXT};
-    use crate::{DocAddress, Index, Term};
-
-    fn create_test_index() -> crate::Result<Index> {
-        let mut schema_builder = Schema::builder();
-        let text = schema_builder.add_text_field("text", TEXT);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut writer = index.writer_for_tests().unwrap();
-        writer.add_document(doc!(text=>"b c"));
-        writer.add_document(doc!(text=>"a c"));
-        writer.add_document(doc!(text=>"a b"));
-        writer.add_document(doc!(text=>"a d"));
-        writer.commit()?;
-        Ok(index)
-    }
-
-    #[test]
-    fn test_union() -> crate::Result<()> {
-        let index = create_test_index()?;
-        let searcher = index.reader()?.searcher();
-        let text = index.schema().get_field("text").unwrap();
-        let term_a = TermQuery::new(Term::from_field_text(text, "a"), IndexRecordOption::Basic);
-        let term_d = TermQuery::new(Term::from_field_text(text, "d"), IndexRecordOption::Basic);
-        let union_ad = BooleanQuery::union(vec![term_a.box_clone(), term_d.box_clone()]);
-        let docs = searcher.search(&union_ad, &DocSetCollector)?;
-        assert_eq!(
-            docs,
-            vec![
-                DocAddress(0u32, 1u32),
-                DocAddress(0u32, 2u32),
-                DocAddress(0u32, 3u32)
-            ]
-            .into_iter()
-            .collect()
-        );
-        Ok(())
-    }
-
-    #[test]
-    fn test_intersection() -> crate::Result<()> {
-        let index = create_test_index()?;
-        let searcher = index.reader()?.searcher();
-        let text = index.schema().get_field("text").unwrap();
-        let term_a = TermQuery::new(Term::from_field_text(text, "a"), IndexRecordOption::Basic);
-        let term_b = TermQuery::new(Term::from_field_text(text, "b"), IndexRecordOption::Basic);
-        let term_c = TermQuery::new(Term::from_field_text(text, "c"), IndexRecordOption::Basic);
-        let intersection_ab =
-            BooleanQuery::intersection(vec![term_a.box_clone(), term_b.box_clone()]);
-        let intersection_ac =
-            BooleanQuery::intersection(vec![term_a.box_clone(), term_c.box_clone()]);
-        let intersection_bc =
-            BooleanQuery::intersection(vec![term_b.box_clone(), term_c.box_clone()]);
-        {
-            let docs = searcher.search(&intersection_ab, &DocSetCollector)?;
-            assert_eq!(docs, vec![DocAddress(0u32, 2u32)].into_iter().collect());
-        }
-        {
-            let docs = searcher.search(&intersection_ac, &DocSetCollector)?;
-            assert_eq!(docs, vec![DocAddress(0u32, 1u32)].into_iter().collect());
-        }
-        {
-            let docs = searcher.search(&intersection_bc, &DocSetCollector)?;
-            assert_eq!(docs, vec![DocAddress(0u32, 0u32)].into_iter().collect());
-        }
-        Ok(())
-    }
-}

src/query/boolean_query/mod.rs

@@ -32,12 +32,14 @@ mod tests {
         let index = Index::create_in_ram(schema);
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests().unwrap();
-            index_writer.add_document(doc!(text_field => "a b c"));
-            index_writer.add_document(doc!(text_field => "a c"));
-            index_writer.add_document(doc!(text_field => "b c"));
-            index_writer.add_document(doc!(text_field => "a b c d"));
-            index_writer.add_document(doc!(text_field => "d"));
+            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 => "a c"));
+                index_writer.add_document(doc!(text_field => "b c"));
+                index_writer.add_document(doc!(text_field => "a b c d"));
+                index_writer.add_document(doc!(text_field => "d"));
+            }
             assert!(index_writer.commit().is_ok());
         }
         (index, text_field)
@@ -132,29 +134,29 @@ mod tests {
                 .collect::<Vec<DocId>>()
         };
         {
-            let boolean_query = BooleanQuery::new(vec![(Occur::Must, make_term_query("a"))]);
+            let boolean_query = BooleanQuery::from(vec![(Occur::Must, make_term_query("a"))]);
             assert_eq!(matching_docs(&boolean_query), vec![0, 1, 3]);
         }
         {
-            let boolean_query = BooleanQuery::new(vec![(Occur::Should, make_term_query("a"))]);
+            let boolean_query = BooleanQuery::from(vec![(Occur::Should, make_term_query("a"))]);
             assert_eq!(matching_docs(&boolean_query), vec![0, 1, 3]);
         }
         {
-            let boolean_query = BooleanQuery::new(vec![
+            let boolean_query = BooleanQuery::from(vec![
                 (Occur::Should, make_term_query("a")),
                 (Occur::Should, make_term_query("b")),
             ]);
             assert_eq!(matching_docs(&boolean_query), vec![0, 1, 2, 3]);
         }
         {
-            let boolean_query = BooleanQuery::new(vec![
+            let boolean_query = BooleanQuery::from(vec![
                 (Occur::Must, make_term_query("a")),
                 (Occur::Should, make_term_query("b")),
             ]);
             assert_eq!(matching_docs(&boolean_query), vec![0, 1, 3]);
         }
         {
-            let boolean_query = BooleanQuery::new(vec![
+            let boolean_query = BooleanQuery::from(vec![
                 (Occur::Must, make_term_query("a")),
                 (Occur::Should, make_term_query("b")),
                 (Occur::MustNot, make_term_query("d")),
@@ -162,7 +164,7 @@ mod tests {
             assert_eq!(matching_docs(&boolean_query), vec![0, 1]);
         }
         {
-            let boolean_query = BooleanQuery::new(vec![(Occur::MustNot, make_term_query("d"))]);
+            let boolean_query = BooleanQuery::from(vec![(Occur::MustNot, make_term_query("d"))]);
             assert_eq!(matching_docs(&boolean_query), Vec::<u32>::new());
         }
     }
@@ -192,7 +194,7 @@ mod tests {
         let score_doc_4: Score; // score of doc 4 should not be influenced by exclusion
         {
             let boolean_query_no_excluded =
-                BooleanQuery::new(vec![(Occur::Must, make_term_query("d"))]);
+                BooleanQuery::from(vec![(Occur::Must, make_term_query("d"))]);
             let topdocs_no_excluded = matching_topdocs(&boolean_query_no_excluded);
             assert_eq!(topdocs_no_excluded.len(), 2);
             let (top_score, top_doc) = topdocs_no_excluded[0];
@@ -202,7 +204,7 @@ mod tests {
         }
 
         {
-            let boolean_query_two_excluded = BooleanQuery::new(vec![
+            let boolean_query_two_excluded = BooleanQuery::from(vec![
                 (Occur::Must, make_term_query("d")),
                 (Occur::MustNot, make_term_query("a")),
                 (Occur::MustNot, make_term_query("b")),
@@ -222,7 +224,7 @@ 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!(text_field => "a b c"));
             index_writer.add_document(doc!(text_field => "a c"));
             index_writer.add_document(doc!(text_field => "b c"));
@@ -239,7 +241,7 @@ mod tests {
         let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let boolean_query =
-            BooleanQuery::new(vec![(Occur::Should, term_a), (Occur::Should, term_b)]);
+            BooleanQuery::from(vec![(Occur::Should, term_a), (Occur::Should, term_b)]);
         let boolean_weight = boolean_query.weight(&searcher, true).unwrap();
         {
             let mut boolean_scorer = boolean_weight
@@ -279,7 +281,7 @@ mod tests {
         };
 
         {
-            let boolean_query = BooleanQuery::new(vec![
+            let boolean_query = BooleanQuery::from(vec![
                 (Occur::Must, make_term_query("a")),
                 (Occur::Must, make_term_query("b")),
             ]);
@@ -288,29 +290,4 @@ mod tests {
             assert_nearly_equals!(scores[1], 0.84699446);
         }
     }
-
-    #[test]
-    pub fn test_explain() -> crate::Result<()> {
-        let mut schema_builder = Schema::builder();
-        let text = schema_builder.add_text_field("text", STRING);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_with_num_threads(1, 5_000_000)?;
-        index_writer.add_document(doc!(text=>"a"));
-        index_writer.add_document(doc!(text=>"b"));
-        index_writer.commit()?;
-        let searcher = index.reader()?.searcher();
-        let term_a: Box<dyn Query> = Box::new(TermQuery::new(
-            Term::from_field_text(text, "a"),
-            IndexRecordOption::Basic,
-        ));
-        let term_b: Box<dyn Query> = Box::new(TermQuery::new(
-            Term::from_field_text(text, "b"),
-            IndexRecordOption::Basic,
-        ));
-        let query = BooleanQuery::from(vec![(Occur::Should, term_a), (Occur::Should, term_b)]);
-        let explanation = query.explain(&searcher, DocAddress(0, 0u32))?;
-        assert_nearly_equals!(explanation.value(), 0.6931472);
-        Ok(())
-    }
 }

src/query/boost_query.rs

@@ -144,7 +144,7 @@ mod tests {
     fn test_boost_query_explain() {
         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(Document::new());
         assert!(index_writer.commit().is_ok());
         let reader = index.reader().unwrap();
@@ -153,7 +153,7 @@ mod tests {
         let explanation = query.explain(&searcher, DocAddress(0, 0u32)).unwrap();
         assert_eq!(
             explanation.to_pretty_json(),
-            "{\n  \"value\": 0.2,\n  \"description\": \"Boost x0.2 of ...\",\n  \"details\": [\n    {\n      \"value\": 1.0,\n      \"description\": \"AllQuery\",\n      \"context\": []\n    }\n  ],\n  \"context\": []\n}"
+            "{\n  \"value\": 0.2,\n  \"description\": \"Boost x0.2 of ...\",\n  \"details\": [\n    {\n      \"value\": 1.0,\n      \"description\": \"AllQuery\"\n    }\n  ]\n}"
         )
     }
 }

src/query/explanation.rs

@@ -17,7 +17,6 @@ pub struct Explanation {
     description: String,
     #[serde(skip_serializing_if = "Vec::is_empty")]
     details: Vec<Explanation>,
-    context: Vec<String>,
 }
 
 impl fmt::Debug for Explanation {
@@ -33,7 +32,6 @@ impl Explanation {
             value,
             description: description.to_string(),
             details: vec![],
-            context: vec![],
         }
     }
 
@@ -49,11 +47,6 @@ impl Explanation {
         self.details.push(child_explanation);
     }
 
-    /// Adds some extra context to the explanation.
-    pub fn add_context(&mut self, context: String) {
-        self.context.push(context);
-    }
-
     /// Shortcut for `self.details.push(Explanation::new(name, value));`
     pub fn add_const<T: ToString>(&mut self, name: T, value: Score) {
         self.details.push(Explanation::new(name, value));

src/query/fuzzy_query.rs

@@ -177,7 +177,7 @@ mod test {
         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, 10_000_000).unwrap();
             index_writer.add_document(doc!(
                 country_field => "japan",
             ));

src/query/mod.rs

@@ -46,7 +46,7 @@ pub(crate) use self::fuzzy_query::DFAWrapper;
 pub use self::fuzzy_query::FuzzyTermQuery;
 pub use self::intersection::intersect_scorers;
 pub use self::phrase_query::PhraseQuery;
-pub use self::query::{Query, QueryClone};
+pub use self::query::Query;
 pub use self::query_parser::QueryParser;
 pub use self::query_parser::QueryParserError;
 pub use self::range_query::RangeQuery;