persistor

.gitignore

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

CHANGELOG.md

@@ -1,43 +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)
-- Switched to structure logging (via the `slog` crate). (@pmasurel)
-
-Tantivy 0.13.1
-===================
-Made `Query` and `Collector` `Send + Sync`.
-Updated misc dependency versions.
-
-Tantivy 0.13.0
-======================
-Tantivy 0.13 introduce a change in the index format that will require
-you to reindex your index (BlockWAND information are added in the skiplist). 
-The index size increase is minor as this information is only added for
-full blocks.
-If you have a massive index for which reindexing is not an option, please contact me
-so that we can discuss possible solutions.
-
-- Bugfix in `FuzzyTermQuery` not matching terms by prefix when it should (@Peachball)
-- Relaxed constraints on the custom/tweak score functions. At the segment level, they can be mut, and they are not required to be Sync + Send.
-- `MMapDirectory::open` does not return a `Result` anymore.
-- Change in the DocSet and Scorer API. (@fulmicoton). 
-A freshly created DocSet point directly to their first doc. A sentinel value called TERMINATED marks the end of a DocSet.
-`.advance()` returns the new DocId. `Scorer::skip(target)` has been replaced by `Scorer::seek(target)` and returns the resulting DocId.
-As a result, iterating through DocSet now looks as follows
-```rust
-let mut doc = docset.doc();
-while doc != TERMINATED {
-   // ...
-   doc = docset.advance();
-}
-```
-The change made it possible to greatly simplify a lot of the docset's code.
-- Misc internal optimization and introduction of the `Scorer::for_each_pruning` function. (@fulmicoton)
-- Added an offset option to the Top(.*)Collectors. (@robyoung)
-- Added Block WAND. Performance on TOP-K on term-unions should be greatly increased. (@fulmicoton, and special thanks 
-to the PISA team for answering all my questions!)
-
 Tantivy 0.12.0
 ======================
 - Removing static dispatch in tokenizers for simplicity. (#762)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tantivy"
-version = "0.14.0-dev"
+version = "0.12.0"
 authors = ["Paul Masurel <paul.masurel@gmail.com>"]
 license = "MIT"
 categories = ["database-implementations", "data-structures"]
@@ -13,42 +13,42 @@ keywords = ["search", "information", "retrieval"]
 edition = "2018"
 
 [dependencies]
-base64 = "0.12"
-byteorder = "1"
-crc32fast = "1"
-once_cell = "1"
-regex ={version = "1", default-features = false, features = ["std"]}
-tantivy-fst = "0.3"
+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 = "0.2.1"
 memmap = {version = "0.7", optional=true}
-lz4 = {version="1", optional=true}
+lz4 = {version="1.20", optional=true}
 snap = "1"
-tempfile = {version="3", optional=true}
-slog = "2.5"
-slog-stdlog = "4"
-serde = {version="1", features=["derive"]}
-serde_json = "1"
-num_cpus = "1"
+atomicwrites = {version="0.2.2", optional=true}
+tempfile = "3.0"
+log = "0.4"
+serde = {version="1.0", features=["derive"]}
+serde_json = "1.0"
+num_cpus = "1.2"
 fs2={version="0.4", optional=true}
-levenshtein_automata = "0.2"
+levenshtein_automata = "0.1"
 notify = {version="4", optional=true}
 uuid = { version = "0.8", features = ["v4", "serde"] }
 crossbeam = "0.7"
 futures = {version = "0.3",  features=["thread-pool"] }
 owning_ref = "0.4"
-tantivy-query-grammar = { version="0.14.0-dev", path="./query-grammar" }
-stable_deref_trait = "1"
-rust-stemmers = "1"
-downcast-rs = "1"
+stable_deref_trait = "1.0.0"
+rust-stemmers = "1.2"
+downcast-rs = { version="1.0" }
+tantivy-query-grammar = { version="0.12", path="./query-grammar" }
 bitpacking = {version="0.8", default-features = false, features=["bitpacker4x"]}
-census = "0.4"
-fnv = "1"
+census =  {path="../census"}
+fnv = "1.0.6"
 owned-read = "0.4"
-thiserror = "1.0"
-htmlescape = "0.3"
-fail = "0.4"
+failure = "0.1"
+htmlescape = "0.3.1"
+fail = "0.3"
 murmurhash32 = "0.2"
 chrono = "0.4"
-smallvec = "1"
+smallvec = "1.0"
 rayon = "1"
 
 [target.'cfg(windows)'.dependencies]
@@ -58,10 +58,9 @@ winapi = "0.3"
 rand = "0.7"
 maplit = "1"
 matches = "0.1.8"
-proptest = "0.10"
 
 [dev-dependencies.fail]
-version = "0.4"
+version = "0.3"
 features = ["failpoints"]
 
 [profile.release]
@@ -75,7 +74,7 @@ overflow-checks = true
 
 [features]
 default = ["mmap"]
-mmap = ["fs2", "tempfile", "memmap", "notify"]
+mmap = ["atomicwrites", "fs2", "memmap", "notify"]
 lz4-compression = ["lz4"]
 failpoints = ["fail/failpoints"]
 unstable = [] # useful for benches.

README.md

@@ -31,11 +31,12 @@ Tantivy is, in fact, strongly inspired by Lucene's design.
 
 # Benchmark
 
+Tantivy is typically faster than Lucene, but the results depend on 
+the nature of the queries in your workload.
+
 The following [benchmark](https://tantivy-search.github.io/bench/) break downs 
 performance for different type of queries / collection.
 
-Your mileage WILL vary depending on the nature of queries and their load.
-
 # Features
 
 - Full-text search

TODO.md

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

appveyor.yml

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

examples/basic_search.rs

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

examples/custom_collector.rs

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

examples/faceted_search_with_tweaked_score.rs

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

examples/iterating_docs_and_positions.rs

@@ -10,7 +10,7 @@
 // ---
 // Importing tantivy...
 use tantivy::schema::*;
-use tantivy::{doc, DocSet, Index, Postings, TERMINATED};
+use tantivy::{doc, DocId, DocSet, Index, Postings};
 
 fn main() -> tantivy::Result<()> {
     // We first create a schema for the sake of the
@@ -62,11 +62,12 @@ fn main() -> tantivy::Result<()> {
         {
             // this buffer will be used to request for positions
             let mut positions: Vec<u32> = Vec::with_capacity(100);
-            let mut doc_id = segment_postings.doc();
-            while doc_id != TERMINATED {
+            while segment_postings.advance() {
+                // the number of time the term appears in the document.
+                let doc_id: DocId = segment_postings.doc(); //< do not try to access this before calling advance once.
+
                 // This MAY contains deleted documents as well.
                 if segment_reader.is_deleted(doc_id) {
-                    doc_id = segment_postings.advance();
                     continue;
                 }
 
@@ -85,7 +86,6 @@ fn main() -> tantivy::Result<()> {
                 // Doc 2: TermFreq 1: [0]
                 // ```
                 println!("Doc {}: TermFreq {}: {:?}", doc_id, term_freq, positions);
-                doc_id = segment_postings.advance();
             }
         }
     }
@@ -117,16 +117,11 @@ fn main() -> tantivy::Result<()> {
         if let Some(mut block_segment_postings) =
             inverted_index.read_block_postings(&term_the, IndexRecordOption::Basic)
         {
-            loop {
-                let docs = block_segment_postings.docs();
-                if docs.is_empty() {
-                    break;
-                }
+            while block_segment_postings.advance() {
                 // Once again these docs MAY contains deleted documents as well.
                 let docs = block_segment_postings.docs();
                 // Prints `Docs [0, 2].`
                 println!("Docs {:?}", docs);
-                block_segment_postings.advance();
             }
         }
     }

query-grammar/Cargo.toml

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

query-grammar/src/occur.rs

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

query-grammar/src/query_grammar.rs

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

query-grammar/src/user_input_ast.rs

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

src/collector/count_collector.rs

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

src/collector/custom_score_top_collector.rs

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

src/collector/facet_collector.rs

@@ -1,5 +1,6 @@
 use crate::collector::Collector;
 use crate::collector::SegmentCollector;
+use crate::docset::SkipResult;
 use crate::fastfield::FacetReader;
 use crate::schema::Facet;
 use crate::schema::Field;
@@ -187,11 +188,6 @@ pub struct FacetSegmentCollector {
     collapse_facet_ords: Vec<u64>,
 }
 
-enum SkipResult {
-    Found,
-    NotFound,
-}
-
 fn skip<'a, I: Iterator<Item = &'a Facet>>(
     target: &[u8],
     collapse_it: &mut Peekable<I>,
@@ -201,14 +197,14 @@ fn skip<'a, I: Iterator<Item = &'a Facet>>(
             Some(facet_bytes) => match facet_bytes.encoded_str().as_bytes().cmp(target) {
                 Ordering::Less => {}
                 Ordering::Greater => {
-                    return SkipResult::NotFound;
+                    return SkipResult::OverStep;
                 }
                 Ordering::Equal => {
-                    return SkipResult::Found;
+                    return SkipResult::Reached;
                 }
             },
             None => {
-                return SkipResult::NotFound;
+                return SkipResult::End;
             }
         }
         collapse_it.next();
@@ -285,7 +281,7 @@ impl Collector for FacetCollector {
                     // is positionned on a term that has not been processed yet.
                     let skip_result = skip(facet_streamer.key(), &mut collapse_facet_it);
                     match skip_result {
-                        SkipResult::Found => {
+                        SkipResult::Reached => {
                             // we reach a facet we decided to collapse.
                             let collapse_depth = facet_depth(facet_streamer.key());
                             let mut collapsed_id = 0;
@@ -305,7 +301,7 @@ impl Collector for FacetCollector {
                             }
                             break;
                         }
-                        SkipResult::NotFound => {
+                        SkipResult::End | SkipResult::OverStep => {
                             collapse_mapping.push(0);
                             if !facet_streamer.advance() {
                                 break;
@@ -472,7 +468,7 @@ mod tests {
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let num_facets: usize = 3 * 4 * 5;
         let facets: Vec<Facet> = (0..num_facets)
             .map(|mut n| {
@@ -531,7 +527,7 @@ mod tests {
         let facet_field = schema_builder.add_facet_field("facets");
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(
             facet_field => Facet::from_text(&"/subjects/A/a"),
             facet_field => Facet::from_text(&"/subjects/B/a"),
@@ -550,12 +546,12 @@ mod tests {
     }
 
     #[test]
-    fn test_doc_search_by_facet() -> crate::Result<()> {
+    fn test_doc_search_by_facet() {
         let mut schema_builder = Schema::builder();
         let facet_field = schema_builder.add_facet_field("facet");
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(
             facet_field => Facet::from_text(&"/A/A"),
         ));
@@ -568,8 +564,8 @@ 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);
 
@@ -586,17 +582,17 @@ mod tests {
         assert_eq!(count_facet("/A/C"), 1);
         assert_eq!(count_facet("/A/C/A"), 1);
         assert_eq!(count_facet("/C/A"), 0);
-
-        let query_parser = QueryParser::for_index(&index, vec![]);
         {
-            let query = query_parser.parse_query("facet:/A/B")?;
-            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]
@@ -631,7 +627,7 @@ mod tests {
             .collect();
         docs[..].shuffle(&mut thread_rng());
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         for doc in docs {
             index_writer.add_document(doc);
         }
@@ -684,7 +680,7 @@ mod bench {
         // 40425 docs
         docs[..].shuffle(&mut thread_rng());
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         for doc in docs {
             index_writer.add_document(doc);
         }

src/collector/int_facet_collector.rs

@@ -89,7 +89,7 @@ mod tests {
         let index = Index::create_in_ram(schema.clone());
 
         {
-            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 0u64..10u64 {
                     index_writer.add_document(doc!(

src/collector/mod.rs

@@ -109,7 +109,6 @@ pub use self::tweak_score_top_collector::{ScoreSegmentTweaker, ScoreTweaker};
 
 mod facet_collector;
 pub use self::facet_collector::FacetCollector;
-use crate::query::Weight;
 
 /// `Fruit` is the type for the result of our collection.
 /// e.g. `usize` for the `Count` collector.
@@ -133,7 +132,7 @@ 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;
@@ -155,29 +154,6 @@ 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::Fruit>) -> crate::Result<Self::Fruit>;
-
-    /// Created a segment collector and
-    fn collect_segment(
-        &self,
-        weight: &dyn Weight,
-        segment_ord: u32,
-        reader: &SegmentReader,
-    ) -> crate::Result<<Self::Child as SegmentCollector>::Fruit> {
-        let mut segment_collector = self.for_segment(segment_ord as u32, reader)?;
-
-        if let Some(delete_bitset) = reader.delete_bitset() {
-            weight.for_each(reader, &mut |doc, score| {
-                if delete_bitset.is_alive(doc) {
-                    segment_collector.collect(doc, score);
-                }
-            })?;
-        } else {
-            weight.for_each(reader, &mut |doc, score| {
-                segment_collector.collect(doc, score);
-            })?;
-        }
-        Ok(segment_collector.harvest())
-    }
 }
 
 /// The `SegmentCollector` is the trait in charge of defining the

src/collector/multi_collector.rs

@@ -55,7 +55,7 @@ impl<TCollector: Collector> Collector for CollectorWrapper<TCollector> {
 impl SegmentCollector for Box<dyn BoxableSegmentCollector> {
     type Fruit = Box<dyn Fruit>;
 
-    fn collect(&mut self, doc: u32, score: Score) {
+    fn collect(&mut self, doc: u32, score: f32) {
         self.as_mut().collect(doc, score);
     }
 
@@ -65,7 +65,7 @@ impl SegmentCollector for Box<dyn BoxableSegmentCollector> {
 }
 
 pub trait BoxableSegmentCollector {
-    fn collect(&mut self, doc: u32, score: Score);
+    fn collect(&mut self, doc: u32, score: f32);
     fn harvest_from_box(self: Box<Self>) -> Box<dyn Fruit>;
 }
 
@@ -74,7 +74,7 @@ pub struct SegmentCollectorWrapper<TSegmentCollector: SegmentCollector>(TSegment
 impl<TSegmentCollector: SegmentCollector> BoxableSegmentCollector
     for SegmentCollectorWrapper<TSegmentCollector>
 {
-    fn collect(&mut self, doc: u32, score: Score) {
+    fn collect(&mut self, doc: u32, score: f32) {
         self.0.collect(doc, score);
     }
 
@@ -259,7 +259,7 @@ mod tests {
 
         let index = Index::create_in_ram(schema);
         {
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.add_document(doc!(text=>"abc"));
             index_writer.add_document(doc!(text=>"abc abc abc"));
             index_writer.add_document(doc!(text=>"abc abc"));

src/collector/tests.rs

@@ -206,7 +206,7 @@ impl Collector for BytesFastFieldTestCollector {
 impl SegmentCollector for BytesFastFieldSegmentCollector {
     type Fruit = Vec<u8>;
 
-    fn collect(&mut self, doc: u32, _score: Score) {
+    fn collect(&mut self, doc: u32, _score: f32) {
         let data = self.reader.get_bytes(doc);
         self.vals.extend(data);
     }

src/collector/top_collector.rs

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

src/collector/top_score_collector.rs

@@ -1,20 +1,18 @@
 use super::Collector;
 use crate::collector::custom_score_top_collector::CustomScoreTopCollector;
+use crate::collector::top_collector::TopCollector;
 use crate::collector::top_collector::TopSegmentCollector;
-use crate::collector::top_collector::{ComparableDoc, TopCollector};
 use crate::collector::tweak_score_top_collector::TweakedScoreTopCollector;
 use crate::collector::{
     CustomScorer, CustomSegmentScorer, ScoreSegmentTweaker, ScoreTweaker, SegmentCollector,
 };
 use crate::fastfield::FastFieldReader;
-use crate::query::Weight;
 use crate::schema::Field;
 use crate::DocAddress;
 use crate::DocId;
 use crate::Score;
 use crate::SegmentLocalId;
 use crate::SegmentReader;
-use std::collections::BinaryHeap;
 use std::fmt;
 
 /// The `TopDocs` collector keeps track of the top `K` documents
@@ -38,7 +36,7 @@ use std::fmt;
 /// 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"));
@@ -52,18 +50,14 @@ use std::fmt;
 /// let query = query_parser.parse_query("diary").unwrap();
 /// let top_docs = searcher.search(&query, &TopDocs::with_limit(2)).unwrap();
 ///
-/// assert_eq!(top_docs[0].1, DocAddress(0, 1));
-/// assert_eq!(top_docs[1].1, DocAddress(0, 3));
+/// assert_eq!(&top_docs[0], &(0.7261542, DocAddress(0, 1)));
+/// assert_eq!(&top_docs[1], &(0.6099695, DocAddress(0, 3)));
 /// ```
 pub struct TopDocs(TopCollector<Score>);
 
 impl fmt::Debug for TopDocs {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            f,
-            "TopDocs(limit={}, offset={})",
-            self.0.limit, self.0.offset
-        )
+        write!(f, "TopDocs({})", self.0.limit())
     }
 }
 
@@ -72,7 +66,7 @@ struct ScorerByFastFieldReader {
 }
 
 impl CustomSegmentScorer<u64> for ScorerByFastFieldReader {
-    fn score(&mut self, doc: DocId) -> u64 {
+    fn score(&self, doc: DocId) -> u64 {
         self.ff_reader.get_u64(u64::from(doc))
     }
 }
@@ -107,45 +101,6 @@ impl TopDocs {
         TopDocs(TopCollector::with_limit(limit))
     }
 
-    /// Skip the first "offset" documents when collecting.
-    ///
-    /// This is equivalent to `OFFSET` in MySQL or PostgreSQL and `start` in
-    /// Lucene's TopDocsCollector.
-    ///
-    /// ```rust
-    /// use tantivy::collector::TopDocs;
-    /// use tantivy::query::QueryParser;
-    /// use tantivy::schema::{Schema, TEXT};
-    /// use tantivy::{doc, DocAddress, Index};
-    ///
-    /// let mut schema_builder = Schema::builder();
-    /// let title = schema_builder.add_text_field("title", TEXT);
-    /// let schema = schema_builder.build();
-    /// let index = Index::create_in_ram(schema);
-    ///
-    /// let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
-    /// index_writer.add_document(doc!(title => "The Name of the Wind"));
-    /// index_writer.add_document(doc!(title => "The Diary of Muadib"));
-    /// index_writer.add_document(doc!(title => "A Dairy Cow"));
-    /// index_writer.add_document(doc!(title => "The Diary of a Young Girl"));
-    /// index_writer.add_document(doc!(title => "The Diary of Lena Mukhina"));
-    /// assert!(index_writer.commit().is_ok());
-    ///
-    /// let reader = index.reader().unwrap();
-    /// let searcher = reader.searcher();
-    ///
-    /// let query_parser = QueryParser::for_index(&index, vec![title]);
-    /// let query = query_parser.parse_query("diary").unwrap();
-    /// let top_docs = searcher.search(&query, &TopDocs::with_limit(2).and_offset(1)).unwrap();
-    ///
-    /// assert_eq!(top_docs.len(), 2);
-    /// assert_eq!(top_docs[0].1, DocAddress(0, 4));
-    /// assert_eq!(top_docs[1].1, DocAddress(0, 3));
-    /// ```
-    pub fn and_offset(self, offset: usize) -> TopDocs {
-        TopDocs(self.0.and_offset(offset))
-    }
-
     /// Set top-K to rank documents by a given fast field.
     ///
     /// ```rust
@@ -163,7 +118,7 @@ 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)?;
+    /// #   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));
@@ -264,7 +219,7 @@ impl TopDocs {
     /// fn create_index() -> tantivy::Result<Index> {
     ///   let schema = create_schema();
     ///   let index = Index::create_in_ram(schema);
-    ///   let mut index_writer = index.writer_with_num_threads(1, 10_000_000)?;
+    ///   let mut index_writer = index.writer_with_num_threads(1, 3_000_000)?;
     ///   let product_name = index.schema().get_field("product_name").unwrap();
     ///   let popularity: Field = index.schema().get_field("popularity").unwrap();
     ///   index_writer.add_document(doc!(product_name => "The Diary of Muadib", popularity => 1u64));
@@ -303,7 +258,7 @@ impl TopDocs {
     ///                 let popularity: u64 = popularity_reader.get(doc);
     ///                 // Well.. For the sake of the example we use a simple logarithm
     ///                 // function.
-    ///                 let popularity_boost_score = ((2u64 + popularity) as Score).log2();
+    ///                 let popularity_boost_score = ((2u64 + popularity) as f32).log2();
     ///                 popularity_boost_score * original_score
     ///             }
     ///           });
@@ -324,9 +279,9 @@ impl TopDocs {
     where
         TScore: 'static + Send + Sync + Clone + PartialOrd,
         TScoreSegmentTweaker: ScoreSegmentTweaker<TScore> + 'static,
-        TScoreTweaker: ScoreTweaker<TScore, Child = TScoreSegmentTweaker> + Send + Sync,
+        TScoreTweaker: ScoreTweaker<TScore, Child = TScoreSegmentTweaker>,
     {
-        TweakedScoreTopCollector::new(score_tweaker, self.0.into_tscore())
+        TweakedScoreTopCollector::new(score_tweaker, self.0.limit())
     }
 
     /// Ranks the documents using a custom score.
@@ -371,7 +326,7 @@ impl TopDocs {
     /// # fn main() -> tantivy::Result<()> {
     /// #   let schema = create_schema();
     /// #   let index = Index::create_in_ram(schema);
-    /// #   let mut index_writer = index.writer_with_num_threads(1, 10_000_000)?;
+    /// #   let mut index_writer = index.writer_with_num_threads(1, 3_000_000)?;
     /// #   let product_name = index.schema().get_field("product_name").unwrap();
     /// #   
     /// let popularity: Field = index.schema().get_field("popularity").unwrap();
@@ -438,9 +393,9 @@ impl TopDocs {
     where
         TScore: 'static + Send + Sync + Clone + PartialOrd,
         TCustomSegmentScorer: CustomSegmentScorer<TScore> + 'static,
-        TCustomScorer: CustomScorer<TScore, Child = TCustomSegmentScorer> + Send + Sync,
+        TCustomScorer: CustomScorer<TScore, Child = TCustomSegmentScorer>,
     {
-        CustomScoreTopCollector::new(custom_score, self.0.into_tscore())
+        CustomScoreTopCollector::new(custom_score, self.0.limit())
     }
 }
 
@@ -468,64 +423,6 @@ impl Collector for TopDocs {
     ) -> crate::Result<Self::Fruit> {
         self.0.merge_fruits(child_fruits)
     }
-
-    fn collect_segment(
-        &self,
-        weight: &dyn Weight,
-        segment_ord: u32,
-        reader: &SegmentReader,
-    ) -> crate::Result<<Self::Child as SegmentCollector>::Fruit> {
-        let heap_len = self.0.limit + self.0.offset;
-        let mut heap: BinaryHeap<ComparableDoc<Score, DocId>> = BinaryHeap::with_capacity(heap_len);
-
-        if let Some(delete_bitset) = reader.delete_bitset() {
-            let mut threshold = Score::MIN;
-            weight.for_each_pruning(threshold, reader, &mut |doc, score| {
-                if delete_bitset.is_deleted(doc) {
-                    return threshold;
-                }
-                let heap_item = ComparableDoc {
-                    feature: score,
-                    doc,
-                };
-                if heap.len() < heap_len {
-                    heap.push(heap_item);
-                    if heap.len() == heap_len {
-                        threshold = heap.peek().map(|el| el.feature).unwrap_or(Score::MIN);
-                    }
-                    return threshold;
-                }
-                *heap.peek_mut().unwrap() = heap_item;
-                threshold = heap.peek().map(|el| el.feature).unwrap_or(Score::MIN);
-                threshold
-            })?;
-        } else {
-            weight.for_each_pruning(Score::MIN, reader, &mut |doc, score| {
-                let heap_item = ComparableDoc {
-                    feature: score,
-                    doc,
-                };
-                if heap.len() < heap_len {
-                    heap.push(heap_item);
-                    // TODO the threshold is suboptimal for heap.len == heap_len
-                    if heap.len() == heap_len {
-                        return heap.peek().map(|el| el.feature).unwrap_or(Score::MIN);
-                    } else {
-                        return Score::MIN;
-                    }
-                }
-                *heap.peek_mut().unwrap() = heap_item;
-                heap.peek().map(|el| el.feature).unwrap_or(Score::MIN)
-            })?;
-        }
-
-        let fruit = heap
-            .into_sorted_vec()
-            .into_iter()
-            .map(|cid| (cid.feature, DocAddress(segment_ord, cid.doc)))
-            .collect();
-        Ok(fruit)
-    }
 }
 
 /// Segment Collector associated to `TopDocs`.
@@ -535,7 +432,7 @@ impl SegmentCollector for TopScoreSegmentCollector {
     type Fruit = Vec<(Score, DocAddress)>;
 
     fn collect(&mut self, doc: DocId, score: Score) {
-        self.0.collect(doc, score);
+        self.0.collect(doc, score)
     }
 
     fn harvest(self) -> Vec<(Score, DocAddress)> {
@@ -549,10 +446,10 @@ mod tests {
     use crate::collector::Collector;
     use crate::query::{AllQuery, Query, QueryParser};
     use crate::schema::{Field, Schema, FAST, STORED, TEXT};
+    use crate::DocAddress;
     use crate::Index;
     use crate::IndexWriter;
     use crate::Score;
-    use crate::{DocAddress, DocId, SegmentReader};
 
     fn make_index() -> Index {
         let mut schema_builder = Schema::builder();
@@ -561,7 +458,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
         {
             // writing the segment
-            let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             index_writer.add_document(doc!(text_field=>"Hello happy tax payer."));
             index_writer.add_document(doc!(text_field=>"Droopy says hello happy tax payer"));
             index_writer.add_document(doc!(text_field=>"I like Droopy"));
@@ -570,13 +467,6 @@ mod tests {
         index
     }
 
-    fn assert_results_equals(results: &[(Score, DocAddress)], expected: &[(Score, DocAddress)]) {
-        for (result, expected) in results.iter().zip(expected.iter()) {
-            assert_eq!(result.1, expected.1);
-            crate::assert_nearly_equals!(result.0, expected.0);
-        }
-    }
-
     #[test]
     fn test_top_collector_not_at_capacity() {
         let index = make_index();
@@ -589,31 +479,16 @@ mod tests {
             .searcher()
             .search(&text_query, &TopDocs::with_limit(4))
             .unwrap();
-        assert_results_equals(
-            &score_docs,
-            &[
+        assert_eq!(
+            score_docs,
+            vec![
                 (0.81221175, DocAddress(0u32, 1)),
                 (0.5376842, DocAddress(0u32, 2)),
-                (0.48527452, DocAddress(0, 0)),
-            ],
+                (0.48527452, DocAddress(0, 0))
+            ]
         );
     }
 
-    #[test]
-    fn test_top_collector_not_at_capacity_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let score_docs: Vec<(Score, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &TopDocs::with_limit(4).and_offset(2))
-            .unwrap();
-        assert_results_equals(&score_docs[..], &[(0.48527452, DocAddress(0, 0))]);
-    }
-
     #[test]
     fn test_top_collector_at_capacity() {
         let index = make_index();
@@ -626,33 +501,12 @@ mod tests {
             .searcher()
             .search(&text_query, &TopDocs::with_limit(2))
             .unwrap();
-        assert_results_equals(
-            &score_docs,
-            &[
+        assert_eq!(
+            score_docs,
+            vec![
                 (0.81221175, DocAddress(0u32, 1)),
                 (0.5376842, DocAddress(0u32, 2)),
-            ],
-        );
-    }
-
-    #[test]
-    fn test_top_collector_at_capacity_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let score_docs: Vec<(Score, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &TopDocs::with_limit(2).and_offset(1))
-            .unwrap();
-        assert_results_equals(
-            &score_docs[..],
-            &[
-                (0.5376842, DocAddress(0u32, 2)),
-                (0.48527452, DocAddress(0, 0)),
-            ],
+            ]
         );
     }
 
@@ -713,8 +567,8 @@ mod tests {
         let top_collector = TopDocs::with_limit(4).order_by_u64_field(size);
         let top_docs: Vec<(u64, DocAddress)> = searcher.search(&query, &top_collector).unwrap();
         assert_eq!(
-            &top_docs[..],
-            &[
+            top_docs,
+            vec![
                 (64, DocAddress(0, 1)),
                 (16, DocAddress(0, 2)),
                 (12, DocAddress(0, 0))
@@ -769,50 +623,6 @@ mod tests {
         }
     }
 
-    #[test]
-    fn test_tweak_score_top_collector_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let collector = TopDocs::with_limit(2).and_offset(1).tweak_score(
-            move |_segment_reader: &SegmentReader| move |doc: DocId, _original_score: Score| doc,
-        );
-        let score_docs: Vec<(u32, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &collector)
-            .unwrap();
-
-        assert_eq!(
-            score_docs,
-            vec![(1, DocAddress(0, 1)), (0, DocAddress(0, 0)),]
-        );
-    }
-
-    #[test]
-    fn test_custom_score_top_collector_with_offset() {
-        let index = make_index();
-        let field = index.schema().get_field("text").unwrap();
-        let query_parser = QueryParser::for_index(&index, vec![field]);
-        let text_query = query_parser.parse_query("droopy tax").unwrap();
-        let collector = TopDocs::with_limit(2)
-            .and_offset(1)
-            .custom_score(move |_segment_reader: &SegmentReader| move |doc: DocId| doc);
-        let score_docs: Vec<(u32, DocAddress)> = index
-            .reader()
-            .unwrap()
-            .searcher()
-            .search(&text_query, &collector)
-            .unwrap();
-
-        assert_eq!(
-            score_docs,
-            vec![(1, DocAddress(0, 1)), (0, DocAddress(0, 0)),]
-        );
-    }
-
     fn index(
         query: &str,
         query_field: Field,
@@ -821,7 +631,7 @@ mod tests {
     ) -> (Index, Box<dyn Query>) {
         let index = Index::create_in_ram(schema);
 
-        let mut index_writer = index.writer_with_num_threads(1, 10_000_000).unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         doc_adder(&mut index_writer);
         index_writer.commit().unwrap();
         let query_parser = QueryParser::for_index(&index, vec![query_field]);

src/collector/tweak_score_top_collector.rs

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

src/common/bitset.rs

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

src/common/composite_file.rs

@@ -190,11 +190,12 @@ mod test {
     use crate::schema::Field;
     use std::io::Write;
     use std::path::Path;
+    
 
     #[test]
     fn test_composite_file() {
         let path = Path::new("test_path");
-        let mut directory = RAMDirectory::create();
+        let mut directory = RAMDirectory::default();
         {
             let w = directory.open_write(path).unwrap();
             let mut composite_write = CompositeWrite::wrap(w);

src/common/mod.rs

@@ -2,6 +2,7 @@ pub mod bitpacker;
 mod bitset;
 mod composite_file;
 mod counting_writer;
+mod mutable_enum;
 mod serialize;
 mod vint;
 
@@ -9,10 +10,9 @@ pub use self::bitset::BitSet;
 pub(crate) use self::bitset::TinySet;
 pub(crate) use self::composite_file::{CompositeFile, CompositeWrite};
 pub use self::counting_writer::CountingWriter;
+pub(crate) use self::mutable_enum::MutableEnum;
 pub use self::serialize::{BinarySerializable, FixedSize};
-pub use self::vint::{
-    read_u32_vint, read_u32_vint_no_advance, serialize_vint_u32, write_u32_vint, VInt,
-};
+pub use self::vint::{read_u32_vint, serialize_vint_u32, write_u32_vint, VInt};
 pub use byteorder::LittleEndian as Endianness;
 
 /// Segment's max doc must be `< MAX_DOC_LIMIT`.

src/common/mutable_enum.rs

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

src/common/serialize.rs

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

src/common/vint.rs

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

src/core/executor.rs

@@ -1,6 +1,5 @@
 use crossbeam::channel;
 use rayon::{ThreadPool, ThreadPoolBuilder};
-use slog::{error, Logger};
 
 /// Search executor whether search request are single thread or multithread.
 ///
@@ -44,7 +43,6 @@ impl Executor {
         &self,
         f: F,
         args: AIterator,
-        logger: Logger,
     ) -> crate::Result<Vec<R>> {
         match self {
             Executor::SingleThread => args.map(f).collect::<crate::Result<_>>(),
@@ -59,7 +57,7 @@ impl Executor {
                                 let (idx, arg) = arg_with_idx;
                                 let fruit = f(arg);
                                 if let Err(err) = fruit_sender.send((idx, fruit)) {
-                                    error!(logger, "Failed to send search task. It probably means all search threads have panicked. {:?}", err);
+                                    error!("Failed to send search task. It probably means all search threads have panicked. {:?}", err);
                                 }
                             });
                         }
@@ -89,21 +87,17 @@ impl Executor {
 #[cfg(test)]
 mod tests {
 
-    use slog::{o, Discard, Logger};
-
     use super::Executor;
 
     #[test]
     #[should_panic(expected = "panic should propagate")]
     fn test_panic_propagates_single_thread() {
-        let logger = Logger::root(Discard, o!());
         let _result: Vec<usize> = Executor::single_thread()
             .map(
                 |_| {
                     panic!("panic should propagate");
                 },
                 vec![0].into_iter(),
-                logger,
             )
             .unwrap();
     }
@@ -111,7 +105,6 @@ mod tests {
     #[test]
     #[should_panic] //< unfortunately the panic message is not propagated
     fn test_panic_propagates_multi_thread() {
-        let logger = Logger::root(Discard, o!());
         let _result: Vec<usize> = Executor::multi_thread(1, "search-test")
             .unwrap()
             .map(
@@ -119,16 +112,14 @@ mod tests {
                     panic!("panic should propagate");
                 },
                 vec![0].into_iter(),
-                logger,
             )
             .unwrap();
     }
 
     #[test]
     fn test_map_singlethread() {
-        let logger = Logger::root(Discard, o!());
         let result: Vec<usize> = Executor::single_thread()
-            .map(|i| Ok(i * 2), 0..1_000, logger)
+            .map(|i| Ok(i * 2), 0..1_000)
             .unwrap();
         assert_eq!(result.len(), 1_000);
         for i in 0..1_000 {
@@ -138,10 +129,9 @@ mod tests {
 
     #[test]
     fn test_map_multithread() {
-        let logger = Logger::root(Discard, o!());
         let result: Vec<usize> = Executor::multi_thread(3, "search-test")
             .unwrap()
-            .map(|i| Ok(i * 2), 0..10, logger)
+            .map(|i| Ok(i * 2), 0..10)
             .unwrap();
         assert_eq!(result.len(), 10);
         for i in 0..10 {

src/core/index.rs

@@ -12,8 +12,8 @@ use crate::directory::INDEX_WRITER_LOCK;
 use crate::directory::{Directory, RAMDirectory};
 use crate::error::DataCorruption;
 use crate::error::TantivyError;
-use crate::indexer::index_writer::HEAP_SIZE_MIN;
 use crate::indexer::segment_updater::save_new_metas;
+use crate::indexer::IndexWriterConfig;
 use crate::reader::IndexReader;
 use crate::reader::IndexReaderBuilder;
 use crate::schema::Field;
@@ -21,14 +21,12 @@ use crate::schema::FieldType;
 use crate::schema::Schema;
 use crate::tokenizer::{TextAnalyzer, TokenizerManager};
 use crate::IndexWriter;
-use slog::Logger;
+use num_cpus;
 use std::borrow::BorrowMut;
 use std::collections::HashSet;
 use std::fmt;
-
 #[cfg(feature = "mmap")]
-use std::path::Path;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
 fn load_metas(
@@ -58,14 +56,7 @@ pub struct Index {
 }
 
 impl Index {
-
-    pub(crate) fn logger(&self) -> &Logger {
-        self.directory.logger()
-    }
-
-    /// Examines the directory to see if it contains an index.
-    ///
-    /// Effectively, it only checks for the presence of the `meta.json` file.
+    /// Examines the director to see if it contains an index
     pub fn exists<Dir: Directory>(dir: &Dir) -> bool {
         dir.exists(&META_FILEPATH)
     }
@@ -148,18 +139,16 @@ 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::new_from_directory(directory, schema)
+        Index::from_directory(directory, schema)
     }
 
     /// Create a new index from a directory.
     ///
     /// This will overwrite existing meta.json
-    fn new_from_directory(mut directory: ManagedDirectory, schema: Schema) -> crate::Result<Index> {
+    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())
@@ -250,8 +239,6 @@ impl Index {
 
     /// Open the index using the provided directory
     pub fn open<D: Directory>(directory: D) -> crate::Result<Index> {
-        let logger: &Logger = directory.logger();
-        slog::info!(logger, "index-open"; "directory" => format!("{:?}", directory));
         let directory = ManagedDirectory::wrap(directory)?;
         let inventory = SegmentMetaInventory::default();
         let metas = load_metas(&directory, &inventory)?;
@@ -286,8 +273,40 @@ impl Index {
     pub fn writer_with_num_threads(
         &self,
         num_threads: usize,
-        overall_heap_size_in_bytes: usize,
+        overall_heap_size_in_bytes: u64,
     ) -> crate::Result<IndexWriter> {
+        let config = IndexWriterConfig {
+            max_indexing_threads: num_threads,
+            memory_budget: overall_heap_size_in_bytes,
+            ..Default::default()
+        };
+        self.writer_from_config(config)
+    }
+
+    /// Creates a multithreaded writer
+    ///
+    /// Tantivy will automatically define the number of threads to use.
+    /// `overall_heap_size_in_bytes` is the total target memory usage that will be split
+    /// between a given number of threads.
+    ///
+    /// # Errors
+    /// If the lockfile already exists, returns `Error::FileAlreadyExists`.
+    /// # Panics
+    /// If the heap size per thread is too small, panics.
+    pub fn writer(&self, overall_heap_size_in_bytes: u64) -> crate::Result<IndexWriter> {
+        let config = IndexWriterConfig {
+            max_indexing_threads: num_cpus::get(),
+            memory_budget: overall_heap_size_in_bytes,
+            ..Default::default()
+        };
+        self.writer_from_config(config)
+    }
+
+    /// Creates a new writer with a given configuration.
+    ///
+    /// See [`IndexWriterConfig`](./struct.IndexWriterConfig.html) for more information.
+    pub fn writer_from_config(&self, mut config: IndexWriterConfig) -> crate::Result<IndexWriter> {
+        config.validate()?;
         let directory_lock = self
             .directory
             .acquire_lock(&INDEX_WRITER_LOCK)
@@ -303,41 +322,7 @@ impl Index {
                     ),
                 )
             })?;
-        let heap_size_in_bytes_per_thread = overall_heap_size_in_bytes / num_threads;
-        IndexWriter::new(
-            self,
-            num_threads,
-            heap_size_in_bytes_per_thread,
-            directory_lock,
-        )
-    }
-
-    /// Helper to create an index writer for tests.
-    ///
-    /// That index writer only simply has a single thread and a heap of 5 MB.
-    /// Using a single thread gives us a deterministic allocation of DocId.
-    #[cfg(test)]
-    pub fn writer_for_tests(&self) -> crate::Result<IndexWriter> {
-        self.writer_with_num_threads(1, 10_000_000)
-    }
-
-    /// Creates a multithreaded writer
-    ///
-    /// Tantivy will automatically define the number of threads to use.
-    /// `overall_heap_size_in_bytes` is the total target memory usage that will be split
-    /// between a given number of threads.
-    ///
-    /// # Errors
-    /// If the lockfile already exists, returns `Error::FileAlreadyExists`.
-    /// # Panics
-    /// If the heap size per thread is too small, panics.
-    pub fn writer(&self, overall_heap_size_in_bytes: usize) -> crate::Result<IndexWriter> {
-        let mut num_threads = num_cpus::get();
-        let heap_size_in_bytes_per_thread = overall_heap_size_in_bytes / num_threads;
-        if heap_size_in_bytes_per_thread < HEAP_SIZE_MIN {
-            num_threads = (overall_heap_size_in_bytes / HEAP_SIZE_MIN).max(1);
-        }
-        self.writer_with_num_threads(num_threads, overall_heap_size_in_bytes)
+        IndexWriter::new(self, config, directory_lock)
     }
 
     /// Accessor to the index schema
@@ -491,7 +476,7 @@ mod tests {
             .try_into()
             .unwrap();
         assert_eq!(reader.searcher().num_docs(), 0);
-        test_index_on_commit_reload_policy_aux(field, &index, &reader);
+        test_index_on_commit_reload_policy_aux(field, index.clone(), &index, &reader);
     }
 
     #[cfg(feature = "mmap")]
@@ -515,7 +500,7 @@ mod tests {
                 .try_into()
                 .unwrap();
             assert_eq!(reader.searcher().num_docs(), 0);
-            test_index_on_commit_reload_policy_aux(field, &index, &reader);
+            test_index_on_commit_reload_policy_aux(field, index.clone(), &index, &reader);
         }
 
         #[test]
@@ -523,7 +508,7 @@ mod tests {
             let schema = throw_away_schema();
             let field = schema.get_field("num_likes").unwrap();
             let mut index = Index::create_from_tempdir(schema).unwrap();
-            let mut writer = index.writer_for_tests().unwrap();
+            let mut writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             writer.commit().unwrap();
             let reader = index
                 .reader_builder()
@@ -557,36 +542,30 @@ mod tests {
                 .try_into()
                 .unwrap();
             assert_eq!(reader.searcher().num_docs(), 0);
-            test_index_on_commit_reload_policy_aux(field, &write_index, &reader);
+            test_index_on_commit_reload_policy_aux(field, read_index, &write_index, &reader);
         }
     }
-    fn test_index_on_commit_reload_policy_aux(field: Field, index: &Index, reader: &IndexReader) {
-        let mut reader_index = reader.index();
+
+    fn test_index_on_commit_reload_policy_aux(
+        field: Field,
+        mut reader_index: Index,
+        index: &Index,
+        reader: &IndexReader,
+    ) {
         let (sender, receiver) = crossbeam::channel::unbounded();
         let _watch_handle = reader_index.directory_mut().watch(Box::new(move || {
             let _ = sender.send(());
         }));
-        let mut writer = index.writer_for_tests().unwrap();
+        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

src/core/index_meta.rs

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

src/core/inverted_index_reader.rs

@@ -3,9 +3,11 @@ use crate::directory::ReadOnlySource;
 use crate::positions::PositionReader;
 use crate::postings::TermInfo;
 use crate::postings::{BlockSegmentPostings, SegmentPostings};
+use crate::schema::FieldType;
 use crate::schema::IndexRecordOption;
 use crate::schema::Term;
 use crate::termdict::TermDictionary;
+use owned_read::OwnedRead;
 
 /// The inverted index reader is in charge of accessing
 /// the inverted index associated to a specific field.
@@ -53,7 +55,10 @@ impl InvertedIndexReader {
 
     /// 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_source: ReadOnlySource::empty(),
@@ -92,7 +97,8 @@ impl InvertedIndexReader {
         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);
+        let postings_reader = OwnedRead::new(postings_slice);
+        block_postings.reset(term_info.doc_freq, postings_reader);
     }
 
     /// Returns a block postings given a `Term`.
@@ -121,7 +127,7 @@ impl InvertedIndexReader {
         let postings_data = self.postings_source.slice_from(offset);
         BlockSegmentPostings::from_data(
             term_info.doc_freq,
-            postings_data,
+            OwnedRead::new(postings_data),
             self.record_option,
             requested_option,
         )

src/core/searcher.rs

@@ -1,8 +1,11 @@
 use crate::collector::Collector;
+use crate::collector::SegmentCollector;
 use crate::core::Executor;
 use crate::core::InvertedIndexReader;
 use crate::core::SegmentReader;
 use crate::query::Query;
+use crate::query::Scorer;
+use crate::query::Weight;
 use crate::schema::Document;
 use crate::schema::Schema;
 use crate::schema::{Field, Term};
@@ -14,6 +17,26 @@ use crate::Index;
 use std::fmt;
 use std::sync::Arc;
 
+fn collect_segment<C: Collector>(
+    collector: &C,
+    weight: &dyn Weight,
+    segment_ord: u32,
+    segment_reader: &SegmentReader,
+) -> crate::Result<C::Fruit> {
+    let mut scorer = weight.scorer(segment_reader, 1.0f32)?;
+    let mut segment_collector = collector.for_segment(segment_ord as u32, segment_reader)?;
+    if let Some(delete_bitset) = segment_reader.delete_bitset() {
+        scorer.for_each(&mut |doc, score| {
+            if delete_bitset.is_alive(doc) {
+                segment_collector.collect(doc, score);
+            }
+        });
+    } else {
+        scorer.for_each(&mut |doc, score| segment_collector.collect(doc, score));
+    }
+    Ok(segment_collector.harvest())
+}
+
 /// Holds a list of `SegmentReader`s ready for search.
 ///
 /// It guarantees that the `Segment` will not be removed before
@@ -140,10 +163,14 @@ impl Searcher {
         let segment_readers = self.segment_readers();
         let fruits = executor.map(
             |(segment_ord, segment_reader)| {
-                collector.collect_segment(weight.as_ref(), segment_ord as u32, segment_reader)
+                collect_segment(
+                    collector,
+                    weight.as_ref(),
+                    segment_ord as u32,
+                    segment_reader,
+                )
             },
             segment_readers.iter().enumerate(),
-            self.index.logger().clone(),
         )?;
         collector.merge_fruits(fruits)
     }

src/core/segment.rs

@@ -3,41 +3,140 @@ use crate::core::Index;
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::directory::error::{OpenReadError, OpenWriteError};
-use crate::directory::Directory;
+use crate::directory::{Directory, ManagedDirectory, RAMDirectory};
 use crate::directory::{ReadOnlySource, WritePtr};
 use crate::indexer::segment_serializer::SegmentSerializer;
 use crate::schema::Schema;
 use crate::Opstamp;
 use std::fmt;
+use std::ops::{Deref, DerefMut};
 use std::path::PathBuf;
+use crate::indexer::{ResourceManager};
+
+#[derive(Clone)]
+pub(crate) enum SegmentDirectory {
+    Persisted(ManagedDirectory),
+    Volatile {
+        directory: RAMDirectory,
+    },
+}
+
+impl SegmentDirectory {
+    fn new_volatile(memory_manager: ResourceManager) -> SegmentDirectory {
+        SegmentDirectory::Volatile {
+            directory: RAMDirectory::create_with_memory_manager(memory_manager),
+        }
+    }
+}
+
+impl fmt::Debug for SegmentDirectory {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            SegmentDirectory::Volatile { .. } => write!(f, "volatile")?,
+            SegmentDirectory::Persisted(dir) => write!(f, "Persisted({:?})", dir)?,
+        }
+        Ok(())
+    }
+}
+
+impl From<ManagedDirectory> for SegmentDirectory {
+    fn from(directory: ManagedDirectory) -> Self {
+        SegmentDirectory::Persisted(directory)
+    }
+}
+
+impl Deref for SegmentDirectory {
+    type Target = dyn Directory;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            SegmentDirectory::Volatile {
+                directory, ..
+            } => directory,
+            SegmentDirectory::Persisted(dir) => dir,
+        }
+    }
+}
+
+impl DerefMut for SegmentDirectory {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        match self {
+            SegmentDirectory::Volatile { directory, .. } => directory,
+            SegmentDirectory::Persisted(dir) => dir,
+        }
+    }
+}
 
 /// A segment is a piece of the index.
 #[derive(Clone)]
 pub struct Segment {
-    index: Index,
+    schema: Schema,
     meta: SegmentMeta,
+    directory: SegmentDirectory,
 }
 
 impl fmt::Debug for Segment {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "Segment({:?})", self.id().uuid_string())
+        write!(
+            f,
+            "Segment(id={:?}, directory={:?})",
+            self.id().uuid_string(),
+            self.directory
+        )
     }
 }
 
 impl Segment {
-    /// Creates a new segment given an `Index` and a `SegmentId`
-    pub(crate) fn for_index(index: Index, meta: SegmentMeta) -> Segment {
-        Segment { index, meta }
+    pub(crate) fn new_persisted(
+        meta: SegmentMeta,
+        directory: ManagedDirectory,
+        schema: Schema,
+    ) -> Segment {
+        Segment {
+            meta,
+            schema,
+            directory: SegmentDirectory::from(directory),
+        }
     }
 
-    /// Returns the index the segment belongs to.
-    pub fn index(&self) -> &Index {
-        &self.index
+    /// Creates a new segment that embeds its own `RAMDirectory`.
+    ///
+    /// That segment is entirely dissociated from the index directory.
+    /// It will be persisted by a background thread in charge of IO.
+    pub fn new_volatile(meta: SegmentMeta, schema: Schema, resource_manager: ResourceManager) -> Segment {
+        Segment {
+            schema,
+            meta,
+            directory: SegmentDirectory::new_volatile(resource_manager),
+        }
+    }
+
+    /// Creates a new segment given an `Index` and a `SegmentId`
+    pub(crate) fn for_index(index: Index, meta: SegmentMeta) -> Segment {
+        let segment_directory = index.directory().clone();
+        Segment::new_persisted(meta, segment_directory, index.schema())
+    }
+
+    /// Persists a given `Segment` to a directory.
+    pub fn persist(&mut self, mut dest_directory: ManagedDirectory) -> crate::Result<()> {
+        if let SegmentDirectory::Persisted(_) = self.directory {
+            // this segment is already persisted.
+            return Ok(());
+        }
+        if let SegmentDirectory::Volatile { directory, ..} = &self.directory {
+            directory.persist(&mut dest_directory)?;
+        }
+        self.directory = SegmentDirectory::Persisted(dest_directory);
+        Ok(())
+    }
+
+    pub fn into_volatile(&self, memory_manager: ResourceManager) -> Segment {
+        Segment::new_volatile(self.meta.clone(), self.schema.clone(), memory_manager)
     }
 
     /// Returns our index's schema.
     pub fn schema(&self) -> Schema {
-        self.index.schema()
+        self.schema.clone()
     }
 
     /// Returns the segment meta-information
@@ -51,16 +150,18 @@ impl Segment {
     /// as we finalize a fresh new segment.
     pub(crate) fn with_max_doc(self, max_doc: u32) -> Segment {
         Segment {
-            index: self.index,
+            schema: self.schema,
             meta: self.meta.with_max_doc(max_doc),
+            directory: self.directory,
         }
     }
 
     #[doc(hidden)]
     pub fn with_delete_meta(self, num_deleted_docs: u32, opstamp: Opstamp) -> Segment {
         Segment {
-            index: self.index,
+            schema: self.schema,
             meta: self.meta.with_delete_meta(num_deleted_docs, opstamp),
+            directory: self.directory,
         }
     }
 
@@ -80,15 +181,15 @@ impl Segment {
     /// Open one of the component file for a *regular* read.
     pub fn open_read(&self, component: SegmentComponent) -> Result<ReadOnlySource, OpenReadError> {
         let path = self.relative_path(component);
-        let source = self.index.directory().open_read(&path)?;
+        let source = self.directory.open_read(&path)?;
         Ok(source)
     }
 
     /// Open one of the component file for *regular* write.
     pub fn open_write(&mut self, component: SegmentComponent) -> Result<WritePtr, OpenWriteError> {
         let path = self.relative_path(component);
-        let write = self.index.directory_mut().open_write(&path)?;
-        Ok(write)
+        let wrt = self.directory.open_write(&path)?;
+        Ok(wrt)
     }
 }
 

src/core/segment_id.rs

@@ -21,12 +21,6 @@ use std::sync::atomic;
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
 pub struct SegmentId(Uuid);
 
-impl ToString for SegmentId {
-    fn to_string(&self) -> String {
-        self.short_uuid_string()
-    }
-}
-
 #[cfg(test)]
 static AUTO_INC_COUNTER: Lazy<atomic::AtomicUsize> = Lazy::new(|| atomic::AtomicUsize::default());
 

src/core/segment_reader.rs

@@ -8,16 +8,15 @@ use crate::directory::ReadOnlySource;
 use crate::fastfield::DeleteBitSet;
 use crate::fastfield::FacetReader;
 use crate::fastfield::FastFieldReaders;
-use crate::fieldnorm::{FieldNormReader, FieldNormReaders};
+use crate::fieldnorm::FieldNormReader;
+use crate::schema::Field;
 use crate::schema::FieldType;
 use crate::schema::Schema;
-use crate::schema::{Field, IndexRecordOption};
 use crate::space_usage::SegmentSpaceUsage;
 use crate::store::StoreReader;
 use crate::termdict::TermDictionary;
 use crate::DocId;
 use fail::fail_point;
-use slog::{warn, Logger};
 use std::collections::HashMap;
 use std::fmt;
 use std::sync::Arc;
@@ -49,12 +48,11 @@ pub struct SegmentReader {
     positions_composite: CompositeFile,
     positions_idx_composite: CompositeFile,
     fast_fields_readers: Arc<FastFieldReaders>,
-    fieldnorm_readers: FieldNormReaders,
+    fieldnorms_composite: CompositeFile,
 
     store_source: ReadOnlySource,
     delete_bitset_opt: Option<DeleteBitSet>,
     schema: Schema,
-    logger: Logger,
 }
 
 impl SegmentReader {
@@ -127,15 +125,17 @@ 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_source) = self.fieldnorms_composite.open_read(field) {
+            FieldNormReader::open(fieldnorm_source)
+        } else {
             let field_name = self.schema.get_field_name(field);
             let err_msg = format!(
                 "Field norm not found for field {:?}. Was it market as indexed during indexing.",
                 field_name
             );
-            crate::TantivyError::SchemaError(err_msg)
-        })
+            panic!(err_msg);
+        }
     }
 
     /// Accessor to the segment's `StoreReader`.
@@ -178,8 +178,8 @@ impl SegmentReader {
         let fast_field_readers =
             Arc::new(FastFieldReaders::load_all(&schema, &fast_fields_composite)?);
 
-        let fieldnorm_data = segment.open_read(SegmentComponent::FIELDNORMS)?;
-        let fieldnorm_readers = FieldNormReaders::open(fieldnorm_data)?;
+        let fieldnorms_data = segment.open_read(SegmentComponent::FIELDNORMS)?;
+        let fieldnorms_composite = CompositeFile::open(&fieldnorms_data)?;
 
         let delete_bitset_opt = if segment.meta().has_deletes() {
             let delete_data = segment.open_read(SegmentComponent::DELETE)?;
@@ -195,14 +195,13 @@ impl SegmentReader {
             termdict_composite,
             postings_composite,
             fast_fields_readers: fast_field_readers,
-            fieldnorm_readers,
+            fieldnorms_composite,
             segment_id: segment.id(),
             store_source,
             delete_bitset_opt,
             positions_composite,
             positions_idx_composite,
             schema,
-            logger: segment.index().logger().clone(),
         })
     }
 
@@ -213,11 +212,6 @@ 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) -> Arc<InvertedIndexReader> {
         if let Some(inv_idx_reader) = self
             .inv_idx_reader_cache
@@ -232,25 +226,21 @@ impl SegmentReader {
         let record_option_opt = field_type.get_index_record_option();
 
         if record_option_opt.is_none() {
-            warn!(
-                self.logger,
-                "Field {:?} does not seem indexed.",
-                field_entry.name()
-            );
+            panic!("Field {:?} does not seem indexed.", field_entry.name());
         }
 
+        let record_option = record_option_opt.unwrap();
+
         let postings_source_opt = self.postings_composite.open_read(field);
 
-        if postings_source_opt.is_none() || record_option_opt.is_none() {
+        if postings_source_opt.is_none() {
             // no documents in the segment contained this field.
             // As a result, no data is associated to the inverted index.
             //
             // Returns an empty inverted index.
-            let record_option = record_option_opt.unwrap_or(IndexRecordOption::Basic);
-            return Arc::new(InvertedIndexReader::empty(record_option));
+            return Arc::new(InvertedIndexReader::empty(field_type));
         }
 
-        let record_option = record_option_opt.unwrap();
         let postings_source = postings_source_opt.unwrap();
 
         let termdict_source = self.termdict_composite.open_read(field).expect(
@@ -305,8 +295,8 @@ impl SegmentReader {
     }
 
     /// Returns an iterator that will iterate over the alive document ids
-    pub fn doc_ids_alive<'a>(&'a self) -> impl Iterator<Item = DocId> + 'a {
-        (0u32..self.max_doc).filter(move |doc| !self.is_deleted(*doc))
+    pub fn doc_ids_alive(&self) -> SegmentReaderAliveDocsIterator<'_> {
+        SegmentReaderAliveDocsIterator::new(&self)
     }
 
     /// Summarize total space usage of this segment.
@@ -318,7 +308,7 @@ impl SegmentReader {
             self.positions_composite.space_usage(),
             self.positions_idx_composite.space_usage(),
             self.fast_fields_readers.space_usage(),
-            self.fieldnorm_readers.space_usage(),
+            self.fieldnorms_composite.space_usage(),
             self.get_store_reader().space_usage(),
             self.delete_bitset_opt
                 .as_ref()
@@ -334,6 +324,52 @@ impl fmt::Debug for SegmentReader {
     }
 }
 
+/// Implements the iterator trait to allow easy iteration
+/// over non-deleted ("alive") DocIds in a SegmentReader
+pub struct SegmentReaderAliveDocsIterator<'a> {
+    reader: &'a SegmentReader,
+    max_doc: DocId,
+    current: DocId,
+}
+
+impl<'a> SegmentReaderAliveDocsIterator<'a> {
+    pub fn new(reader: &'a SegmentReader) -> SegmentReaderAliveDocsIterator<'a> {
+        SegmentReaderAliveDocsIterator {
+            reader,
+            max_doc: reader.max_doc(),
+            current: 0,
+        }
+    }
+}
+
+impl<'a> Iterator for SegmentReaderAliveDocsIterator<'a> {
+    type Item = DocId;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // TODO: Use TinySet (like in BitSetDocSet) to speed this process up
+        if self.current >= self.max_doc {
+            return None;
+        }
+
+        // find the next alive doc id
+        while self.reader.is_deleted(self.current) {
+            self.current += 1;
+
+            if self.current >= self.max_doc {
+                return None;
+            }
+        }
+
+        // capture the current alive DocId
+        let result = Some(self.current);
+
+        // move down the chain
+        self.current += 1;
+
+        result
+    }
+}
+
 #[cfg(test)]
 mod test {
     use crate::core::Index;
@@ -349,7 +385,7 @@ mod test {
         let name = schema.get_field("name").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.add_document(doc!(name => "tantivy"));
             index_writer.add_document(doc!(name => "horse"));
             index_writer.add_document(doc!(name => "jockey"));

src/directory/directory.rs

@@ -1,5 +1,3 @@
-use slog::{error, Logger};
-
 use crate::directory::directory_lock::Lock;
 use crate::directory::error::LockError;
 use crate::directory::error::{DeleteError, OpenReadError, OpenWriteError};
@@ -66,10 +64,7 @@ impl<T: Send + Sync + 'static> From<Box<T>> for DirectoryLock {
 impl Drop for DirectoryLockGuard {
     fn drop(&mut self) {
         if let Err(e) = self.directory.delete(&*self.path) {
-            error!(
-                self.directory.logger(),
-                "Failed to remove the lock file. {:?}", e
-            );
+            error!("Failed to remove the lock file. {:?}", e);
         }
     }
 }
@@ -85,7 +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 {
@@ -214,9 +209,6 @@ pub trait Directory: DirectoryClone + fmt::Debug + Send + Sync + 'static {
     /// `OnCommit` `ReloadPolicy`. Not implementing watch in a `Directory` only prevents the
     /// `OnCommit` `ReloadPolicy` to work properly.
     fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle>;
-
-    /// Returns the `slog::Logger` configured for the `Directory`.
-    fn logger(&self) -> &Logger;
 }
 
 /// DirectoryClone

src/directory/error.rs

@@ -1,60 +1,160 @@
 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 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
@@ -117,41 +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),
-}
-
-/// 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 {
@@ -159,3 +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/footer.rs

@@ -94,24 +94,12 @@ impl Footer {
         match &self.versioned_footer {
             VersionedFooter::V1 {
                 crc32: _crc,
-                store_compression,
+                store_compression: compression,
             } => {
-                if &library_version.store_compression != store_compression {
+                if &library_version.store_compression != compression {
                     return Err(Incompatibility::CompressionMismatch {
                         library_compression_format: library_version.store_compression.to_string(),
-                        index_compression_format: store_compression.to_string(),
-                    });
-                }
-                Ok(())
-            }
-            VersionedFooter::V2 {
-                crc32: _crc,
-                store_compression,
-            } => {
-                if &library_version.store_compression != store_compression {
-                    return Err(Incompatibility::CompressionMismatch {
-                        library_compression_format: library_version.store_compression.to_string(),
-                        index_compression_format: store_compression.to_string(),
+                        index_compression_format: compression.to_string(),
                     });
                 }
                 Ok(())
@@ -132,29 +120,24 @@ pub enum VersionedFooter {
         crc32: CrcHashU32,
         store_compression: String,
     },
-    // Introduction of the Block WAND information.
-    V2 {
-        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::V2 {
+            VersionedFooter::V1 {
                 crc32,
                 store_compression: compression,
             } => {
                 // Serializes a valid `VersionedFooter` or panics if the version is unknown
                 // [   version    |   crc_hash  | compression_mode ]
                 // [    0..4      |     4..8    |     variable     ]
-                BinarySerializable::serialize(&2u32, &mut buf)?;
+                BinarySerializable::serialize(&1u32, &mut buf)?;
                 BinarySerializable::serialize(crc32, &mut buf)?;
                 BinarySerializable::serialize(compression, &mut buf)?;
             }
-            VersionedFooter::V1 { .. } | VersionedFooter::UnknownVersion => {
+            VersionedFooter::UnknownVersion => {
                 return Err(io::Error::new(
                     io::ErrorKind::InvalidInput,
                     "Cannot serialize an unknown versioned footer ",
@@ -183,30 +166,22 @@ impl BinarySerializable for VersionedFooter {
         reader.read_exact(&mut buf[..])?;
         let mut cursor = &buf[..];
         let version = u32::deserialize(&mut cursor)?;
-        if version != 1 && version != 2 {
-            return Ok(VersionedFooter::UnknownVersion);
-        }
-        let crc32 = u32::deserialize(&mut cursor)?;
-        let store_compression = String::deserialize(&mut cursor)?;
-        Ok(if version == 1 {
-            VersionedFooter::V1 {
+        if version == 1 {
+            let crc32 = u32::deserialize(&mut cursor)?;
+            let compression = String::deserialize(&mut cursor)?;
+            Ok(VersionedFooter::V1 {
                 crc32,
-                store_compression,
-            }
+                store_compression: compression,
+            })
         } else {
-            assert_eq!(version, 2);
-            VersionedFooter::V2 {
-                crc32,
-                store_compression,
-            }
-        })
+            Ok(VersionedFooter::UnknownVersion)
+        }
     }
 }
 
 impl VersionedFooter {
     pub fn crc(&self) -> Option<CrcHashU32> {
         match self {
-            VersionedFooter::V2 { crc32, .. } => Some(*crc32),
             VersionedFooter::V1 { crc32, .. } => Some(*crc32),
             VersionedFooter::UnknownVersion { .. } => None,
         }
@@ -244,7 +219,7 @@ impl<W: TerminatingWrite> Write for FooterProxy<W> {
 impl<W: TerminatingWrite> TerminatingWrite for FooterProxy<W> {
     fn terminate_ref(&mut self, _: AntiCallToken) -> io::Result<()> {
         let crc32 = self.hasher.take().unwrap().finalize();
-        let footer = Footer::new(VersionedFooter::V2 {
+        let footer = Footer::new(VersionedFooter::V1 {
             crc32,
             store_compression: crate::store::COMPRESSION.to_string(),
         });
@@ -271,17 +246,17 @@ mod tests {
         let mut vec = Vec::new();
         let footer_proxy = FooterProxy::new(&mut vec);
         assert!(footer_proxy.terminate().is_ok());
-        if crate::store::COMPRESSION == "lz4" {
-            assert_eq!(vec.len(), 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::V2 { store_compression, .. }
-           if store_compression == crate::store::COMPRESSION
-        ));
+        if let VersionedFooter::V1 {
+            crc32: _,
+            store_compression,
+        } = footer.versioned_footer
+        {
+            assert_eq!(store_compression, crate::store::COMPRESSION);
+        } else {
+            panic!("Versioned footer should be V1.");
+        }
         assert_eq!(&footer.version, crate::version());
     }
 
@@ -289,7 +264,7 @@ mod tests {
     fn test_serialize_deserialize_footer() {
         let mut buffer = Vec::new();
         let crc32 = 123456u32;
-        let footer: Footer = Footer::new(VersionedFooter::V2 {
+        let footer: Footer = Footer::new(VersionedFooter::V1 {
             crc32,
             store_compression: "lz4".to_string(),
         });
@@ -301,7 +276,7 @@ mod tests {
     #[test]
     fn footer_length() {
         let crc32 = 1111111u32;
-        let versioned_footer = VersionedFooter::V2 {
+        let versioned_footer = VersionedFooter::V1 {
             crc32,
             store_compression: "lz4".to_string(),
         };
@@ -322,7 +297,7 @@ mod tests {
             // versionned footer length
             12 | 128,
             // index format version
-            2,
+            1,
             0,
             0,
             0,
@@ -341,7 +316,7 @@ mod tests {
         let versioned_footer = VersionedFooter::deserialize(&mut cursor).unwrap();
         assert!(cursor.is_empty());
         let expected_crc: u32 = LittleEndian::read_u32(&v_footer_bytes[5..9]) as CrcHashU32;
-        let expected_versioned_footer: VersionedFooter = VersionedFooter::V2 {
+        let expected_versioned_footer: VersionedFooter = VersionedFooter::V1 {
             crc32: expected_crc,
             store_compression: "lz4".to_string(),
         };

src/directory/managed_directory.rs

@@ -1,5 +1,5 @@
-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;
@@ -11,9 +11,10 @@ use crate::error::DataCorruption;
 use crate::Directory;
 
 use crc32fast::Hasher;
-use slog::{debug, error, info};
+use serde_json;
 use std::collections::HashSet;
 use std::io;
+use std::io::Write;
 use std::path::{Path, PathBuf};
 use std::result;
 use std::sync::RwLockWriteGuard;
@@ -56,9 +57,9 @@ fn save_managed_paths(
     directory: &mut dyn Directory,
     wlock: &RwLockWriteGuard<'_, MetaInformation>,
 ) -> io::Result<()> {
-    let mut managed_json = serde_json::to_string_pretty(&wlock.managed_paths)?;
-    managed_json.push_str("\n");
-    directory.atomic_write(&MANAGED_FILEPATH, managed_json.as_bytes())?;
+    let mut w = serde_json::to_vec(&wlock.managed_paths)?;
+    writeln!(&mut w)?;
+    directory.atomic_write(&MANAGED_FILEPATH, &w[..])?;
     Ok(())
 }
 
@@ -86,12 +87,7 @@ impl ManagedDirectory {
                 directory: Box::new(directory),
                 meta_informations: Arc::default(),
             }),
-            Err(OpenReadError::IOError { io_error, filepath }) => {
-                Err(crate::TantivyError::OpenReadError(OpenReadError::IOError {
-                    io_error,
-                    filepath,
-                }))
-            }
+            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.
@@ -118,7 +114,7 @@ impl ManagedDirectory {
         &mut self,
         get_living_files: L,
     ) -> crate::Result<GarbageCollectionResult> {
-        info!(self.directory.logger(), "gc"; "stage"=>"start");
+        info!("Garbage collect");
         let mut files_to_delete = vec![];
 
         // It is crucial to get the living files after acquiring the
@@ -153,7 +149,7 @@ impl ManagedDirectory {
                     }
                 }
                 Err(err) => {
-                    error!(self.logger(), "Failed to acquire lock for GC");
+                    error!("Failed to acquire lock for GC");
                     return Err(crate::TantivyError::from(err));
                 }
             }
@@ -165,7 +161,7 @@ impl ManagedDirectory {
         for file_to_delete in files_to_delete {
             match self.delete(&file_to_delete) {
                 Ok(_) => {
-                    debug!(self.logger(), "deleted-success"; "file"=>format!("{:?}", file_to_delete));
+                    info!("Deleted {:?}", file_to_delete);
                     deleted_files.push(file_to_delete);
                 }
                 Err(file_error) => {
@@ -173,12 +169,12 @@ 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
                                 // is mmapped.
-                                error!(self.logger(), "delete-file-fail"; "path"=>file_to_delete.to_str().unwrap_or("<invalid-utf8>"));
+                                error!("Failed to delete {:?}", file_to_delete);
                             }
                         }
                     }
@@ -200,10 +196,6 @@ impl ManagedDirectory {
             save_managed_paths(self.directory.as_mut(), &meta_informations_wlock)?;
         }
 
-        info!(self.directory.logger(), "gc"; "stage"=>"end", 
-                "num-sucess-file-deletes"=>deleted_files.len(), 
-                "num-failed-file-deletes"=>failed_to_delete_files.len());
-
         Ok(GarbageCollectionResult {
             deleted_files,
             failed_to_delete_files,
@@ -240,11 +232,8 @@ 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 (footer, data) = Footer::extract_footer(reader)
+            .map_err(|err| IOError::with_path(path.to_path_buf(), err))?;
         let mut hasher = Hasher::new();
         hasher.update(data.as_slice());
         let crc = hasher.finalize();
@@ -257,46 +246,35 @@ impl ManagedDirectory {
 
     /// List files for which checksum does not match content
     pub fn list_damaged(&self) -> result::Result<HashSet<PathBuf>, OpenReadError> {
-        let mut managed_paths = self
+        let mut hashset = HashSet::new();
+        let managed_paths = self
             .meta_informations
             .read()
             .expect("Managed directory rlock poisoned in list damaged.")
             .managed_paths
             .clone();
 
-        managed_paths.remove(*META_FILEPATH);
-
-        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 open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
-        slog::debug!(self.logger(), "open-read"; "path" => path.to_str().unwrap_or("<invalid-utf8>"));
         let read_only_source = self.directory.open_read(path)?;
-        let (footer, reader) = Footer::extract_footer(read_only_source).map_err(|io_error| {
-            OpenReadError::IOError {
-                io_error,
-                filepath: path.to_path_buf(),
-            }
-        })?;
+        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(&mut self, path: &Path) -> result::Result<WritePtr, OpenWriteError> {
-        slog::debug!(self.logger(), "open-write"; "path" => path.to_str().unwrap_or("<invalid-utf8>"));
         self.register_file_as_managed(path)
-            .map_err(|io_error| OpenWriteError::IOError {
-                io_error,
-                filepath: 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)?
@@ -306,11 +284,9 @@ impl Directory for ManagedDirectory {
         ))))
     }
 
-    fn atomic_write(&mut self, path: &Path, content: &[u8]) -> io::Result<()> {
-        let content_str = std::str::from_utf8(content).unwrap_or("<content-not-utf-8>");
-        slog::debug!(self.logger(), "Atomic write"; "path" => format!("{:?}", path), "content_length"=>content_str);
+    fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
         self.register_file_as_managed(path)?;
-        self.directory.atomic_write(path, content)
+        self.directory.atomic_write(path, data)
     }
 
     fn atomic_read(&self, path: &Path) -> result::Result<Vec<u8>, OpenReadError> {
@@ -332,10 +308,6 @@ impl Directory for ManagedDirectory {
     fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle> {
         self.directory.watch(watch_callback)
     }
-
-    fn logger(&self) -> &slog::Logger {
-        self.directory.logger()
-    }
 }
 
 impl Clone for ManagedDirectory {

src/directory/mmap_directory.rs

@@ -1,6 +1,15 @@
+use fs2;
+use notify;
+
+use self::fs2::FileExt;
+use self::notify::RawEvent;
+use self::notify::RecursiveMode;
+use self::notify::Watcher;
 use crate::core::META_FILEPATH;
 use crate::directory::error::LockError;
-use crate::directory::error::{DeleteError, OpenDirectoryError, OpenReadError, OpenWriteError};
+use crate::directory::error::{
+    DeleteError, IOError, OpenDirectoryError, OpenReadError, OpenWriteError,
+};
 use crate::directory::read_only_source::BoxedData;
 use crate::directory::AntiCallToken;
 use crate::directory::Directory;
@@ -11,14 +20,9 @@ use crate::directory::WatchCallback;
 use crate::directory::WatchCallbackList;
 use crate::directory::WatchHandle;
 use crate::directory::{TerminatingWrite, WritePtr};
-use fs2::FileExt;
+use atomicwrites;
 use memmap::Mmap;
-use notify::RawEvent;
-use notify::RecursiveMode;
-use notify::Watcher;
 use serde::{Deserialize, Serialize};
-use slog::{debug, o, Drain, Logger};
-use slog_stdlog::StdLog;
 use std::collections::HashMap;
 use std::convert::From;
 use std::fmt;
@@ -36,6 +40,11 @@ use std::sync::Weak;
 use std::thread;
 use tempfile::TempDir;
 
+/// Create a default io error given a string.
+pub(crate) fn make_io_err(msg: String) -> io::Error {
+    io::Error::new(io::ErrorKind::Other, msg)
+}
+
 /// 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> {
@@ -43,17 +52,13 @@ fn open_mmap(full_path: &Path) -> result::Result<Option<Mmap>, OpenReadError> {
         if e.kind() == io::ErrorKind::NotFound {
             OpenReadError::FileDoesNotExist(full_path.to_owned())
         } else {
-            OpenReadError::IOError {
-                io_error: e,
-                filepath: full_path.to_owned(),
-            }
+            OpenReadError::IOError(IOError::with_path(full_path.to_owned(), e))
         }
     })?;
 
-    let meta_data = file.metadata().map_err(|e| OpenReadError::IOError {
-        io_error: e,
-        filepath: full_path.to_owned(),
-    })?;
+    let meta_data = file
+        .metadata()
+        .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
@@ -63,10 +68,7 @@ fn open_mmap(full_path: &Path) -> result::Result<Option<Mmap>, OpenReadError> {
     unsafe {
         memmap::Mmap::map(&file)
             .map(Some)
-            .map_err(|e| OpenReadError::IOError {
-                io_error: e,
-                filepath: full_path.to_owned(),
-            })
+            .map_err(|e| From::from(IOError::with_path(full_path.to_owned(), e)))
     }
 }
 
@@ -146,7 +148,7 @@ struct WatcherWrapper {
 }
 
 impl WatcherWrapper {
-    pub(crate) fn new(path: &Path, logger: Logger) -> Result<Self, OpenDirectoryError> {
+    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)
@@ -160,8 +162,7 @@ impl WatcherWrapper {
                     panic!("Unknown error while starting watching directory {:?}", path);
                 }
             })?;
-        let watcher_router: Arc<WatchCallbackList> =
-            Arc::new(WatchCallbackList::with_logger(logger));
+        let watcher_router: Arc<WatchCallbackList> = Default::default();
         let watcher_router_clone = watcher_router.clone();
         thread::Builder::new()
             .name("meta-file-watch-thread".to_string())
@@ -186,10 +187,6 @@ impl WatcherWrapper {
                         }
                     }
                 }
-            })
-            .map_err(|io_error| OpenDirectoryError::IoError {
-                io_error,
-                directory_path: path.to_path_buf(),
             })?;
         Ok(WatcherWrapper {
             _watcher: Mutex::new(watcher),
@@ -224,22 +221,20 @@ struct MmapDirectoryInner {
     mmap_cache: RwLock<MmapCache>,
     _temp_directory: Option<TempDir>,
     watcher: RwLock<Option<WatcherWrapper>>,
-    logger: Logger,
 }
 
 impl MmapDirectoryInner {
     fn new(
         root_path: PathBuf,
         temp_directory: Option<TempDir>,
-        logger: Logger,
-    ) -> MmapDirectoryInner {
-        MmapDirectoryInner {
+    ) -> Result<MmapDirectoryInner, OpenDirectoryError> {
+        let mmap_directory_inner = MmapDirectoryInner {
             root_path,
             mmap_cache: Default::default(),
             _temp_directory: temp_directory,
             watcher: RwLock::new(None),
-            logger,
-        }
+        };
+        Ok(mmap_directory_inner)
     }
 
     fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle> {
@@ -250,7 +245,7 @@ impl MmapDirectoryInner {
         // 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, self.logger.clone())?;
+            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.
@@ -273,11 +268,14 @@ impl fmt::Debug for MmapDirectory {
 }
 
 impl MmapDirectory {
-    fn new(root_path: PathBuf, temp_directory: Option<TempDir>, logger: Logger) -> MmapDirectory {
-        let inner = MmapDirectoryInner::new(root_path, temp_directory, logger);
-        MmapDirectory {
+    fn new(
+        root_path: PathBuf,
+        temp_directory: Option<TempDir>,
+    ) -> Result<MmapDirectory, OpenDirectoryError> {
+        let inner = MmapDirectoryInner::new(root_path, temp_directory)?;
+        Ok(MmapDirectory {
             inner: Arc::new(inner),
-        }
+        })
     }
 
     /// Creates a new MmapDirectory in a temporary directory.
@@ -285,19 +283,16 @@ impl MmapDirectory {
     /// This is mostly useful to test the MmapDirectory itself.
     /// For your unit tests, prefer the RAMDirectory.
     pub fn create_from_tempdir() -> Result<MmapDirectory, OpenDirectoryError> {
-        let tempdir = TempDir::new().map_err(OpenDirectoryError::FailedToCreateTempDir)?;
-        let logger = Logger::root(StdLog.fuse(), o!());
-        Ok(MmapDirectory::new(tempdir.path().to_owned(), Some(tempdir), logger))
+        let tempdir = TempDir::new().map_err(OpenDirectoryError::IoError)?;
+        let tempdir_path = PathBuf::from(tempdir.path());
+        MmapDirectory::new(tempdir_path, Some(tempdir))
     }
 
     /// Opens a MmapDirectory in a directory.
     ///
     /// Returns an error if the `directory_path` does not
     /// exist or if it is not a directory.
-    pub fn open_with_logger<P: AsRef<Path>>(
-        directory_path: P,
-        logger: Logger,
-    ) -> Result<MmapDirectory, OpenDirectoryError> {
+    pub fn open<P: AsRef<Path>>(directory_path: P) -> Result<MmapDirectory, OpenDirectoryError> {
         let directory_path: &Path = directory_path.as_ref();
         if !directory_path.exists() {
             Err(OpenDirectoryError::DoesNotExist(PathBuf::from(
@@ -308,20 +303,10 @@ impl MmapDirectory {
                 directory_path,
             )))
         } else {
-            Ok(MmapDirectory::new(
-                PathBuf::from(directory_path),
-                None,
-                logger,
-            ))
+            Ok(MmapDirectory::new(PathBuf::from(directory_path), None)?)
         }
     }
 
-    /// Creates an `MmapDirectory` at the given path.
-    pub fn open<P: AsRef<Path>>(directory_path: P) -> Result<MmapDirectory, OpenDirectoryError> {
-        let logger = Logger::root(StdLog.fuse(), o!());
-        Self::open_with_logger(directory_path, logger)
-    }
-
     /// Joins a relative_path to the directory `root_path`
     /// to create a proper complete `filepath`.
     fn resolve_path(&self, relative_path: &Path) -> PathBuf {
@@ -381,12 +366,11 @@ impl MmapDirectory {
 struct ReleaseLockFile {
     _file: File,
     path: PathBuf,
-    logger: Logger,
 }
 
 impl Drop for ReleaseLockFile {
     fn drop(&mut self) {
-        debug!(self.logger, "Releasing lock {:?}", self.path);
+        debug!("Releasing lock {:?}", self.path);
     }
 }
 
@@ -425,18 +409,16 @@ impl TerminatingWrite for SafeFileWriter {
 
 impl Directory for MmapDirectory {
     fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
+        debug!("Open Read {:?}", path);
         let full_path = self.resolve_path(path);
+
         let mut mmap_cache = self.inner.mmap_cache.write().map_err(|_| {
             let msg = format!(
                 "Failed to acquired write lock \
                  on mmap cache while reading {:?}",
                 path
             );
-            let io_error = io::Error::new(io::ErrorKind::Other, msg);
-            OpenReadError::IOError {
-                io_error,
-                filepath: path.to_owned(),
-            }
+            IOError::with_path(path.to_owned(), make_io_err(msg))
         })?;
         Ok(mmap_cache
             .get_mmap(&full_path)?
@@ -449,18 +431,14 @@ 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())
                 }
             }
         }
@@ -472,7 +450,9 @@ impl Directory for MmapDirectory {
     }
 
     fn open_write(&mut self, path: &Path) -> Result<WritePtr, OpenWriteError> {
+        debug!("Open Write {:?}", path);
         let full_path = self.resolve_path(path);
+
         let open_res = OpenOptions::new()
             .write(true)
             .create_new(true)
@@ -482,25 +462,18 @@ impl Directory for MmapDirectory {
             if err.kind() == io::ErrorKind::AlreadyExists {
                 OpenWriteError::FileAlreadyExists(path.to_owned())
             } else {
-                OpenWriteError::IOError {
-                    io_error: err,
-                    filepath: path.to_owned(),
-                }
+                IOError::with_path(path.to_owned(), err).into()
             }
         })?;
 
         // making sure the file is created.
-        file.flush().map_err(|io_error| OpenWriteError::IOError {
-            io_error,
-            filepath: path.to_owned(),
-        })?;
+        file.flush()
+            .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(|e| OpenWriteError::IOError {
-            io_error: e,
-            filepath: path.to_owned(),
-        })?;
+        self.sync_directory()
+            .map_err(|e| IOError::with_path(path.to_owned(), e))?;
 
         let writer = SafeFileWriter::new(file);
         Ok(BufWriter::new(Box::new(writer)))
@@ -512,31 +485,24 @@ impl Directory for MmapDirectory {
         match File::open(&full_path) {
             Ok(mut file) => {
                 file.read_to_end(&mut buffer)
-                    .map_err(|io_error| OpenReadError::IOError {
-                        io_error,
-                        filepath: path.to_owned(),
-                    })?;
+                    .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::IOError {
-                        io_error,
-                        filepath: path.to_owned(),
-                    })
+                    Err(IOError::with_path(path.to_owned(), e).into())
                 }
             }
         }
     }
 
-    fn atomic_write(&mut self, path: &Path, content: &[u8]) -> io::Result<()> {
-        let mut tempfile = tempfile::Builder::new().tempfile_in(&self.inner.root_path)?;
-        tempfile.write_all(content)?;
-        tempfile.flush()?;
+    fn atomic_write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
+        debug!("Atomic Write {:?}", path);
         let full_path = self.resolve_path(path);
-        tempfile.into_temp_path().persist(full_path)?;
+        let meta_file = atomicwrites::AtomicFile::new(full_path, atomicwrites::AllowOverwrite);
+        meta_file.write(|f| f.write_all(data))?;
         Ok(())
     }
 
@@ -553,22 +519,16 @@ impl Directory for MmapDirectory {
         } else {
             file.try_lock_exclusive().map_err(|_| LockError::LockBusy)?
         }
-        let logger = self.inner.logger.clone();
         // dropping the file handle will release the lock.
         Ok(DirectoryLock::from(Box::new(ReleaseLockFile {
             path: lock.filepath.clone(),
             _file: file,
-            logger,
         })))
     }
 
     fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle> {
         self.inner.watch(watch_callback)
     }
-
-    fn logger(&self) -> &Logger {
-        &self.inner.logger
-    }
 }
 
 #[cfg(test)]
@@ -678,8 +638,7 @@ mod tests {
         let counter_clone = counter.clone();
         let tmp_dir = tempfile::TempDir::new().unwrap();
         let tmp_dirpath = tmp_dir.path().to_owned();
-        let logger = Logger::root(slog::Discard, o!());
-        let mut watch_wrapper = WatcherWrapper::new(&tmp_dirpath, logger).unwrap();
+        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);
@@ -704,7 +663,7 @@ mod tests {
         {
             let index = Index::create(mmap_directory.clone(), schema).unwrap();
 
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             let mut log_merge_policy = LogMergePolicy::default();
             log_merge_policy.set_min_merge_size(3);
             index_writer.set_merge_policy(Box::new(log_merge_policy));

src/directory/mod.rs

@@ -13,7 +13,10 @@ mod footer;
 mod managed_directory;
 mod ram_directory;
 mod read_only_source;
+mod spilling_writer;
 mod watch_event_router;
+mod persistor;
+
 
 /// Errors specific to the directory module.
 pub mod error;
@@ -23,8 +26,8 @@ pub use self::directory::{Directory, DirectoryClone};
 pub use self::directory_lock::{Lock, INDEX_WRITER_LOCK, META_LOCK};
 pub use self::ram_directory::RAMDirectory;
 pub use self::read_only_source::ReadOnlySource;
-pub(crate) use self::watch_event_router::WatchCallbackList;
-pub use self::watch_event_router::{WatchCallback, WatchHandle};
+pub(crate) use self::spilling_writer::{SpillingResult, SpillingWriter};
+pub use self::watch_event_router::{WatchCallback, WatchCallbackList, WatchHandle};
 use std::io::{self, BufWriter, Write};
 use std::path::PathBuf;
 /// Outcome of the Garbage collection
@@ -80,10 +83,16 @@ impl<W: TerminatingWrite> TerminatingWrite for BufWriter<W> {
     }
 }
 
+impl TerminatingWrite for Vec<u8> {
+    fn terminate_ref(&mut self, _a: AntiCallToken) -> io::Result<()> {
+        Ok(())
+    }
+}
+
 #[cfg(test)]
 impl<'a> TerminatingWrite for &'a mut Vec<u8> {
     fn terminate_ref(&mut self, _a: AntiCallToken) -> io::Result<()> {
-        self.flush()
+        Ok(())
     }
 }
 

src/directory/persistor.rs

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

src/directory/ram_directory.rs

@@ -5,14 +5,13 @@ use crate::directory::WatchCallbackList;
 use crate::directory::{Directory, ReadOnlySource, WatchCallback, WatchHandle};
 use crate::directory::{TerminatingWrite, WritePtr};
 use fail::fail_point;
-use slog::{o, Drain, Logger};
-use slog_stdlog::StdLog;
 use std::collections::HashMap;
 use std::fmt;
 use std::io::{self, BufWriter, Cursor, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
 use std::result;
 use std::sync::{Arc, RwLock};
+use crate::indexer::ResourceManager;
 
 /// Writer associated with the `RAMDirectory`
 ///
@@ -68,7 +67,7 @@ impl Write for VecWriter {
 
     fn flush(&mut self) -> io::Result<()> {
         self.is_flushed = true;
-        let mut fs = self.shared_directory.fs.inner_directory.write().unwrap();
+        let mut fs = self.shared_directory.fs.write().unwrap();
         fs.write(self.path.clone(), self.data.get_ref());
         Ok(())
     }
@@ -80,21 +79,16 @@ impl TerminatingWrite for VecWriter {
     }
 }
 
+#[derive(Default)]
 struct InnerDirectory {
     fs: HashMap<PathBuf, ReadOnlySource>,
     watch_router: WatchCallbackList,
+    memory_manager: ResourceManager,
 }
 
 impl InnerDirectory {
-    fn with_logger(logger: Logger) -> Self {
-        InnerDirectory {
-            fs: Default::default(),
-            watch_router: WatchCallbackList::with_logger(logger.clone()),
-        }
-    }
-
     fn write(&mut self, path: PathBuf, data: &[u8]) -> bool {
-        let data = ReadOnlySource::new(Vec::from(data));
+        let data = ReadOnlySource::new_with_allocation(Vec::from(data), &self.memory_manager);
         self.fs.insert(path, data).is_some()
     }
 
@@ -120,15 +114,8 @@ impl InnerDirectory {
         self.watch_router.subscribe(watch_handle)
     }
 
-    fn total_mem_usage(&self) -> usize {
-        self.fs.values().map(|f| f.len()).sum()
-    }
-}
-
-impl Default for RAMDirectory {
-    fn default() -> RAMDirectory {
-        let logger = Logger::root(StdLog.fuse(), o!());
-        Self::with_logger(logger)
+    fn total_mem_usage(&self) -> u64 {
+        self.fs.values().map(|source| source.len() as u64).sum()
     }
 }
 
@@ -138,42 +125,42 @@ impl fmt::Debug for RAMDirectory {
     }
 }
 
-struct Inner {
-    inner_directory: RwLock<InnerDirectory>,
-    logger: Logger,
-}
-
 /// A Directory storing everything in anonymous memory.
 ///
 /// It is mainly meant for unit testing.
 /// Writes are only made visible upon flushing.
 ///
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct RAMDirectory {
-    fs: Arc<Inner>,
+    fs: Arc<RwLock<InnerDirectory>>,
 }
 
 impl RAMDirectory {
-    /// Constructor
+
+    /// Creates a new RAMDirectory.
+    ///
+    /// Check `.create_with_memory_manager(..)` if you want to associate an external memory
+    /// manager to your RAMDirectory.
     pub fn create() -> RAMDirectory {
-        Self::default()
+        RAMDirectory::default()
     }
 
-    /// Create a `RAMDirectory` with a custom logger.
-    pub fn with_logger(logger: Logger) -> RAMDirectory {
-        let inner_directory = InnerDirectory::with_logger(logger.clone()).into();
+    /// Constructor
+    pub fn create_with_memory_manager(memory_manager: ResourceManager) -> RAMDirectory {
+        let inner_directory = InnerDirectory {
+            fs: Default::default(),
+            watch_router: Default::default(),
+            memory_manager
+        };
         RAMDirectory {
-            fs: Arc::new(Inner {
-                inner_directory,
-                logger,
-            }),
+            fs: Arc::new(RwLock::new(inner_directory))
         }
     }
 
     /// Returns the sum of the size of the different files
     /// in the RAMDirectory.
-    pub fn total_mem_usage(&self) -> usize {
-        self.fs.inner_directory.read().unwrap().total_mem_usage()
+    pub fn total_mem_usage(&self) -> u64 {
+        self.fs.read().unwrap().total_mem_usage()
     }
 
     /// Write a copy of all of the files saved in the RAMDirectory in the target `Directory`.
@@ -183,7 +170,7 @@ impl RAMDirectory {
     ///
     /// If an error is encounterred, files may be persisted partially.
     pub fn persist(&self, dest: &mut dyn Directory) -> crate::Result<()> {
-        let wlock = self.fs.inner_directory.write().unwrap();
+        let wlock = self.fs.write().unwrap();
         for (path, source) in wlock.fs.iter() {
             let mut dest_wrt = dest.open_write(path)?;
             dest_wrt.write_all(source.as_slice())?;
@@ -195,25 +182,24 @@ impl RAMDirectory {
 
 impl Directory for RAMDirectory {
     fn open_read(&self, path: &Path) -> result::Result<ReadOnlySource, OpenReadError> {
-        self.fs.inner_directory.read().unwrap().open_read(path)
+        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.inner_directory.write().unwrap().delete(path)
+        self.fs.write().unwrap().delete(path)
     }
 
     fn exists(&self, path: &Path) -> bool {
-        self.fs.inner_directory.read().unwrap().exists(path)
+        self.fs.read().unwrap().exists(path)
     }
 
     fn open_write(&mut self, path: &Path) -> Result<WritePtr, OpenWriteError> {
-        let mut fs = self.fs.inner_directory.write().unwrap();
+        let mut fs = self.fs.write().unwrap();
         let path_buf = PathBuf::from(path);
         let vec_writer = VecWriter::new(path_buf.clone(), self.clone());
         let exists = fs.write(path_buf.clone(), &[]);
@@ -237,38 +223,19 @@ impl Directory for RAMDirectory {
         let path_buf = PathBuf::from(path);
 
         // Reserve the path to prevent calls to .write() to succeed.
-        self.fs
-            .inner_directory
-            .write()
-            .unwrap()
-            .write(path_buf.clone(), &[]);
+        self.fs.write().unwrap().write(path_buf.clone(), &[]);
 
         let mut vec_writer = VecWriter::new(path_buf, self.clone());
         vec_writer.write_all(data)?;
         vec_writer.flush()?;
         if path == Path::new(&*META_FILEPATH) {
-            let _ = self
-                .fs
-                .inner_directory
-                .write()
-                .unwrap()
-                .watch_router
-                .broadcast();
+            let _ = self.fs.write().unwrap().watch_router.broadcast();
         }
         Ok(())
     }
 
     fn watch(&self, watch_callback: WatchCallback) -> crate::Result<WatchHandle> {
-        Ok(self
-            .fs
-            .inner_directory
-            .write()
-            .unwrap()
-            .watch(watch_callback))
-    }
-
-    fn logger(&self) -> &Logger {
-        &self.fs.logger
+        Ok(self.fs.write().unwrap().watch(watch_callback))
     }
 }
 
@@ -278,6 +245,9 @@ mod tests {
     use crate::Directory;
     use std::io::Write;
     use std::path::Path;
+    use crate::indexer::ResourceManager;
+    use crate::directory::TerminatingWrite;
+    use std::mem;
 
     #[test]
     fn test_persist() {
@@ -295,4 +265,59 @@ mod tests {
         assert_eq!(directory_copy.atomic_read(path_atomic).unwrap(), msg_atomic);
         assert_eq!(directory_copy.atomic_read(path_seq).unwrap(), msg_seq);
     }
+
+    #[test]
+    fn test_memory_manager_several_path() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcd").is_ok());
+        assert_eq!(memory_manager.total_amount(), 4u64);
+        assert!(ram_directory.atomic_write(Path::new("/toto"), b"abcde").is_ok());
+        assert_eq!(memory_manager.total_amount(), 9u64);
+    }
+
+    #[test]
+    fn test_memory_manager_override() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcde").is_ok());
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcdef").is_ok());
+        assert_eq!(memory_manager.total_amount(), 6u64);
+    }
+
+    #[test]
+    fn test_memory_manager_seq_wrt() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        let mut wrt = ram_directory.open_write(Path::new("/titi")).unwrap();
+        assert!(wrt.write_all(b"abcde").is_ok());
+        assert!(wrt.terminate().is_ok());
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        assert!(ram_directory.atomic_write(Path::new("/titi"), b"abcdef").is_ok());
+        assert_eq!(memory_manager.total_amount(), 6u64);
+    }
+
+    #[test]
+    fn test_release_on_drop() {
+        let memory_manager = ResourceManager::default();
+        let mut ram_directory = RAMDirectory::create_with_memory_manager(memory_manager.clone());
+        let mut wrt = ram_directory.open_write(Path::new("/titi")).unwrap();
+        assert!(wrt.write_all(b"abcde").is_ok());
+        assert!(wrt.terminate().is_ok());
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        let mut wrt2 = ram_directory.open_write(Path::new("/toto")).unwrap();
+        assert!(wrt2.write_all(b"abcdefghijkl").is_ok());
+        assert!(wrt2.terminate().is_ok());
+        assert_eq!(memory_manager.total_amount(), 17u64);
+        let source = ram_directory.open_read(Path::new("/titi")).unwrap();
+        let source_clone = source.clone();
+        assert_eq!(memory_manager.total_amount(), 17u64);
+        mem::drop(ram_directory);
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        mem::drop(source);
+        assert_eq!(memory_manager.total_amount(), 5u64);
+        mem::drop(source_clone);
+        assert_eq!(memory_manager.total_amount(), 0u64);
+    }
 }

src/directory/read_only_source.rs

@@ -2,6 +2,7 @@ use crate::common::HasLen;
 use stable_deref_trait::{CloneStableDeref, StableDeref};
 use std::ops::Deref;
 use std::sync::Arc;
+use crate::indexer::{Allocation, ResourceManager};
 
 pub type BoxedData = Box<dyn Deref<Target = [u8]> + Send + Sync + 'static>;
 
@@ -15,6 +16,7 @@ pub struct ReadOnlySource {
     data: Arc<BoxedData>,
     start: usize,
     stop: usize,
+    allocation: Option<Arc<Allocation>>
 }
 
 unsafe impl StableDeref for ReadOnlySource {}
@@ -35,11 +37,13 @@ impl From<Arc<BoxedData>> for ReadOnlySource {
             data,
             start: 0,
             stop: len,
+            allocation: None
         }
     }
 }
 
 impl ReadOnlySource {
+
     pub(crate) fn new<D>(data: D) -> ReadOnlySource
     where
         D: Deref<Target = [u8]> + Send + Sync + 'static,
@@ -49,9 +53,24 @@ impl ReadOnlySource {
             data: Arc::new(Box::new(data)),
             start: 0,
             stop: len,
+            allocation: None
         }
     }
 
+    pub(crate) fn new_with_allocation<D>(data: D, memory_manager: &ResourceManager) -> ReadOnlySource
+        where
+            D: Deref<Target = [u8]> + Send + Sync + 'static,
+    {
+        let len = data.len();
+        ReadOnlySource {
+            data: Arc::new(Box::new(data)),
+            start: 0,
+            stop: len,
+            allocation: Some(Arc::new(memory_manager.allocate(len as u64)))
+        }
+    }
+
+
     /// Creates an empty ReadOnlySource
     pub fn empty() -> ReadOnlySource {
         ReadOnlySource::new(&[][..])
@@ -98,6 +117,7 @@ impl ReadOnlySource {
             data: self.data.clone(),
             start: self.start + start,
             stop: self.start + stop,
+            allocation: self.allocation.clone()
         }
     }
 

src/directory/spilling_writer.rs

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

src/directory/tests.rs

@@ -211,19 +211,19 @@ fn test_watch(directory: &mut dyn Directory) {
         .unwrap();
 
     for i in 0..10 {
-        assert!(i <= counter.load(SeqCst));
+        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!(i + 1 <= counter.load(SeqCst)); // notify can trigger more than once.
+        assert_eq!(i + 1, counter.load(SeqCst));
     }
     mem::drop(watch_handle);
     assert!(directory
         .atomic_write(Path::new("meta.json"), b"random_test_data")
         .is_ok());
     assert!(receiver.recv_timeout(Duration::from_millis(500)).is_ok());
-    assert!(10 <= counter.load(SeqCst));
+    assert_eq!(10, counter.load(SeqCst));
 }
 
 fn test_lock_non_blocking(directory: &mut dyn Directory) {

src/directory/watch_event_router.rs

@@ -1,20 +1,19 @@
 use futures::channel::oneshot;
 use futures::{Future, TryFutureExt};
-use slog::{error, Logger};
 use std::sync::Arc;
 use std::sync::RwLock;
 use std::sync::Weak;
 
 /// Type alias for callbacks registered when watching files of a `Directory`.
-pub type WatchCallback = Box<dyn Fn() + Sync + Send>;
+pub type WatchCallback = Box<dyn Fn() -> () + Sync + Send>;
 
 /// Helper struct to implement the watch method in `Directory` implementations.
 ///
 /// It registers callbacks (See `.subscribe(...)`) and
 /// calls them upon calls to `.broadcast(...)`.
-pub(crate) struct WatchCallbackList {
+#[derive(Default)]
+pub struct WatchCallbackList {
     router: RwLock<Vec<Weak<WatchCallback>>>,
-    logger: Logger,
 }
 
 /// Controls how long a directory should watch for a file change.
@@ -33,14 +32,7 @@ impl WatchHandle {
 }
 
 impl WatchCallbackList {
-    pub fn with_logger(logger: Logger) -> Self {
-        WatchCallbackList {
-            logger,
-            router: Default::default(),
-        }
-    }
-
-    /// Subscribes a new callback and returns a handle that controls the lifetime of the callback.
+    /// Suscribes a new callback and returns a handle that controls the lifetime of the callback.
     pub fn subscribe(&self, watch_callback: WatchCallback) -> WatchHandle {
         let watch_callback_arc = Arc::new(watch_callback);
         let watch_callback_weak = Arc::downgrade(&watch_callback_arc);
@@ -82,8 +74,8 @@ impl WatchCallbackList {
             });
         if let Err(err) = spawn_res {
             error!(
-                self.logger,
-                "Failed to spawn thread to call watch callbacks. Cause: {:?}", err
+                "Failed to spawn thread to call watch callbacks. Cause: {:?}",
+                err
             );
         }
         result
@@ -94,18 +86,13 @@ impl WatchCallbackList {
 mod tests {
     use crate::directory::WatchCallbackList;
     use futures::executor::block_on;
-    use slog::{o, Discard, Logger};
     use std::mem;
     use std::sync::atomic::{AtomicUsize, Ordering};
     use std::sync::Arc;
 
-    fn default_watch_callback_list() -> WatchCallbackList {
-        WatchCallbackList::with_logger(Logger::root(Discard, o!()))
-    }
-
     #[test]
     fn test_watch_event_router_simple() {
-        let watch_event_router = default_watch_callback_list();
+        let watch_event_router = WatchCallbackList::default();
         let counter: Arc<AtomicUsize> = Default::default();
         let counter_clone = counter.clone();
         let inc_callback = Box::new(move || {
@@ -132,7 +119,7 @@ mod tests {
 
     #[test]
     fn test_watch_event_router_multiple_callback_same_key() {
-        let watch_event_router = default_watch_callback_list();
+        let watch_event_router = WatchCallbackList::default();
         let counter: Arc<AtomicUsize> = Default::default();
         let inc_callback = |inc: usize| {
             let counter_clone = counter.clone();
@@ -161,7 +148,7 @@ mod tests {
 
     #[test]
     fn test_watch_event_router_multiple_callback_different_key() {
-        let watch_event_router = default_watch_callback_list();
+        let watch_event_router = WatchCallbackList::default();
         let counter: Arc<AtomicUsize> = Default::default();
         let counter_clone = counter.clone();
         let inc_callback = Box::new(move || {

src/docset.rs

@@ -1,48 +1,58 @@
+use crate::common::BitSet;
 use crate::fastfield::DeleteBitSet;
 use crate::DocId;
 use std::borrow::Borrow;
 use std::borrow::BorrowMut;
+use std::cmp::Ordering;
 
-/// Sentinel value returned when a DocSet has been entirely consumed.
-///
-/// This is not u32::MAX as one would have expected, due to the lack of SSE2 instructions
-/// to compare [u32; 4].
-pub const TERMINATED: DocId = std::i32::MAX as u32;
+/// Expresses the outcome of a call to `DocSet`'s `.skip_next(...)`.
+#[derive(PartialEq, Eq, Debug)]
+pub enum SkipResult {
+    /// target was in the docset
+    Reached,
+    /// target was not in the docset, skipping stopped as a greater element was found
+    OverStep,
+    /// the docset was entirely consumed without finding the target, nor any
+    /// element greater than the target.
+    End,
+}
 
 /// Represents an iterable set of sorted doc ids.
 pub trait DocSet {
     /// Goes to the next element.
-    ///
-    /// The DocId of the next element is returned.
-    /// In other words we should always have :
-    /// ```ignore
-    /// let doc = docset.advance();
-    /// assert_eq!(doc, docset.doc());
-    /// ```
-    ///
-    /// If we reached the end of the DocSet, TERMINATED should be returned.
-    ///
-    /// Calling `.advance()` on a terminated DocSet should be supported, and TERMINATED should
-    /// be returned.
-    /// TODO Test existing docsets.
-    fn advance(&mut self) -> DocId;
+    /// `.advance(...)` needs to be called a first time to point to the correct
+    /// element.
+    fn advance(&mut self) -> bool;
 
-    /// Advances the DocSet forward until reaching the target, or going to the
-    /// lowest DocId greater than the target.
+    /// After skipping, position the iterator in such a way that `.doc()`
+    /// will return a value greater than or equal to target.
     ///
-    /// If the end of the DocSet is reached, TERMINATED is returned.
+    /// SkipResult expresses whether the `target value` was reached, overstepped,
+    /// or if the `DocSet` was entirely consumed without finding any value
+    /// greater or equal to the `target`.
     ///
-    /// Calling `.seek(target)` on a terminated DocSet is legal. Implementation
-    /// of DocSet should support it.
+    /// WARNING: Calling skip always advances the docset.
+    /// More specifically, if the docset is already positionned on the target
+    /// skipping will advance to the next position and return SkipResult::Overstep.
     ///
-    /// Calling `seek(TERMINATED)` is also legal and is the normal way to consume a DocSet.
-    fn seek(&mut self, target: DocId) -> DocId {
-        let mut doc = self.doc();
-        debug_assert!(doc <= target);
-        while doc < target {
-            doc = self.advance();
+    /// If `.skip_next()` oversteps, then the docset must be positionned correctly
+    /// on an existing document. In other words, `.doc()` should return the first document
+    /// greater than `DocId`.
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
+        if !self.advance() {
+            return SkipResult::End;
+        }
+        loop {
+            match self.doc().cmp(&target) {
+                Ordering::Less => {
+                    if !self.advance() {
+                        return SkipResult::End;
+                    }
+                }
+                Ordering::Equal => return SkipResult::Reached,
+                Ordering::Greater => return SkipResult::OverStep,
+            }
         }
-        doc
     }
 
     /// Fills a given mutable buffer with the next doc ids from the
@@ -61,38 +71,38 @@ pub trait DocSet {
     /// use case where batching. The normal way to
     /// go through the `DocId`'s is to call `.advance()`.
     fn fill_buffer(&mut self, buffer: &mut [DocId]) -> usize {
-        if self.doc() == TERMINATED {
-            return 0;
-        }
         for (i, buffer_val) in buffer.iter_mut().enumerate() {
-            *buffer_val = self.doc();
-            if self.advance() == TERMINATED {
-                return i + 1;
+            if self.advance() {
+                *buffer_val = self.doc();
+            } else {
+                return i;
             }
         }
         buffer.len()
     }
 
     /// Returns the current document
-    /// Right after creating a new DocSet, the docset points to the first document.
-    ///
-    /// If the DocSet is empty, .doc() should return `TERMINATED`.
     fn doc(&self) -> DocId;
 
     /// Returns a best-effort hint of the
     /// length of the docset.
     fn size_hint(&self) -> u32;
 
+    /// Appends all docs to a `bitset`.
+    fn append_to_bitset(&mut self, bitset: &mut BitSet) {
+        while self.advance() {
+            bitset.insert(self.doc());
+        }
+    }
+
     /// Returns the number documents matching.
     /// Calling this method consumes the `DocSet`.
     fn count(&mut self, delete_bitset: &DeleteBitSet) -> u32 {
         let mut count = 0u32;
-        let mut doc = self.doc();
-        while doc != TERMINATED {
-            if !delete_bitset.is_deleted(doc) {
+        while self.advance() {
+            if !delete_bitset.is_deleted(self.doc()) {
                 count += 1u32;
             }
-            doc = self.advance();
         }
         count
     }
@@ -104,42 +114,22 @@ pub trait DocSet {
     /// given by `count()`.
     fn count_including_deleted(&mut self) -> u32 {
         let mut count = 0u32;
-        let mut doc = self.doc();
-        while doc != TERMINATED {
+        while self.advance() {
             count += 1u32;
-            doc = self.advance();
         }
         count
     }
 }
 
-impl<'a> DocSet for &'a mut dyn DocSet {
-    fn advance(&mut self) -> u32 {
-        (**self).advance()
-    }
-
-    fn seek(&mut self, target: DocId) -> DocId {
-        (**self).seek(target)
-    }
-
-    fn doc(&self) -> u32 {
-        (**self).doc()
-    }
-
-    fn size_hint(&self) -> u32 {
-        (**self).size_hint()
-    }
-}
-
 impl<TDocSet: DocSet + ?Sized> DocSet for Box<TDocSet> {
-    fn advance(&mut self) -> DocId {
+    fn advance(&mut self) -> bool {
         let unboxed: &mut TDocSet = self.borrow_mut();
         unboxed.advance()
     }
 
-    fn seek(&mut self, target: DocId) -> DocId {
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
         let unboxed: &mut TDocSet = self.borrow_mut();
-        unboxed.seek(target)
+        unboxed.skip_next(target)
     }
 
     fn doc(&self) -> DocId {
@@ -161,4 +151,9 @@ impl<TDocSet: DocSet + ?Sized> DocSet for Box<TDocSet> {
         let unboxed: &mut TDocSet = self.borrow_mut();
         unboxed.count_including_deleted()
     }
+
+    fn append_to_bitset(&mut self, bitset: &mut BitSet) {
+        let unboxed: &mut TDocSet = self.borrow_mut();
+        unboxed.append_to_bitset(bitset);
+    }
 }

src/error.rs

@@ -2,13 +2,12 @@
 
 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 serde_json;
 use std::fmt;
 use std::path::PathBuf;
 use std::sync::PoisonError;
@@ -45,47 +44,44 @@ 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),
 }
 
@@ -94,17 +90,31 @@ impl From<DataCorruption> for TantivyError {
         TantivyError::DataCorruption(data_corruption)
     }
 }
+
 impl From<FastFieldNotAvailableError> for TantivyError {
     fn from(fastfield_error: FastFieldNotAvailableError) -> TantivyError {
         TantivyError::SchemaError(format!("{}", fastfield_error))
     }
 }
+
 impl From<LockError> for TantivyError {
     fn from(lock_error: LockError) -> TantivyError {
         TantivyError::LockFailure(lock_error, None)
     }
 }
 
+impl From<IOError> for TantivyError {
+    fn from(io_error: IOError) -> TantivyError {
+        TantivyError::IOError(io_error)
+    }
+}
+
+impl From<io::Error> for TantivyError {
+    fn from(io_error: io::Error) -> TantivyError {
+        TantivyError::IOError(io_error.into())
+    }
+}
+
 impl From<query::QueryParserError> for TantivyError {
     fn from(parsing_error: query::QueryParserError) -> TantivyError {
         TantivyError::InvalidArgument(format!("Query is invalid. {:?}", parsing_error))
@@ -117,12 +127,49 @@ impl<Guard> From<PoisonError<Guard>> for TantivyError {
     }
 }
 
+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)
+            }
+        }
+    }
+}
+
 impl From<schema::DocParsingError> for TantivyError {
     fn from(error: schema::DocParsingError) -> TantivyError {
         TantivyError::InvalidArgument(format!("Failed to parse document {:?}", error))
     }
 }
 
+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 {
         let io_err = io::Error::from(error);

src/fastfield/bytes/mod.rs

@@ -15,7 +15,7 @@ mod tests {
         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().unwrap();
+        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]));

src/fastfield/delete.rs

@@ -9,8 +9,6 @@ use std::io::Write;
 /// Write a delete `BitSet`
 ///
 /// where `delete_bitset` is the set of deleted `DocId`.
-/// Warning: this function does not call terminate. The caller is in charge of
-/// closing the writer properly.
 pub fn write_delete_bitset(
     delete_bitset: &BitSet,
     max_doc: u32,
@@ -44,24 +42,6 @@ pub struct DeleteBitSet {
 }
 
 impl DeleteBitSet {
-    #[cfg(test)]
-    pub(crate) fn for_test(docs: &[DocId], max_doc: u32) -> DeleteBitSet {
-        use crate::directory::{Directory, RAMDirectory, TerminatingWrite};
-        use std::path::Path;
-        assert!(docs.iter().all(|&doc| doc < max_doc));
-        let mut bitset = BitSet::with_max_value(max_doc);
-        for &doc in docs {
-            bitset.insert(doc);
-        }
-        let 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 source = directory.open_read(path).unwrap();
-        Self::open(source)
-    }
-
     /// Opens a delete bitset given its data source.
     pub fn open(data: ReadOnlySource) -> DeleteBitSet {
         let num_deleted: usize = data
@@ -103,35 +83,42 @@ impl HasLen for DeleteBitSet {
 
 #[cfg(test)]
 mod tests {
-    use super::DeleteBitSet;
-    use crate::common::HasLen;
+    use super::*;
+    use crate::directory::*;
+    use std::path::PathBuf;
 
-    #[test]
-    fn test_delete_bitset_empty() {
-        let delete_bitset = DeleteBitSet::for_test(&[], 10);
-        for doc in 0..10 {
-            assert_eq!(delete_bitset.is_deleted(doc), !delete_bitset.is_alive(doc));
+    fn test_delete_bitset_helper(bitset: &BitSet, max_doc: u32) {
+        let test_path = PathBuf::from("test");
+        let mut directory = RAMDirectory::default();
+        {
+            let mut writer = directory.open_write(&*test_path).unwrap();
+            write_delete_bitset(bitset, max_doc, &mut writer).unwrap();
+            writer.terminate().unwrap();
         }
-        assert_eq!(delete_bitset.len(), 0);
+        let source = directory.open_read(&test_path).unwrap();
+        let delete_bitset = DeleteBitSet::open(source);
+        for doc in 0..max_doc {
+            assert_eq!(bitset.contains(doc), delete_bitset.is_deleted(doc as DocId));
+        }
+        assert_eq!(delete_bitset.len(), bitset.len());
     }
 
     #[test]
     fn test_delete_bitset() {
-        let delete_bitset = DeleteBitSet::for_test(&[1, 9], 10);
-        assert!(delete_bitset.is_alive(0));
-        assert!(delete_bitset.is_deleted(1));
-        assert!(delete_bitset.is_alive(2));
-        assert!(delete_bitset.is_alive(3));
-        assert!(delete_bitset.is_alive(4));
-        assert!(delete_bitset.is_alive(5));
-        assert!(delete_bitset.is_alive(6));
-        assert!(delete_bitset.is_alive(6));
-        assert!(delete_bitset.is_alive(7));
-        assert!(delete_bitset.is_alive(8));
-        assert!(delete_bitset.is_deleted(9));
-        for doc in 0..10 {
-            assert_eq!(delete_bitset.is_deleted(doc), !delete_bitset.is_alive(doc));
+        {
+            let mut bitset = BitSet::with_max_value(10);
+            bitset.insert(1);
+            bitset.insert(9);
+            test_delete_bitset_helper(&bitset, 10);
+        }
+        {
+            let mut bitset = BitSet::with_max_value(8);
+            bitset.insert(1);
+            bitset.insert(2);
+            bitset.insert(3);
+            bitset.insert(5);
+            bitset.insert(7);
+            test_delete_bitset_helper(&bitset, 8);
         }
-        assert_eq!(delete_bitset.len(), 2);
     }
 }

src/fastfield/error.rs

@@ -4,8 +4,8 @@ use std::result;
 /// `FastFieldNotAvailableError` is returned when the
 /// user requested for a fast field reader, and the field was not
 /// defined in the schema as a fast field.
-#[derive(Debug, Error)]
-#[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/mod.rs

@@ -474,7 +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();
@@ -511,7 +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()),

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),
@@ -186,7 +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));
@@ -221,7 +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/fieldnorm/mod.rs

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

src/fieldnorm/reader.rs

@@ -1,41 +1,6 @@
 use super::{fieldnorm_to_id, id_to_fieldnorm};
-use crate::common::CompositeFile;
 use crate::directory::ReadOnlySource;
-use crate::schema::Field;
-use crate::space_usage::PerFieldSpaceUsage;
 use crate::DocId;
-use std::sync::Arc;
-
-/// Reader for the fieldnorm (for each document, the number of tokens indexed in the
-/// field) of all indexed fields in the index.
-///
-/// Each fieldnorm is approximately compressed over one byte. We refer to this byte as
-/// `fieldnorm_id`.
-/// The mapping from `fieldnorm` to `fieldnorm_id` is given by monotonic.
-#[derive(Clone)]
-pub struct FieldNormReaders {
-    data: Arc<CompositeFile>,
-}
-
-impl FieldNormReaders {
-    /// Creates a field norm reader.
-    pub fn open(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) -> Option<FieldNormReader> {
-        self.data.open_read(field).map(FieldNormReader::open)
-    }
-
-    /// Return a break down of the space usage per field.
-    pub fn space_usage(&self) -> PerFieldSpaceUsage {
-        self.data.space_usage()
-    }
-}
 
 /// Reads the fieldnorm associated to a document.
 /// The fieldnorm represents the length associated to
@@ -54,7 +19,6 @@ impl FieldNormReaders {
 /// Apart from compression, this scale also makes it possible to
 /// precompute computationally expensive functions of the fieldnorm
 /// in a very short array.
-#[derive(Clone)]
 pub struct FieldNormReader {
     data: ReadOnlySource,
 }
@@ -65,11 +29,6 @@ impl FieldNormReader {
         FieldNormReader { data }
     }
 
-    /// Returns the number of documents in this segment.
-    pub fn num_docs(&self) -> u32 {
-        self.data.len() as u32
-    }
-
     /// Returns the `fieldnorm` associated to a doc id.
     /// The fieldnorm is a value approximating the number
     /// of tokens in a given field of the `doc_id`.
@@ -103,12 +62,13 @@ impl FieldNormReader {
     pub fn fieldnorm_to_id(fieldnorm: u32) -> u8 {
         fieldnorm_to_id(fieldnorm)
     }
+}
 
-    #[cfg(test)]
-    pub fn for_test(field_norms: &[u32]) -> FieldNormReader {
+#[cfg(test)]
+impl From<Vec<u32>> for FieldNormReader {
+    fn from(field_norms: Vec<u32>) -> FieldNormReader {
         let field_norms_id = field_norms
-            .iter()
-            .cloned()
+            .into_iter()
             .map(FieldNormReader::fieldnorm_to_id)
             .collect::<Vec<u8>>();
         let field_norms_data = ReadOnlySource::from(field_norms_id);
@@ -117,20 +77,3 @@ impl FieldNormReader {
         }
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use crate::fieldnorm::FieldNormReader;
-
-    #[test]
-    fn test_from_fieldnorms_array() {
-        let fieldnorms = &[1, 2, 3, 4, 1_000_000];
-        let fieldnorm_reader = FieldNormReader::for_test(fieldnorms);
-        assert_eq!(fieldnorm_reader.num_docs(), 5);
-        assert_eq!(fieldnorm_reader.fieldnorm(0), 1);
-        assert_eq!(fieldnorm_reader.fieldnorm(1), 2);
-        assert_eq!(fieldnorm_reader.fieldnorm(2), 3);
-        assert_eq!(fieldnorm_reader.fieldnorm(3), 4);
-        assert_eq!(fieldnorm_reader.fieldnorm(4), 983_064);
-    }
-}

src/fieldnorm/writer.rs

@@ -78,12 +78,11 @@ impl FieldNormsWriter {
     }
 
     /// Serialize the seen fieldnorm values to the serializer for all fields.
-    pub fn serialize(&self, mut fieldnorms_serializer: FieldNormsSerializer) -> io::Result<()> {
+    pub fn serialize(&self, fieldnorms_serializer: &mut FieldNormsSerializer) -> io::Result<()> {
         for &field in self.fields.iter() {
             let fieldnorm_values: &[u8] = &self.fieldnorms_buffer[field.field_id() as usize][..];
             fieldnorms_serializer.serialize_field(field, fieldnorm_values)?;
         }
-        fieldnorms_serializer.close()?;
         Ok(())
     }
 }

src/indexer/index_writer.rs

@@ -8,42 +8,37 @@ use crate::core::SegmentComponent;
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::core::SegmentReader;
-use crate::directory::TerminatingWrite;
 use crate::directory::{DirectoryLock, GarbageCollectionResult};
-use crate::docset::{DocSet, TERMINATED};
+use crate::directory::{TerminatingWrite, WatchCallbackList};
+use crate::docset::DocSet;
 use crate::error::TantivyError;
 use crate::fastfield::write_delete_bitset;
 use crate::indexer::delete_queue::{DeleteCursor, DeleteQueue};
 use crate::indexer::doc_opstamp_mapping::DocToOpstampMapping;
 use crate::indexer::operation::DeleteOperation;
+use crate::indexer::segment_manager::SegmentRegisters;
+use crate::indexer::segment_register::SegmentRegister;
 use crate::indexer::stamper::Stamper;
-use crate::indexer::MergePolicy;
-use crate::indexer::SegmentEntry;
+use crate::indexer::{SegmentEntry, ResourceManager};
 use crate::indexer::SegmentWriter;
+use crate::indexer::{IndexWriterConfig, MergePolicy};
+use crate::reader::NRTReader;
 use crate::schema::Document;
 use crate::schema::IndexRecordOption;
 use crate::schema::Term;
-use crate::Opstamp;
+use crate::tokenizer::TokenizerManager;
+use crate::{IndexReader, Opstamp};
 use crossbeam::channel;
 use futures::executor::block_on;
 use futures::future::Future;
-use slog::{error, info, Logger};
 use smallvec::smallvec;
 use smallvec::SmallVec;
 use std::mem;
 use std::ops::Range;
-use std::sync::Arc;
+use std::sync::{Arc, RwLock};
 use std::thread;
 use std::thread::JoinHandle;
 
-// Size of the margin for the heap. A segment is closed when the remaining memory
-// in the heap goes below MARGIN_IN_BYTES.
-pub const MARGIN_IN_BYTES: usize = 1_000_000;
-
-// We impose the memory per thread to be at least 3 MB.
-pub const HEAP_SIZE_MIN: usize = ((MARGIN_IN_BYTES as u32) * 3u32) as usize;
-pub const HEAP_SIZE_MAX: usize = u32::max_value() as usize - MARGIN_IN_BYTES;
-
 // Add document will block if the number of docs waiting in the queue to be indexed
 // reaches `PIPELINE_MAX_SIZE_IN_DOCS`
 const PIPELINE_MAX_SIZE_IN_DOCS: usize = 10_000;
@@ -70,8 +65,9 @@ pub struct IndexWriter {
     _directory_lock: Option<DirectoryLock>,
 
     index: Index,
+    config: IndexWriterConfig,
 
-    heap_size_in_bytes_per_thread: usize,
+    segment_registers: Arc<RwLock<SegmentRegisters>>,
 
     workers_join_handle: Vec<JoinHandle<crate::Result<()>>>,
 
@@ -81,13 +77,14 @@ pub struct IndexWriter {
     segment_updater: SegmentUpdater,
 
     worker_id: usize,
-
-    num_threads: usize,
-
     delete_queue: DeleteQueue,
 
     stamper: Stamper,
     committed_opstamp: Opstamp,
+
+    on_commit: WatchCallbackList,
+
+    memory_manager: ResourceManager,
 }
 
 fn compute_deleted_bitset(
@@ -113,15 +110,15 @@ fn compute_deleted_bitset(
         if let Some(mut docset) =
             inverted_index.read_postings(&delete_op.term, IndexRecordOption::Basic)
         {
-            let mut deleted_doc = docset.doc();
-            while deleted_doc != TERMINATED {
+            while docset.advance() {
+                let deleted_doc = docset.doc();
                 if deleted_doc < limit_doc {
                     delete_bitset.insert(deleted_doc);
                     might_have_changed = true;
                 }
-                deleted_doc = docset.advance();
             }
         }
+
         delete_cursor.advance();
     }
     Ok(might_have_changed)
@@ -134,7 +131,6 @@ fn compute_deleted_bitset(
 /// For instance, there was no delete operation between the state of the `segment_entry` and
 /// the `target_opstamp`, `segment_entry` is not updated.
 pub(crate) fn advance_deletes(
-    mut segment: Segment,
     segment_entry: &mut SegmentEntry,
     target_opstamp: Opstamp,
 ) -> crate::Result<()> {
@@ -143,25 +139,33 @@ pub(crate) fn advance_deletes(
         return Ok(());
     }
 
-    if segment_entry.delete_bitset().is_none() && segment_entry.delete_cursor().get().is_none() {
+    let delete_bitset_opt = segment_entry.take_delete_bitset();
+
+    // We avoid directly advancing the `SegmentEntry` delete cursor, because
+    // we do not want to end up in an invalid state if the delete bitset
+    // serialization fails.
+    let mut delete_cursor = segment_entry.delete_cursor();
+
+    if delete_bitset_opt.is_none() && segment_entry.delete_cursor().get().is_none() {
         // There has been no `DeleteOperation` between the segment status and `target_opstamp`.
         return Ok(());
     }
 
+    // We open our current serialized segment to compute the new deleted bitset.
+    let segment = segment_entry.segment().clone();
     let segment_reader = SegmentReader::open(&segment)?;
 
     let max_doc = segment_reader.max_doc();
-    let mut delete_bitset: BitSet = match segment_entry.delete_bitset() {
-        Some(previous_delete_bitset) => (*previous_delete_bitset).clone(),
-        None => BitSet::with_max_value(max_doc),
-    };
+
+    let mut delete_bitset: BitSet =
+        delete_bitset_opt.unwrap_or_else(|| BitSet::with_max_value(max_doc));
 
     let num_deleted_docs_before = segment.meta().num_deleted_docs();
 
     compute_deleted_bitset(
         &mut delete_bitset,
         &segment_reader,
-        segment_entry.delete_cursor(),
+        &mut delete_cursor,
         &DocToOpstampMapping::None,
         target_opstamp,
     )?;
@@ -180,37 +184,44 @@ pub(crate) fn advance_deletes(
     let num_deleted_docs: u32 = delete_bitset.len() as u32;
     if num_deleted_docs > num_deleted_docs_before {
         // There are new deletes. We need to write a new delete file.
-        segment = segment.with_delete_meta(num_deleted_docs as u32, target_opstamp);
-        let mut delete_file = segment.open_write(SegmentComponent::DELETE)?;
+        let mut delete_file = segment
+            .with_delete_meta(num_deleted_docs as u32, target_opstamp)
+            .open_write(SegmentComponent::DELETE)?;
         write_delete_bitset(&delete_bitset, max_doc, &mut delete_file)?;
         delete_file.terminate()?;
+        segment_entry.reset_delete_meta(num_deleted_docs as u32, target_opstamp);
     }
 
-    segment_entry.set_meta(segment.meta().clone());
+    // Regardless of whether we did end up having to write a new file or not
+    // we advance the `delete_cursor`. This is an optimisation. We want to ensure we do not
+    // check that a given deleted term does not match any of our docs more than once.
+    segment_entry.set_delete_cursor(delete_cursor);
     Ok(())
 }
 
 fn index_documents(
-    memory_budget: usize,
+    config: IndexWriterConfig,
     segment: Segment,
     grouped_document_iterator: &mut dyn Iterator<Item = OperationGroup>,
     segment_updater: &mut SegmentUpdater,
+    tokenizers: &TokenizerManager,
     mut delete_cursor: DeleteCursor,
-    logger: &Logger,
+    memory_manager: ResourceManager
 ) -> crate::Result<bool> {
     let schema = segment.schema();
 
-    info!(logger, "segment-index"; "stage"=>"start");
-    let mut segment_writer = SegmentWriter::for_segment(memory_budget, segment.clone(), &schema)?;
-    let mut buffer_limit_reached = false;
+    let mut segment_writer = SegmentWriter::for_segment(
+        &config, segment, &schema, tokenizers, memory_manager)?;
     for document_group in grouped_document_iterator {
         for doc in document_group {
             segment_writer.add_document(doc, &schema)?;
         }
         let mem_usage = segment_writer.mem_usage();
-        if mem_usage >= memory_budget - MARGIN_IN_BYTES {
-            buffer_limit_reached = true;
-
+        if mem_usage >= config.heap_size_before_flushing() {
+            info!(
+                "Buffer limit reached, flushing segment with maxdoc={}.",
+                segment_writer.max_doc()
+            );
             break;
         }
     }
@@ -225,44 +236,15 @@ fn index_documents(
     // the worker thread.
     assert!(max_doc > 0);
 
-    let doc_opstamps: Vec<Opstamp> = segment_writer.finalize()?;
-
-    let segment_with_max_doc = segment.with_max_doc(max_doc);
+    let (segment, doc_opstamps): (Segment, Vec<Opstamp>) = segment_writer.finalize()?;
 
     let last_docstamp: Opstamp = *(doc_opstamps.last().unwrap());
-    info!(
-        logger,
-        "segment-index";
-        "stage" => "serialize",
-        "cause" => if buffer_limit_reached { "buffer-limit" } else { "commit" },
-        "maxdoc" => max_doc,
-        "last_docstamp" => last_docstamp
-    );
 
-    let delete_bitset_opt = apply_deletes(
-        &segment_with_max_doc,
-        &mut delete_cursor,
-        &doc_opstamps,
-        last_docstamp,
-    )?;
+    let delete_bitset_opt =
+        apply_deletes(&segment, &mut delete_cursor, &doc_opstamps, last_docstamp)?;
 
-    let segment_entry = SegmentEntry::new(
-        segment_with_max_doc.meta().clone(),
-        delete_cursor,
-        delete_bitset_opt,
-    );
-
-    info!(
-        logger,
-        "segment-index";
-        "stage" => "publish",
-    );
+    let segment_entry = SegmentEntry::new(segment, delete_cursor, delete_bitset_opt);
     block_on(segment_updater.schedule_add_segment(segment_entry))?;
-    info!(
-        logger,
-        "segment-index";
-        "stage" => "end",
-    );
     Ok(true)
 }
 
@@ -313,21 +295,10 @@ impl IndexWriter {
     /// If the heap size per thread is too small, panics.
     pub(crate) fn new(
         index: &Index,
-        num_threads: usize,
-        heap_size_in_bytes_per_thread: usize,
+        mut config: IndexWriterConfig,
         directory_lock: DirectoryLock,
     ) -> crate::Result<IndexWriter> {
-        if heap_size_in_bytes_per_thread < HEAP_SIZE_MIN {
-            let err_msg = format!(
-                "The heap size per thread needs to be at least {}.",
-                HEAP_SIZE_MIN
-            );
-            return Err(TantivyError::InvalidArgument(err_msg));
-        }
-        if heap_size_in_bytes_per_thread >= HEAP_SIZE_MAX {
-            let err_msg = format!("The heap size per thread cannot exceed {}", HEAP_SIZE_MAX);
-            return Err(TantivyError::InvalidArgument(err_msg));
-        }
+        config.validate()?;
         let (document_sender, document_receiver): (OperationSender, OperationReceiver) =
             channel::bounded(PIPELINE_MAX_SIZE_IN_DOCS);
 
@@ -335,16 +306,26 @@ impl IndexWriter {
 
         let current_opstamp = index.load_metas()?.opstamp;
 
+        let meta = index.load_metas()?;
+
         let stamper = Stamper::new(current_opstamp);
 
+        let commited_segments = SegmentRegister::new(
+            index.directory(),
+            &index.schema(),
+            meta.segments,
+            &delete_queue.cursor(),
+        );
+        let segment_registers = Arc::new(RwLock::new(SegmentRegisters::new(commited_segments)));
+
         let segment_updater =
-            SegmentUpdater::create(index.clone(), stamper.clone(), &delete_queue.cursor())?;
+            SegmentUpdater::create(segment_registers.clone(), index.clone(), stamper.clone())?;
 
         let mut index_writer = IndexWriter {
             _directory_lock: Some(directory_lock),
 
-            heap_size_in_bytes_per_thread,
             index: index.clone(),
+            config,
 
             operation_receiver: document_receiver,
             operation_sender: document_sender,
@@ -352,7 +333,6 @@ impl IndexWriter {
             segment_updater,
 
             workers_join_handle: vec![],
-            num_threads,
 
             delete_queue,
 
@@ -360,25 +340,23 @@ impl IndexWriter {
             stamper,
 
             worker_id: 0,
+            segment_registers,
+            on_commit: Default::default(),
+
+            memory_manager: Default::default()
         };
         index_writer.start_workers()?;
         Ok(index_writer)
     }
 
-    pub(crate) fn logger(&self) -> &Logger {
-        self.index.logger()
-    }
-
     fn drop_sender(&mut self) {
         let (sender, _receiver) = channel::bounded(1);
-        self.operation_sender = sender;
+        mem::replace(&mut self.operation_sender, sender);
     }
 
     /// If there are some merging threads, blocks until they all finish their work and
     /// then drop the `IndexWriter`.
     pub fn wait_merging_threads(mut self) -> crate::Result<()> {
-        info!(self.logger(), "wait-merge-threads"; "stage"=>"start");
-
         // this will stop the indexing thread,
         // dropping the last reference to the segment_updater.
         self.drop_sender();
@@ -393,23 +371,11 @@ impl IndexWriter {
                 })?;
         }
 
-        let result = self
+        self
             .segment_updater
-            .wait_merging_thread()
-            .map_err(|_| TantivyError::ErrorInThread("Failed to join merging thread.".into()));
+            .wait_merging_thread();
 
-        if let Err(ref e) = result {
-            error!(self.logger(), "some merge thread failed"; "cause"=>e.to_string());
-        }
-        info!(self.logger(), "wait-merge-threads"; "stage"=>"stop");
-        result
-    }
-
-    #[doc(hidden)]
-    pub fn add_segment(&self, segment_meta: SegmentMeta) -> crate::Result<()> {
-        let delete_cursor = self.delete_queue.cursor();
-        let segment_entry = SegmentEntry::new(segment_meta, delete_cursor, None);
-        block_on(self.segment_updater.schedule_add_segment(segment_entry))
+        Ok(())
     }
 
     /// Creates a new segment.
@@ -432,8 +398,9 @@ impl IndexWriter {
 
         let mut delete_cursor = self.delete_queue.cursor();
 
-        let mem_budget = self.heap_size_in_bytes_per_thread;
         let index = self.index.clone();
+        let config = self.config.clone();
+        let memory_manager = self.memory_manager.clone();
         let join_handle: JoinHandle<crate::Result<()>> = thread::Builder::new()
             .name(format!("thrd-tantivy-index{}", self.worker_id))
             .spawn(move || {
@@ -461,16 +428,14 @@ impl IndexWriter {
                         return Ok(());
                     }
                     let segment = index.new_segment();
-                    let segment_id = segment.id();
                     index_documents(
-                        mem_budget,
+                        config.clone(),
                         segment,
                         &mut document_iterator,
                         &mut segment_updater,
+                        index.tokenizers(),
                         delete_cursor.clone(),
-                        &index
-                            .logger()
-                            .new(slog::o!("segment"=>segment_id.to_string())),
+                        memory_manager.clone()
                     )?;
                 }
             })?;
@@ -490,7 +455,7 @@ impl IndexWriter {
     }
 
     fn start_workers(&mut self) -> crate::Result<()> {
-        for _ in 0..self.num_threads {
+        for _ in 0..self.config.max_indexing_threads {
             self.add_indexing_worker()?;
         }
         Ok(())
@@ -567,7 +532,6 @@ impl IndexWriter {
     /// when no documents are remaining.
     ///
     /// Returns the former segment_ready channel.
-    #[allow(unused_must_use)]
     fn recreate_document_channel(&mut self) -> OperationReceiver {
         let (document_sender, document_receiver): (OperationSender, OperationReceiver) =
             channel::bounded(PIPELINE_MAX_SIZE_IN_DOCS);
@@ -584,10 +548,7 @@ impl IndexWriter {
     ///
     /// The opstamp at the last commit is returned.
     pub fn rollback(&mut self) -> crate::Result<Opstamp> {
-        info!(
-            self.logger(),
-            "Rolling back to opstamp {}", self.committed_opstamp
-        );
+        info!("Rolling back to opstamp {}", self.committed_opstamp);
         // marks the segment updater as killed. From now on, all
         // segment updates will be ignored.
         self.segment_updater.kill();
@@ -599,18 +560,14 @@ impl IndexWriter {
             .take()
             .expect("The IndexWriter does not have any lock. This is a bug, please report.");
 
-        let new_index_writer: IndexWriter = IndexWriter::new(
-            &self.index,
-            self.num_threads,
-            self.heap_size_in_bytes_per_thread,
-            directory_lock,
-        )?;
+        let new_index_writer: IndexWriter =
+            IndexWriter::new(&self.index, self.config.clone(), directory_lock)?;
 
         // the current `self` is dropped right away because of this call.
         //
         // This will drop the document queue, and the thread
         // should terminate.
-        *self = new_index_writer;
+        mem::replace(self, new_index_writer);
 
         // Drains the document receiver pipeline :
         // Workers don't need to index the pending documents.
@@ -643,9 +600,7 @@ impl IndexWriter {
     /// It is also possible to add a payload to the `commit`
     /// using this API.
     /// See [`PreparedCommit::set_payload()`](PreparedCommit.html)
-    pub fn prepare_commit(&mut self) -> crate::Result<PreparedCommit> {
-        let logger = self.logger().clone();
-
+    pub fn prepare_commit(&mut self, soft_commit: bool) -> crate::Result<PreparedCommit> {
         // Here, because we join all of the worker threads,
         // all of the segment update for this commit have been
         // sent.
@@ -656,10 +611,7 @@ impl IndexWriter {
         //
         // This will move uncommitted segments to the state of
         // committed segments.
-
-        let commit_opstamp = self.stamper.stamp();
-
-        info!(logger, "prepare-commit"; "opstamp" => commit_opstamp);
+        info!("Preparing commit");
 
         // this will drop the current document channel
         // and recreate a new one.
@@ -675,8 +627,9 @@ impl IndexWriter {
             self.add_indexing_worker()?;
         }
 
-        let prepared_commit = PreparedCommit::new(self, commit_opstamp);
-        info!(logger, "Prepared commit {}", commit_opstamp);
+        let commit_opstamp = self.stamper.stamp();
+        let prepared_commit = PreparedCommit::new(self, commit_opstamp, soft_commit);
+        info!("Prepared commit {}", commit_opstamp);
         Ok(prepared_commit)
     }
 
@@ -695,7 +648,25 @@ impl IndexWriter {
     /// that made it in the commit.
     ///
     pub fn commit(&mut self) -> crate::Result<Opstamp> {
-        self.prepare_commit()?.commit()
+        self.prepare_commit(false)?.commit()
+    }
+
+    pub fn soft_commit(&mut self) -> crate::Result<Opstamp> {
+        self.prepare_commit(true)?.commit()
+    }
+
+    pub(crate) fn trigger_commit(&self) -> impl Future<Output = ()> {
+        self.on_commit.broadcast()
+    }
+
+    pub fn reader(&self, num_searchers: usize) -> crate::Result<IndexReader> {
+        let nrt_reader = NRTReader::create(
+            num_searchers,
+            self.index.clone(),
+            self.segment_registers.clone(),
+            &self.on_commit,
+        )?;
+        Ok(IndexReader::NRT(nrt_reader))
     }
 
     pub(crate) fn segment_updater(&self) -> &SegmentUpdater {
@@ -838,7 +809,7 @@ mod tests {
         let mut schema_builder = schema::Schema::builder();
         let text_field = schema_builder.add_text_field("text", schema::TEXT);
         let index = Index::create_in_ram(schema_builder.build());
-        let index_writer = index.writer_for_tests().unwrap();
+        let index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let operations = vec![
             UserOperation::Add(doc!(text_field=>"a")),
             UserOperation::Add(doc!(text_field=>"b")),
@@ -853,7 +824,7 @@ mod tests {
         let text_field = schema_builder.add_text_field("text", schema::TEXT);
         let index = Index::create_in_ram(schema_builder.build());
 
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(text_field => "hello1"));
         index_writer.add_document(doc!(text_field => "hello2"));
         assert!(index_writer.commit().is_ok());
@@ -902,7 +873,7 @@ mod tests {
             .reload_policy(ReloadPolicy::Manual)
             .try_into()
             .unwrap();
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         let a_term = Term::from_field_text(text_field, "a");
         let b_term = Term::from_field_text(text_field, "b");
         let operations = vec![
@@ -964,8 +935,8 @@ mod tests {
     fn test_lockfile_already_exists_error_msg() {
         let schema_builder = schema::Schema::builder();
         let index = Index::create_in_ram(schema_builder.build());
-        let _index_writer = index.writer_for_tests().unwrap();
-        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`"));
@@ -1093,7 +1064,8 @@ mod tests {
                 index_writer.add_document(doc!(text_field => "a"));
             }
             {
-                let mut prepared_commit = index_writer.prepare_commit().expect("commit failed");
+                let mut prepared_commit =
+                    index_writer.prepare_commit(false).expect("commit failed");
                 prepared_commit.set_payload("first commit");
                 prepared_commit.commit().expect("commit failed");
             }
@@ -1126,7 +1098,8 @@ mod tests {
                 index_writer.add_document(doc!(text_field => "a"));
             }
             {
-                let mut prepared_commit = index_writer.prepare_commit().expect("commit failed");
+                let mut prepared_commit =
+                    index_writer.prepare_commit(false).expect("commit failed");
                 prepared_commit.set_payload("first commit");
                 prepared_commit.abort().expect("commit failed");
             }
@@ -1299,9 +1272,46 @@ mod tests {
         let idfield = schema_builder.add_text_field("id", STRING);
         schema_builder.add_text_field("optfield", STRING);
         let index = Index::create_in_ram(schema_builder.build());
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.add_document(doc!(idfield=>"myid"));
         let commit = index_writer.commit();
         assert!(commit.is_ok());
     }
+
+    #[test]
+    fn test_index_writer_reader() {
+        let mut schema_builder = schema::Schema::builder();
+        let idfield = schema_builder.add_text_field("id", STRING);
+        schema_builder.add_text_field("optfield", STRING);
+        let index = Index::create_in_ram(schema_builder.build());
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(idfield=>"myid"));
+        assert!(index_writer.commit().is_ok());
+        let reader = index_writer.reader(2).unwrap();
+        let searcher = reader.searcher();
+        assert_eq!(searcher.num_docs(), 1u64);
+        index_writer.add_document(doc!(idfield=>"myid"));
+        assert!(index_writer.commit().is_ok());
+        assert_eq!(reader.searcher().num_docs(), 2u64);
+        assert_eq!(searcher.num_docs(), 1u64);
+    }
+
+    #[test]
+    fn test_index_writer_reader_soft_commit() {
+        let mut schema_builder = schema::Schema::builder();
+        let idfield = schema_builder.add_text_field("id", STRING);
+        schema_builder.add_text_field("optfield", STRING);
+        let index = Index::create_in_ram(schema_builder.build());
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(idfield=>"myid"));
+        assert!(index_writer.soft_commit().is_ok());
+        let nrt_reader = index_writer.reader(2).unwrap();
+        let normal_reader = index.reader_builder().try_into().unwrap();
+        assert_eq!(nrt_reader.searcher().num_docs(), 1u64);
+        assert_eq!(normal_reader.searcher().num_docs(), 0u64);
+        assert!(index_writer.commit().is_ok());
+        assert!(normal_reader.reload().is_ok());
+        assert_eq!(nrt_reader.searcher().num_docs(), 1u64);
+        assert_eq!(normal_reader.searcher().num_docs(), 1u64);
+    }
 }

src/indexer/index_writer_config.rs

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

src/indexer/log_merge_policy.rs

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

src/indexer/merge_operation.rs

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

src/indexer/merger.rs

@@ -2,37 +2,38 @@ use crate::common::MAX_DOC_LIMIT;
 use crate::core::Segment;
 use crate::core::SegmentReader;
 use crate::core::SerializableSegment;
-use crate::docset::{DocSet, TERMINATED};
+use crate::directory::TerminatingWrite;
+use crate::directory::WritePtr;
+use crate::docset::DocSet;
 use crate::fastfield::BytesFastFieldReader;
 use crate::fastfield::DeleteBitSet;
 use crate::fastfield::FastFieldReader;
 use crate::fastfield::FastFieldSerializer;
 use crate::fastfield::MultiValueIntFastFieldReader;
+use crate::fieldnorm::FieldNormReader;
 use crate::fieldnorm::FieldNormsSerializer;
 use crate::fieldnorm::FieldNormsWriter;
-use crate::fieldnorm::{FieldNormReader, FieldNormReaders};
 use crate::indexer::SegmentSerializer;
+use crate::postings::InvertedIndexSerializer;
 use crate::postings::Postings;
-use crate::postings::{InvertedIndexSerializer, SegmentPostings};
 use crate::schema::Cardinality;
 use crate::schema::FieldType;
 use crate::schema::{Field, Schema};
 use crate::store::StoreWriter;
 use crate::termdict::TermMerger;
 use crate::termdict::TermOrdinal;
-use crate::{DocId, InvertedIndexReader, SegmentComponent};
+use crate::DocId;
 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;
@@ -41,7 +42,7 @@ fn compute_total_num_tokens(readers: &[SegmentReader], field: Field) -> crate::R
             total_tokens += reader.inverted_index(field).total_num_tokens();
         }
     }
-    Ok(total_tokens
+    total_tokens
         + count
             .iter()
             .cloned()
@@ -49,7 +50,7 @@ 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 {
@@ -168,14 +169,14 @@ impl IndexMerger {
 
     fn write_fieldnorms(
         &self,
-        mut fieldnorms_serializer: FieldNormsSerializer,
+        fieldnorms_serializer: &mut FieldNormsSerializer,
     ) -> crate::Result<()> {
         let fields = FieldNormsWriter::fields_with_fieldnorm(&self.schema);
         let mut fieldnorms_data = Vec::with_capacity(self.max_doc as usize);
         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);
@@ -183,7 +184,6 @@ impl IndexMerger {
             }
             fieldnorms_serializer.serialize_field(field, &fieldnorms_data[..])?;
         }
-        fieldnorms_serializer.close()?;
         Ok(())
     }
 
@@ -494,11 +494,10 @@ impl IndexMerger {
         indexed_field: Field,
         field_type: &FieldType,
         serializer: &mut InvertedIndexSerializer,
-        fieldnorm_reader: Option<FieldNormReader>,
     ) -> crate::Result<Option<TermOrdinalMapping>> {
         let mut positions_buffer: Vec<u32> = Vec::with_capacity(1_000);
         let mut delta_computer = DeltaComputer::new();
-        let field_readers: Vec<Arc<InvertedIndexReader>> = self
+        let field_readers = self
             .readers
             .iter()
             .map(|reader| reader.inverted_index(indexed_field))
@@ -541,7 +540,7 @@ 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.
@@ -553,8 +552,7 @@ impl IndexMerger {
         // - Segment 2's doc ids become  [seg0.max_doc + seg1.max_doc,
         //                                seg0.max_doc + seg1.max_doc + seg2.max_doc]
         // ...
-        let mut field_serializer =
-            serializer.new_field(indexed_field, total_num_tokens, fieldnorm_reader)?;
+        let mut field_serializer = serializer.new_field(indexed_field, total_num_tokens)?;
 
         let field_entry = self.schema.get_field_entry(indexed_field);
 
@@ -564,78 +562,84 @@ impl IndexMerger {
                          indexed. Have you modified the schema?",
         );
 
-        let mut segment_postings_containing_the_term: Vec<(usize, SegmentPostings)> = vec![];
-
         while merged_terms.advance() {
-            segment_postings_containing_the_term.clear();
             let term_bytes: &[u8] = merged_terms.key();
 
-            let mut total_doc_freq = 0;
-
             // Let's compute the list of non-empty posting lists
-            for heap_item in merged_terms.current_kvs() {
-                let segment_ord = heap_item.segment_ord;
-                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 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)
-                } else {
-                    segment_postings.doc_freq()
-                };
-                if doc_freq > 0u32 {
-                    total_doc_freq += doc_freq;
-                    segment_postings_containing_the_term.push((segment_ord, segment_postings));
-                }
-            }
+            let segment_postings: Vec<_> = merged_terms
+                .current_kvs()
+                .iter()
+                .flat_map(|heap_item| {
+                    let segment_ord = heap_item.segment_ord;
+                    let term_info = heap_item.streamer.value();
+                    let segment_reader = &self.readers[heap_item.segment_ord];
+                    let inverted_index = segment_reader.inverted_index(indexed_field);
+                    let mut segment_postings = inverted_index
+                        .read_postings_from_terminfo(term_info, segment_postings_option);
+                    while segment_postings.advance() {
+                        if !segment_reader.is_deleted(segment_postings.doc()) {
+                            return Some((segment_ord, segment_postings));
+                        }
+                    }
+                    None
+                })
+                .collect();
 
             // At this point, `segment_postings` contains the posting list
-            // of all of the segments containing the given term (and that are non-empty)
+            // of all of the segments containing the given term.
             //
             // These segments are non-empty and advance has already been called.
-            if total_doc_freq == 0u32 {
-                // All docs that used to contain the term have been deleted. The `term` will be
-                // entirely removed.
-                continue;
-            }
+            if !segment_postings.is_empty() {
+                // If not, the `term` will be entirely removed.
 
-            let to_term_ord = field_serializer.new_term(term_bytes, total_doc_freq)?;
+                // We know that there is at least one document containing
+                // the term, so we add it.
+                let to_term_ord = field_serializer.new_term(term_bytes)?;
 
-            if let Some(ref mut term_ord_mapping) = term_ord_mapping_opt {
-                for (segment_ord, from_term_ord) in merged_terms.matching_segments() {
-                    term_ord_mapping.register_from_to(segment_ord, from_term_ord, to_term_ord);
-                }
-            }
-
-            // We can now serialize this postings, by pushing each document to the
-            // postings serializer.
-            for (segment_ord, mut segment_postings) in
-                segment_postings_containing_the_term.drain(..)
-            {
-                let old_to_new_doc_id = &merged_doc_id_map[segment_ord];
-
-                let mut doc = segment_postings.doc();
-                while doc != TERMINATED {
-                    // deleted doc are skipped as they do not have a `remapped_doc_id`.
-                    if let Some(remapped_doc_id) = old_to_new_doc_id[doc as usize] {
-                        // we make sure to only write the term iff
-                        // there is at least one document.
-                        let term_freq = segment_postings.term_freq();
-                        segment_postings.positions(&mut positions_buffer);
-
-                        let delta_positions = delta_computer.compute_delta(&positions_buffer);
-                        field_serializer.write_doc(remapped_doc_id, term_freq, delta_positions)?;
+                if let Some(ref mut term_ord_mapping) = term_ord_mapping_opt {
+                    for (segment_ord, from_term_ord) in merged_terms.matching_segments() {
+                        term_ord_mapping.register_from_to(segment_ord, from_term_ord, to_term_ord);
                     }
-
-                    doc = segment_postings.advance();
                 }
-            }
 
-            // closing the term.
-            field_serializer.close_term()?;
+                // We can now serialize this postings, by pushing each document to the
+                // postings serializer.
+                for (segment_ord, mut segment_postings) in segment_postings {
+                    let old_to_new_doc_id = &merged_doc_id_map[segment_ord];
+                    loop {
+                        let doc = segment_postings.doc();
+
+                        // `.advance()` has been called once before the loop.
+                        //
+                        // It was required to make sure we only consider segments
+                        // that effectively contain at least one non-deleted document
+                        // and remove terms that do not have documents associated.
+                        //
+                        //  For this reason, we cannot use a `while segment_postings.advance()` loop.
+
+                        // deleted doc are skipped as they do not have a `remapped_doc_id`.
+                        if let Some(remapped_doc_id) = old_to_new_doc_id[doc as usize] {
+                            // we make sure to only write the term iff
+                            // there is at least one document.
+                            let term_freq = segment_postings.term_freq();
+                            segment_postings.positions(&mut positions_buffer);
+
+                            let delta_positions = delta_computer.compute_delta(&positions_buffer);
+                            field_serializer.write_doc(
+                                remapped_doc_id,
+                                term_freq,
+                                delta_positions,
+                            )?;
+                        }
+                        if !segment_postings.advance() {
+                            break;
+                        }
+                    }
+                }
+
+                // closing the term.
+                field_serializer.close_term()?;
+            }
         }
         field_serializer.close()?;
         Ok(term_ord_mapping_opt)
@@ -644,18 +648,13 @@ impl IndexMerger {
     fn write_postings(
         &self,
         serializer: &mut InvertedIndexSerializer,
-        fieldnorm_readers: FieldNormReaders,
     ) -> 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);
             if field_entry.is_indexed() {
-                if let Some(term_ordinal_mapping) = self.write_postings_for_field(
-                    field,
-                    field_entry.field_type(),
-                    serializer,
-                    fieldnorm_reader,
-                )? {
+                if let Some(term_ordinal_mapping) =
+                    self.write_postings_for_field(field, field_entry.field_type(), serializer)?
+                {
                     term_ordinal_mappings.insert(field, term_ordinal_mapping);
                 }
             }
@@ -663,7 +662,8 @@ impl IndexMerger {
         Ok(term_ordinal_mappings)
     }
 
-    fn write_storable_fields(&self, store_writer: &mut StoreWriter) -> crate::Result<()> {
+    pub fn write_storable_fields(&self, store_wrt: WritePtr) -> crate::Result<()> {
+        let mut store_writer = StoreWriter::new(store_wrt);
         for reader in &self.readers {
             let store_reader = reader.get_store_reader();
             if reader.num_deleted_docs() > 0 {
@@ -675,23 +675,17 @@ impl IndexMerger {
                 store_writer.stack(&store_reader)?;
             }
         }
+        let store_wrt = store_writer.close()?;
+        store_wrt.terminate()?;
         Ok(())
     }
 }
 
 impl SerializableSegment for IndexMerger {
     fn write(&self, mut serializer: SegmentSerializer) -> crate::Result<u32> {
-        if let Some(fieldnorms_serializer) = serializer.extract_fieldnorms_serializer() {
-            self.write_fieldnorms(fieldnorms_serializer)?;
-        }
-        let fieldnorm_data = serializer
-            .segment()
-            .open_read(SegmentComponent::FIELDNORMS)?;
-        let fieldnorm_readers = FieldNormReaders::open(fieldnorm_data)?;
-        let term_ord_mappings =
-            self.write_postings(serializer.get_postings_serializer(), fieldnorm_readers)?;
+        let term_ord_mappings = self.write_postings(serializer.get_postings_serializer())?;
+        self.write_fieldnorms(serializer.get_fieldnorms_serializer())?;
         self.write_fast_fields(serializer.get_fast_field_serializer(), term_ord_mappings)?;
-        self.write_storable_fields(serializer.get_store_writer())?;
         serializer.close()?;
         Ok(self.max_doc)
     }
@@ -699,15 +693,15 @@ impl SerializableSegment for IndexMerger {
 
 #[cfg(test)]
 mod tests {
-    use crate::assert_nearly_equals;
     use crate::collector::tests::TEST_COLLECTOR_WITH_SCORE;
     use crate::collector::tests::{BytesFastFieldTestCollector, FastFieldTestCollector};
     use crate::collector::{Count, FacetCollector};
     use crate::core::Index;
     use crate::query::AllQuery;
     use crate::query::BooleanQuery;
-    use crate::query::Scorer;
     use crate::query::TermQuery;
+    use crate::schema;
+    use crate::schema::Cardinality;
     use crate::schema::Document;
     use crate::schema::Facet;
     use crate::schema::IndexRecordOption;
@@ -715,11 +709,9 @@ mod tests {
     use crate::schema::Term;
     use crate::schema::TextFieldIndexing;
     use crate::schema::INDEXED;
-    use crate::schema::{Cardinality, TEXT};
     use crate::DocAddress;
     use crate::IndexWriter;
     use crate::Searcher;
-    use crate::{schema, DocSet, SegmentId};
     use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
     use futures::executor::block_on;
     use std::io::Cursor;
@@ -751,7 +743,7 @@ mod tests {
         };
 
         {
-            let mut index_writer = index.writer_for_tests().unwrap();
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             {
                 // writing the segment
                 {
@@ -803,7 +795,7 @@ 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();
         }
@@ -904,7 +896,7 @@ mod tests {
         let score_field = schema_builder.add_u64_field("score", score_fieldtype);
         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().unwrap();
+        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);
@@ -1211,7 +1203,7 @@ 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 {
@@ -1276,7 +1268,7 @@ 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();
@@ -1295,7 +1287,7 @@ 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);
@@ -1320,7 +1312,7 @@ 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));
@@ -1349,7 +1341,7 @@ 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());
@@ -1388,7 +1380,7 @@ 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 {
@@ -1462,7 +1454,7 @@ 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());
         }
@@ -1516,7 +1508,7 @@ 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();
@@ -1526,9 +1518,12 @@ mod tests {
         for i in 0..100 {
             let mut doc = Document::new();
             doc.add_f64(field, 42.0);
+
             doc.add_f64(multi_field, 0.24);
             doc.add_f64(multi_field, 0.27);
+
             writer.add_document(doc);
+
             if i % 5 == 0 {
                 writer.commit()?;
             }
@@ -1540,72 +1535,6 @@ mod tests {
         // If a merging thread fails, we should end up with more
         // than one segment here
         assert_eq!(1, index.searchable_segments()?.len());
-        Ok(())
-    }
-
-    #[test]
-    fn test_merged_index_has_blockwand() -> crate::Result<()> {
-        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 happy_term = Term::from_field_text(text, "happy");
-        let term_query = TermQuery::new(happy_term, IndexRecordOption::WithFreqs);
-        for _ in 0..62 {
-            writer.add_document(doc!(text=>"hello happy tax payer"));
-        }
-        writer.commit()?;
-        let reader = index.reader()?;
-        let searcher = reader.searcher();
-        let mut term_scorer = term_query
-            .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);
-        assert_nearly_equals!(term_scorer.score(), 0.0079681855);
-        for _ in 0..81 {
-            writer.add_document(doc!(text=>"hello happy tax payer"));
-        }
-        writer.commit()?;
-        reader.reload()?;
-        let searcher = reader.searcher();
-
-        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_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() {
-                assert_eq!(term_scorer.doc(), doc);
-                assert_nearly_equals!(term_scorer.block_max_score(), 0.003478312);
-                assert_nearly_equals!(term_scorer.score(), 0.003478312);
-                term_scorer.advance();
-            }
-        }
-
-        let segment_ids: Vec<SegmentId> = searcher
-            .segment_readers()
-            .iter()
-            .map(|reader| reader.segment_id())
-            .collect();
-        block_on(writer.merge(&segment_ids[..]))?;
-
-        reader.reload()?;
-        let searcher = reader.searcher();
-        assert_eq!(searcher.segment_readers().len(), 1);
-
-        let segment_reader = searcher.segment_reader(0u32);
-        let mut term_scorer = term_query
-            .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() {
-            assert_eq!(term_scorer.doc(), doc);
-            assert_nearly_equals!(term_scorer.block_max_score(), 0.003478312);
-            assert_nearly_equals!(term_scorer.score(), 0.003478312);
-            term_scorer.advance();
-        }
 
         Ok(())
     }

src/indexer/mod.rs

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

src/indexer/prepared_commit.rs

@@ -1,21 +1,26 @@
 use super::IndexWriter;
 use crate::Opstamp;
 use futures::executor::block_on;
-use slog::info;
 
 /// A prepared commit
 pub struct PreparedCommit<'a> {
     index_writer: &'a mut IndexWriter,
     payload: Option<String>,
     opstamp: Opstamp,
+    soft_commit: bool,
 }
 
 impl<'a> PreparedCommit<'a> {
-    pub(crate) fn new(index_writer: &'a mut IndexWriter, opstamp: Opstamp) -> PreparedCommit<'_> {
+    pub(crate) fn new(
+        index_writer: &'a mut IndexWriter,
+        opstamp: Opstamp,
+        soft_commit: bool,
+    ) -> PreparedCommit<'_> {
         PreparedCommit {
             index_writer,
             payload: None,
             opstamp,
+            soft_commit,
         }
     }
 
@@ -32,12 +37,13 @@ impl<'a> PreparedCommit<'a> {
     }
 
     pub fn commit(self) -> crate::Result<Opstamp> {
-        info!(self.index_writer.logger(), "committing {}", self.opstamp);
-        let _ = block_on(
-            self.index_writer
-                .segment_updater()
-                .schedule_commit(self.opstamp, self.payload),
-        );
+        info!("committing {}", self.opstamp);
+        block_on(self.index_writer.segment_updater().schedule_commit(
+            self.opstamp,
+            self.payload,
+            self.soft_commit,
+        ))?;
+        block_on(self.index_writer.trigger_commit());
         Ok(self.opstamp)
     }
 }

src/indexer/resource_manager.rs

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

src/indexer/segment_entry.rs

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

src/indexer/segment_manager.rs

@@ -1,18 +1,16 @@
-use slog::{warn, Logger};
-
 use super::segment_register::SegmentRegister;
 use crate::core::SegmentId;
 use crate::core::SegmentMeta;
 use crate::error::TantivyError;
-use crate::indexer::delete_queue::DeleteCursor;
-use crate::indexer::SegmentEntry;
+use crate::indexer::{SegmentEntry, MergeOperationInventory, MergeCandidate, MergeOperation};
+use crate::{Segment, Opstamp};
 use std::collections::hash_set::HashSet;
 use std::fmt::{self, Debug, Formatter};
-use std::sync::RwLock;
+use std::sync::{Arc, RwLock};
 use std::sync::{RwLockReadGuard, RwLockWriteGuard};
 
 #[derive(Default)]
-struct SegmentRegisters {
+pub(crate) struct SegmentRegisters {
     uncommitted: SegmentRegister,
     committed: SegmentRegister,
 }
@@ -24,6 +22,17 @@ pub(crate) enum SegmentsStatus {
 }
 
 impl SegmentRegisters {
+    pub fn new(committed: SegmentRegister) -> SegmentRegisters {
+        SegmentRegisters {
+            uncommitted: Default::default(),
+            committed,
+        }
+    }
+
+    pub fn committed_segment(&self) -> Vec<Segment> {
+        self.committed.segments()
+    }
+
     /// Check if all the segments are committed or uncommited.
     ///
     /// If some segment is missing or segments are in a different state (this should not happen
@@ -44,9 +53,10 @@ impl SegmentRegisters {
 ///
 /// It guarantees the atomicity of the
 /// changes (merges especially)
+#[derive(Default)]
 pub struct SegmentManager {
-    registers: RwLock<SegmentRegisters>,
-    logger: Logger,
+    registers: Arc<RwLock<SegmentRegisters>>,
+    merge_operations: MergeOperationInventory,
 }
 
 impl Debug for SegmentManager {
@@ -60,36 +70,28 @@ impl Debug for SegmentManager {
     }
 }
 
-pub fn get_mergeable_segments(
-    in_merge_segment_ids: &HashSet<SegmentId>,
-    segment_manager: &SegmentManager,
-) -> (Vec<SegmentMeta>, Vec<SegmentMeta>) {
-    let registers_lock = segment_manager.read();
-    (
-        registers_lock
-            .committed
-            .get_mergeable_segments(in_merge_segment_ids),
-        registers_lock
-            .uncommitted
-            .get_mergeable_segments(in_merge_segment_ids),
-    )
-}
 
 impl SegmentManager {
-    pub fn from_segments(
-        segment_metas: Vec<SegmentMeta>,
-        delete_cursor: &DeleteCursor,
-        logger: Logger,
-    ) -> SegmentManager {
+    pub(crate) fn new(registers: Arc<RwLock<SegmentRegisters>>) -> SegmentManager {
         SegmentManager {
-            registers: RwLock::new(SegmentRegisters {
-                uncommitted: SegmentRegister::default(),
-                committed: SegmentRegister::new(segment_metas, delete_cursor),
-            }),
-            logger,
+            registers,
+            merge_operations: Default::default()
         }
     }
 
+    pub fn new_merge_operation(&self, opstamp: Opstamp, merge_candidate: MergeCandidate) -> MergeOperation {
+        MergeOperation::new(
+            &self.merge_operations,
+            opstamp,
+            merge_candidate.0
+
+        )
+    }
+
+    pub fn wait_merging_thread(&self) {
+        self.merge_operations.wait_until_empty()
+    }
+
     /// Returns all of the segment entries (committed or uncommitted)
     pub fn segment_entries(&self) -> Vec<SegmentEntry> {
         let registers_lock = self.read();
@@ -98,6 +100,34 @@ impl SegmentManager {
         segment_entries
     }
 
+    /// Returns the segments that are currently not in merge.
+    ///
+    /// They are split over two `Vec`. The committed segments on one hand
+    /// and the uncommitted ones on the other hand.
+    ///
+    /// This method is useful when searching for merge candidate or segments
+    /// to persists.
+    pub fn segments_not_in_merge(&self) -> (Vec<SegmentMeta>, Vec<SegmentMeta>) {
+        let in_merge_segment_ids: HashSet<SegmentId> = self.merge_operations.segment_in_merge();
+        let registers_lock = self.read();
+        (
+            registers_lock
+                .committed
+                .get_mergeable_segments(&in_merge_segment_ids),
+            registers_lock
+                .uncommitted
+                .get_mergeable_segments(&in_merge_segment_ids),
+        )
+    }
+
+    pub fn largest_segment_not_in_merge(&self) -> Option<SegmentMeta> {
+        let (committed, uncommitted) = self.segments_not_in_merge();
+        let mut segments = vec![];
+        segments.extend(committed);
+        segments.extend(uncommitted);
+        None
+    }
+
     // Lock poisoning should never happen :
     // The lock is acquired and released within this class,
     // and the operations cannot panic.
@@ -190,7 +220,7 @@ impl SegmentManager {
         let segments_status = registers_lock
             .segments_status(before_merge_segment_ids)
             .ok_or_else(|| {
-                warn!(self.logger, "couldn't find segment in SegmentManager");
+                warn!("couldn't find segment in SegmentManager");
                 crate::TantivyError::InvalidArgument(
                     "The segments that were merged could not be found in the SegmentManager. \
                      This is not necessarily a bug, and can happen after a rollback for instance."

src/indexer/segment_register.rs

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

src/indexer/segment_serializer.rs

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

src/indexer/segment_updater.rs

@@ -1,4 +1,4 @@
-use super::segment_manager::{get_mergeable_segments, SegmentManager};
+use super::segment_manager::SegmentManager;
 use crate::core::Index;
 use crate::core::IndexMeta;
 use crate::core::Segment;
@@ -7,25 +7,24 @@ use crate::core::SegmentMeta;
 use crate::core::SerializableSegment;
 use crate::core::META_FILEPATH;
 use crate::directory::{Directory, DirectoryClone, GarbageCollectionResult};
-use crate::indexer::delete_queue::DeleteCursor;
 use crate::indexer::index_writer::advance_deletes;
-use crate::indexer::merge_operation::MergeOperationInventory;
 use crate::indexer::merger::IndexMerger;
-use crate::indexer::segment_manager::SegmentsStatus;
+use crate::indexer::segment_manager::{SegmentRegisters, SegmentsStatus};
 use crate::indexer::stamper::Stamper;
 use crate::indexer::SegmentEntry;
 use crate::indexer::SegmentSerializer;
 use crate::indexer::{DefaultMergePolicy, MergePolicy};
 use crate::indexer::{MergeCandidate, MergeOperation};
 use crate::schema::Schema;
-use crate::Opstamp;
+use crate::{Opstamp, SegmentComponent};
 use futures::channel::oneshot;
 use futures::executor::{ThreadPool, ThreadPoolBuilder};
 use futures::future::Future;
 use futures::future::TryFutureExt;
-use slog::{debug, error, info, warn};
+use serde_json;
 use std::borrow::BorrowMut;
 use std::collections::HashSet;
+use std::io::Write;
 use std::ops::Deref;
 use std::path::PathBuf;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -65,11 +64,12 @@ pub fn save_new_metas(schema: Schema, directory: &mut dyn Directory) -> crate::R
 ///
 /// This method is not part of tantivy's public API
 fn save_metas(metas: &IndexMeta, directory: &mut dyn Directory) -> crate::Result<()> {
-    let mut meta_json = serde_json::to_string_pretty(metas)?;
+    info!("save metas");
+    let mut buffer = serde_json::to_vec_pretty(metas)?;
     // Just adding a new line at the end of the buffer.
-    meta_json.push_str("\n");
-    debug!(directory.logger(), "save meta"; "content"=>&meta_json);
-    directory.atomic_write(&META_FILEPATH, meta_json.as_bytes())?;
+    writeln!(&mut buffer)?;
+    directory.atomic_write(&META_FILEPATH, &buffer[..])?;
+    debug!("Saved metas {:?}", serde_json::to_string_pretty(&metas));
     Ok(())
 }
 
@@ -96,6 +96,7 @@ impl Deref for SegmentUpdater {
 async fn garbage_collect_files(
     segment_updater: SegmentUpdater,
 ) -> crate::Result<GarbageCollectionResult> {
+    info!("Running garbage collection");
     let mut index = segment_updater.index.clone();
     index
         .directory_mut()
@@ -105,36 +106,41 @@ async fn garbage_collect_files(
 /// Merges a list of segments the list of segment givens in the `segment_entries`.
 /// This function happens in the calling thread and is computationally expensive.
 fn merge(
-    merged_segment: Segment,
     index: &Index,
     mut segment_entries: Vec<SegmentEntry>,
     target_opstamp: Opstamp,
 ) -> crate::Result<SegmentEntry> {
-    // First we apply all of the delete to the merged segment, up to the target opstamp.
+    // first we need to apply deletes to our segment.
+    let mut merged_segment = index.new_segment();
+
+    // First we apply all of the delet to the merged segment, up to the target opstamp.
     for segment_entry in &mut segment_entries {
-        let segment = index.segment(segment_entry.meta().clone());
-        advance_deletes(segment, segment_entry, target_opstamp)?;
+        advance_deletes(segment_entry, target_opstamp)?;
     }
 
-    let delete_cursor = segment_entries[0].delete_cursor().clone();
+    let delete_cursor = segment_entries[0].delete_cursor();
 
     let segments: Vec<Segment> = segment_entries
         .iter()
-        .map(|segment_entry| index.segment(segment_entry.meta().clone()))
+        .map(|segment_entry| segment_entry.segment().clone())
         .collect();
 
     // An IndexMerger is like a "view" of our merged segments.
     let merger: IndexMerger = IndexMerger::open(index.schema(), &segments[..])?;
 
     // ... we just serialize this index merger in our new segment to merge the two segments.
-    let segment_serializer = SegmentSerializer::for_segment(merged_segment.clone())?;
+    let segment_serializer = SegmentSerializer::for_segment(&mut merged_segment)?;
 
-    let num_docs = merger.write(segment_serializer)?;
+    let store_wrt = merged_segment.open_write(SegmentComponent::STORE)?;
+    merger.write_storable_fields(store_wrt)?;
 
-    let merged_segment_id = merged_segment.id();
+    let max_doc = merger.write(segment_serializer)?;
 
-    let segment_meta = index.new_segment_meta(merged_segment_id, num_docs);
-    Ok(SegmentEntry::new(segment_meta, delete_cursor, None))
+    Ok(SegmentEntry::new(
+        merged_segment.with_max_doc(max_doc),
+        delete_cursor,
+        None,
+    ))
 }
 
 pub(crate) struct InnerSegmentUpdater {
@@ -153,18 +159,15 @@ pub(crate) struct InnerSegmentUpdater {
     merge_policy: RwLock<Arc<Box<dyn MergePolicy>>>,
     killed: AtomicBool,
     stamper: Stamper,
-    merge_operations: MergeOperationInventory,
 }
 
 impl SegmentUpdater {
     pub fn create(
+        segment_registers: Arc<RwLock<SegmentRegisters>>,
         index: Index,
         stamper: Stamper,
-        delete_cursor: &DeleteCursor,
     ) -> crate::Result<SegmentUpdater> {
-        let segments = index.searchable_segment_metas()?;
-        let segment_manager =
-            SegmentManager::from_segments(segments, delete_cursor, index.logger().clone());
+        let segment_manager = SegmentManager::new(segment_registers);
         let pool = ThreadPoolBuilder::new()
             .name_prefix("segment_updater")
             .pool_size(1)
@@ -193,7 +196,6 @@ impl SegmentUpdater {
             merge_policy: RwLock::new(Arc::new(Box::new(DefaultMergePolicy::default()))),
             killed: AtomicBool::new(false),
             stamper,
-            merge_operations: Default::default(),
         })))
     }
 
@@ -259,8 +261,7 @@ impl SegmentUpdater {
     fn purge_deletes(&self, target_opstamp: Opstamp) -> crate::Result<Vec<SegmentEntry>> {
         let mut segment_entries = self.segment_manager.segment_entries();
         for segment_entry in &mut segment_entries {
-            let segment = self.index.segment(segment_entry.meta().clone());
-            advance_deletes(segment, segment_entry, target_opstamp)?;
+            advance_deletes(segment_entry, target_opstamp)?;
         }
         Ok(segment_entries)
     }
@@ -328,12 +329,21 @@ impl SegmentUpdater {
         &self,
         opstamp: Opstamp,
         payload: Option<String>,
+        soft_commit: bool,
     ) -> impl Future<Output = crate::Result<()>> {
         let segment_updater: SegmentUpdater = self.clone();
+        let directory = self.index.directory().clone();
         self.schedule_future(async move {
-            let segment_entries = segment_updater.purge_deletes(opstamp)?;
+            let mut segment_entries = segment_updater.purge_deletes(opstamp)?;
+            if !soft_commit {
+                for segment_entry in &mut segment_entries {
+                    segment_entry.persist(directory.clone())?;
+                }
+            }
             segment_updater.segment_manager.commit(segment_entries);
-            segment_updater.save_metas(opstamp, payload)?;
+            if !soft_commit {
+                segment_updater.save_metas(opstamp, payload)?;
+            }
             let _ = garbage_collect_files(segment_updater.clone()).await;
             segment_updater.consider_merge_options().await;
             Ok(())
@@ -350,7 +360,7 @@ impl SegmentUpdater {
 
     pub(crate) fn make_merge_operation(&self, segment_ids: &[SegmentId]) -> MergeOperation {
         let commit_opstamp = self.load_metas().opstamp;
-        MergeOperation::new(&self.merge_operations, commit_opstamp, segment_ids.to_vec())
+        self.segment_manager.new_merge_operation(commit_opstamp, MergeCandidate(segment_ids.to_vec()))
     }
 
     // Starts a merge operation. This function will block until the merge operation is effectively
@@ -384,18 +394,7 @@ impl SegmentUpdater {
             .segment_manager
             .start_merge(merge_operation.segment_ids())?;
 
-        let segment_ids_str: String = merge_operation
-            .segment_ids()
-            .iter()
-            .map(|segment_id| segment_id.to_string())
-            .collect::<Vec<String>>()
-            .join(",");
-
-        let merged_segment = self.index.new_segment();
-        let logger = self.index.logger().new(slog::o!("segments"=>segment_ids_str, "merged-segment"=>merged_segment.id().to_string()));
-
-        let num_merges: usize = self.merge_operations.list().len();
-        slog::info!(&logger, "merge"; "stage"=>"start", "num-merges" => num_merges);
+        info!("Starting merge  - {:?}", merge_operation.segment_ids());
 
         let (merging_future_send, merging_future_recv) =
             oneshot::channel::<crate::Result<SegmentMeta>>();
@@ -406,20 +405,22 @@ impl SegmentUpdater {
             // as well as which segment is currently in merge and therefore should not be
             // candidate for another merge.
             match merge(
-                merged_segment,
                 &segment_updater.index,
                 segment_entries,
                 merge_operation.target_opstamp(),
             ) {
                 Ok(after_merge_segment_entry) => {
-                    info!(&logger, "merge"; "stage" => "end");
                     let segment_meta = segment_updater
                         .end_merge(merge_operation, after_merge_segment_entry)
                         .await;
                     let _send_result = merging_future_send.send(segment_meta);
                 }
                 Err(e) => {
-                    error!(&logger, "merge"; "stage" => "fail", "cause"=>e.to_string());
+                    warn!(
+                        "Merge of {:?} was cancelled: {:?}",
+                        merge_operation.segment_ids().to_vec(),
+                        e
+                    );
                     // ... cancel merge
                     if cfg!(test) {
                         panic!("Merge failed.");
@@ -433,9 +434,8 @@ impl SegmentUpdater {
     }
 
     async fn consider_merge_options(&self) {
-        let merge_segment_ids: HashSet<SegmentId> = self.merge_operations.segment_in_merge();
         let (committed_segments, uncommitted_segments) =
-            get_mergeable_segments(&merge_segment_ids, &self.segment_manager);
+            self.segment_manager.segments_not_in_merge();
 
         // Committed segments cannot be merged with uncommitted_segments.
         // We therefore consider merges using these two sets of segments independently.
@@ -446,7 +446,7 @@ impl SegmentUpdater {
             .compute_merge_candidates(&uncommitted_segments)
             .into_iter()
             .map(|merge_candidate| {
-                MergeOperation::new(&self.merge_operations, current_opstamp, merge_candidate.0)
+                self.segment_manager.new_merge_operation(current_opstamp, merge_candidate)
             })
             .collect();
 
@@ -455,17 +455,16 @@ impl SegmentUpdater {
             .compute_merge_candidates(&committed_segments)
             .into_iter()
             .map(|merge_candidate: MergeCandidate| {
-                MergeOperation::new(&self.merge_operations, commit_opstamp, merge_candidate.0)
+                self.segment_manager.new_merge_operation(commit_opstamp, merge_candidate)
             })
             .collect::<Vec<_>>();
         merge_candidates.extend(committed_merge_candidates.into_iter());
 
-        let logger = self.index.logger();
         for merge_operation in merge_candidates {
             if let Err(err) = self.start_merge(merge_operation) {
                 warn!(
-                    logger,
-                    "merge-start-fail (not fatal, not necessarily a problem)"; "reason" => format!("{}", err),
+                    "Starting the merge failed for the following reason. This is not fatal. {}",
+                    err
                 );
             }
         }
@@ -478,25 +477,17 @@ impl SegmentUpdater {
     ) -> impl Future<Output = crate::Result<SegmentMeta>> {
         let segment_updater = self.clone();
         let after_merge_segment_meta = after_merge_segment_entry.meta().clone();
-        let logger = self.index.logger().new(
-            slog::o!("segment"=>after_merge_segment_meta.id().to_string(),
-            "delete-opstamp"=>after_merge_segment_meta.delete_opstamp()),
-        );
         let end_merge_future = self.schedule_future(async move {
+            info!("End merge {:?}", after_merge_segment_entry.meta());
             {
-                let mut delete_cursor = after_merge_segment_entry.delete_cursor().clone();
+                let mut delete_cursor = after_merge_segment_entry.delete_cursor();
                 if let Some(delete_operation) = delete_cursor.get() {
                     let committed_opstamp = segment_updater.load_metas().opstamp;
                     if delete_operation.opstamp < committed_opstamp {
-                        let index = &segment_updater.index;
-                        let segment = index.segment(after_merge_segment_entry.meta().clone());
-                        if let Err(e) = advance_deletes(
-                            segment,
-                            &mut after_merge_segment_entry,
-                            committed_opstamp,
-                        ) {
+                        if let Err(e) =
+                            advance_deletes(&mut after_merge_segment_entry, committed_opstamp)
+                        {
                             error!(
-                                logger,
                                 "Merge of {:?} was cancelled (advancing deletes failed): {:?}",
                                 merge_operation.segment_ids(),
                                 e
@@ -533,7 +524,7 @@ impl SegmentUpdater {
     ///
     /// Upon termination of the current merging threads,
     /// merge opportunity may appear.
-    ///
+    //
     /// We keep waiting until the merge policy judges that
     /// no opportunity is available.
     ///
@@ -544,9 +535,8 @@ impl SegmentUpdater {
     ///
     /// Obsolete files will eventually be cleaned up
     /// by the directory garbage collector.
-    pub fn wait_merging_thread(&self) -> crate::Result<()> {
-        self.merge_operations.wait_until_empty();
-        Ok(())
+    pub fn wait_merging_thread(&self) {
+        self.segment_manager.wait_merging_thread()
     }
 }
 
@@ -555,7 +545,8 @@ mod tests {
 
     use crate::indexer::merge_policy::tests::MergeWheneverPossible;
     use crate::schema::*;
-    use crate::Index;
+    use crate::{Index, SegmentId};
+    use futures::executor::block_on;
 
     #[test]
     fn test_delete_during_merge() {
@@ -566,7 +557,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
 
         // writing the segment
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         index_writer.set_merge_policy(Box::new(MergeWheneverPossible));
 
         {
@@ -619,7 +610,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
 
         // writing the segment
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
 
         {
             for _ in 0..100 {
@@ -690,7 +681,7 @@ mod tests {
         let index = Index::create_in_ram(schema);
 
         // writing the segment
-        let mut index_writer = index.writer_for_tests().unwrap();
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
 
         {
             for _ in 0..100 {
@@ -706,4 +697,27 @@ mod tests {
             .segment_entries();
         assert!(seg_vec.is_empty());
     }
+
+    #[test]
+    fn test_merge_over_soft_commit() {
+        let mut schema_builder = Schema::builder();
+        let text_field = schema_builder.add_text_field("text", TEXT);
+        let schema = schema_builder.build();
+        let index = Index::create_in_ram(schema);
+        // writing the segment
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(text_field=>"a"));
+        assert!(index_writer.soft_commit().is_ok());
+        index_writer.add_document(doc!(text_field=>"a"));
+        assert!(index_writer.soft_commit().is_ok());
+
+        let reader = index_writer.reader(1).unwrap();
+        let segment_ids: Vec<SegmentId> = reader
+            .searcher()
+            .segment_readers()
+            .iter()
+            .map(|reader| reader.segment_id())
+            .collect();
+        assert!(block_on(index_writer.merge(&segment_ids)).is_ok());
+    }
 }

src/indexer/segment_writer.rs

@@ -1,8 +1,11 @@
 use super::operation::AddOperation;
+use crate::core::Segment;
 use crate::core::SerializableSegment;
+use crate::directory::{SpillingResult, SpillingWriter, TerminatingWrite};
 use crate::fastfield::FastFieldsWriter;
-use crate::fieldnorm::{FieldNormReaders, FieldNormsWriter};
+use crate::fieldnorm::FieldNormsWriter;
 use crate::indexer::segment_serializer::SegmentSerializer;
+use crate::indexer::IndexWriterConfig;
 use crate::postings::compute_table_size;
 use crate::postings::MultiFieldPostingsWriter;
 use crate::schema::FieldType;
@@ -10,21 +13,24 @@ use crate::schema::Schema;
 use crate::schema::Term;
 use crate::schema::Value;
 use crate::schema::{Field, FieldEntry};
+use crate::store::StoreWriter;
 use crate::tokenizer::{BoxTokenStream, PreTokenizedStream};
-use crate::tokenizer::{FacetTokenizer, TextAnalyzer};
+use crate::tokenizer::{FacetTokenizer, TextAnalyzer, TokenizerManager};
 use crate::tokenizer::{TokenStreamChain, Tokenizer};
 use crate::Opstamp;
-use crate::{core::Segment, tokenizer::MAX_TOKEN_LEN};
 use crate::{DocId, SegmentComponent};
 use std::io;
+use std::io::Write;
+use std::str;
+use crate::indexer::resource_manager::ResourceManager;
 
 /// Computes the initial size of the hash table.
 ///
 /// Returns a number of bit `b`, such that the recommended initial table size is 2^b.
-fn initial_table_size(per_thread_memory_budget: usize) -> crate::Result<usize> {
-    let table_memory_upper_bound = per_thread_memory_budget / 3;
+fn initial_table_size(per_thread_memory_budget: u64) -> crate::Result<usize> {
+    let table_memory_upper_bound = per_thread_memory_budget / 3u64;
     if let Some(limit) = (10..)
-        .take_while(|num_bits: &usize| compute_table_size(*num_bits) < table_memory_upper_bound)
+        .take_while(|num_bits| compute_table_size(*num_bits) < table_memory_upper_bound)
         .last()
     {
         Ok(limit.min(19)) // we cap it at 2^19 = 512K.
@@ -42,12 +48,13 @@ fn initial_table_size(per_thread_memory_budget: usize) -> crate::Result<usize> {
 pub struct SegmentWriter {
     max_doc: DocId,
     multifield_postings: MultiFieldPostingsWriter,
-    segment_serializer: SegmentSerializer,
+    segment: Segment,
     fast_field_writers: FastFieldsWriter,
     fieldnorms_writer: FieldNormsWriter,
     doc_opstamps: Vec<Opstamp>,
     tokenizers: Vec<Option<TextAnalyzer>>,
-    term_buffer: Term,
+    store_writer: StoreWriter<SpillingWriter>,
+    memory_manager: ResourceManager,
 }
 
 impl SegmentWriter {
@@ -61,13 +68,13 @@ impl SegmentWriter {
     /// - segment: The segment being written
     /// - schema
     pub fn for_segment(
-        memory_budget: usize,
+        config: &IndexWriterConfig,
         segment: Segment,
         schema: &Schema,
+        tokenizer_manager: &TokenizerManager,
+        memory_manager: ResourceManager
     ) -> crate::Result<SegmentWriter> {
-        let tokenizer_manager = segment.index().tokenizers().clone();
-        let table_num_bits = initial_table_size(memory_budget)?;
-        let segment_serializer = SegmentSerializer::for_segment(segment)?;
+        let table_num_bits = initial_table_size(config.heap_size_in_byte_per_thread())?;
         let multifield_postings = MultiFieldPostingsWriter::new(schema, table_num_bits);
         let tokenizers = schema
             .fields()
@@ -83,15 +90,26 @@ impl SegmentWriter {
                 },
             )
             .collect();
+        let mut segment_clone = segment.clone();
+        let spilling_wrt = SpillingWriter::new(
+            50_000_000,
+            Box::new(move || {
+                segment_clone
+                    .open_write(SegmentComponent::STORE)
+                    .map_err(|err| io::Error::new(io::ErrorKind::Other, err))
+            }),
+        );
+        let store_writer = StoreWriter::new(spilling_wrt);
         Ok(SegmentWriter {
             max_doc: 0,
             multifield_postings,
             fieldnorms_writer: FieldNormsWriter::for_schema(schema),
-            segment_serializer,
+            segment,
             fast_field_writers: FastFieldsWriter::from_schema(schema),
             doc_opstamps: Vec::with_capacity(1_000),
             tokenizers,
-            term_buffer: Term::new(),
+            store_writer,
+            memory_manager
         })
     }
 
@@ -99,18 +117,33 @@ impl SegmentWriter {
     ///
     /// Finalize consumes the `SegmentWriter`, so that it cannot
     /// be used afterwards.
-    pub fn finalize(mut self) -> crate::Result<Vec<u64>> {
+    pub fn finalize(mut self) -> crate::Result<(Segment, Vec<u64>)> {
         self.fieldnorms_writer.fill_up_to_max_doc(self.max_doc);
+        let spilling_wrt = self.store_writer.close()?;
+        let mut segment: Segment;
+        match spilling_wrt.finalize()? {
+            SpillingResult::Spilled => {
+                segment = self.segment.clone();
+            }
+            SpillingResult::Buffer(buf) => {
+                segment = self.segment.into_volatile(self.memory_manager.clone());
+                let mut store_wrt = segment.open_write(SegmentComponent::STORE)?;
+                store_wrt.write_all(&buf[..])?;
+                store_wrt.terminate()?;
+            }
+        }
+        let segment_serializer = SegmentSerializer::for_segment(&mut segment)?;
+        segment = segment.with_max_doc(self.max_doc);
         write(
             &self.multifield_postings,
             &self.fast_field_writers,
             &self.fieldnorms_writer,
-            self.segment_serializer,
+            segment_serializer,
         )?;
-        Ok(self.doc_opstamps)
+        Ok((segment, self.doc_opstamps))
     }
 
-    pub fn mem_usage(&self) -> usize {
+    pub fn mem_usage(&self) -> u64 {
         self.multifield_postings.mem_usage()
     }
 
@@ -129,29 +162,24 @@ impl SegmentWriter {
             if !field_options.is_indexed() {
                 continue;
             }
-            let (term_buffer, multifield_postings) =
-                (&mut self.term_buffer, &mut self.multifield_postings);
             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");
-                                }
-                            });
+                    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(fake_str).process(&mut |token| {
-                            if token.text.len() > MAX_TOKEN_LEN {
-                                return;
-                            }
-                            term_buffer.set_text(&token.text);
+                            term.set_text(&token.text);
                             let unordered_term_id =
-                                multifield_postings.subscribe(doc_id, &term_buffer);
+                                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 {
@@ -174,6 +202,7 @@ impl SegmentWriter {
                                 if let Some(last_token) = tok_str.tokens.last() {
                                     total_offset += last_token.offset_to;
                                 }
+
                                 token_streams
                                     .push(PreTokenizedStream::from(tok_str.clone()).into());
                             }
@@ -183,6 +212,7 @@ impl SegmentWriter {
                                 {
                                     offsets.push(total_offset);
                                     total_offset += text.len();
+
                                     token_streams.push(tokenizer.token_stream(text));
                                 }
                             }
@@ -194,12 +224,8 @@ impl SegmentWriter {
                         0
                     } else {
                         let mut token_stream = TokenStreamChain::new(offsets, token_streams);
-                        multifield_postings.index_text(
-                            doc_id,
-                            field,
-                            &mut token_stream,
-                            term_buffer,
-                        )
+                        self.multifield_postings
+                            .index_text(doc_id, field, &mut token_stream)
                     };
 
                     self.fieldnorms_writer.record(doc_id, field, num_tokens);
@@ -207,36 +233,44 @@ impl SegmentWriter {
                 FieldType::U64(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
-                            term_buffer.set_u64(field_value.value().u64_value());
-                            multifield_postings.subscribe(doc_id, &term_buffer);
+                            let term = Term::from_field_u64(
+                                field_value.field(),
+                                field_value.value().u64_value(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
                         }
                     }
                 }
                 FieldType::Date(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
-                            term_buffer.set_i64(field_value.value().date_value().timestamp());
-                            multifield_postings.subscribe(doc_id, &term_buffer);
+                            let term = Term::from_field_i64(
+                                field_value.field(),
+                                field_value.value().date_value().timestamp(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
                         }
                     }
                 }
                 FieldType::I64(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
-                            term_buffer.set_i64(field_value.value().i64_value());
-                            multifield_postings.subscribe(doc_id, &term_buffer);
+                            let term = Term::from_field_i64(
+                                field_value.field(),
+                                field_value.value().i64_value(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
                         }
                     }
                 }
                 FieldType::F64(ref int_option) => {
                     if int_option.is_indexed() {
                         for field_value in field_values {
-                            term_buffer.set_field(field_value.field());
-                            term_buffer.set_f64(field_value.value().f64_value());
-                            multifield_postings.subscribe(doc_id, &term_buffer);
+                            let term = Term::from_field_f64(
+                                field_value.field(),
+                                field_value.value().f64_value(),
+                            );
+                            self.multifield_postings.subscribe(doc_id, &term);
                         }
                     }
                 }
@@ -247,8 +281,7 @@ impl SegmentWriter {
         }
         doc.filter_fields(|field| schema.get_field_entry(field).is_stored());
         doc.prepare_for_store();
-        let doc_writer = self.segment_serializer.get_store_writer();
-        doc_writer.store(&doc)?;
+        self.store_writer.store(&doc)?;
         self.max_doc += 1;
         Ok(())
     }
@@ -281,16 +314,9 @@ fn write(
     fieldnorms_writer: &FieldNormsWriter,
     mut serializer: SegmentSerializer,
 ) -> crate::Result<()> {
-    if let Some(fieldnorms_serializer) = serializer.extract_fieldnorms_serializer() {
-        fieldnorms_writer.serialize(fieldnorms_serializer)?;
-    }
-    let fieldnorm_data = serializer
-        .segment()
-        .open_read(SegmentComponent::FIELDNORMS)?;
-    let fieldnorm_readers = FieldNormReaders::open(fieldnorm_data)?;
-    let term_ord_map =
-        multifield_postings.serialize(serializer.get_postings_serializer(), fieldnorm_readers)?;
+    let term_ord_map = multifield_postings.serialize(serializer.get_postings_serializer())?;
     fast_field_writers.serialize(serializer.get_fast_field_serializer(), &term_ord_map)?;
+    fieldnorms_writer.serialize(serializer.get_fieldnorms_serializer())?;
     serializer.close()?;
     Ok(())
 }

src/lib.rs

@@ -102,7 +102,10 @@
 extern crate serde_json;
 
 #[macro_use]
-extern crate thiserror;
+extern crate log;
+
+#[macro_use]
+extern crate failure;
 
 #[cfg(all(test, feature = "unstable"))]
 extern crate test;
@@ -145,7 +148,6 @@ pub mod schema;
 pub mod space_usage;
 pub mod store;
 pub mod termdict;
-pub use slog;
 
 mod reader;
 
@@ -154,14 +156,14 @@ mod snippet;
 pub use self::snippet::{Snippet, SnippetGenerator};
 
 mod docset;
-pub use self::docset::{DocSet, TERMINATED};
+pub use self::docset::{DocSet, SkipResult};
 pub use crate::common::{f64_to_u64, i64_to_u64, u64_to_f64, u64_to_i64};
 pub use crate::core::{Executor, SegmentComponent};
 pub use crate::core::{Index, IndexMeta, Searcher, Segment, SegmentId, SegmentMeta};
 pub use crate::core::{InvertedIndexReader, SegmentReader};
 pub use crate::directory::Directory;
 pub use crate::indexer::operation::UserOperation;
-pub use crate::indexer::IndexWriter;
+pub use crate::indexer::{IndexWriter, IndexWriterConfig};
 pub use crate::postings::Postings;
 pub use crate::reader::LeasedItem;
 pub use crate::schema::{Document, Term};
@@ -171,7 +173,7 @@ use once_cell::sync::Lazy;
 use serde::{Deserialize, Serialize};
 
 /// Index format version.
-const INDEX_FORMAT_VERSION: u32 = 2;
+const INDEX_FORMAT_VERSION: u32 = 1;
 
 /// Structure version for the index.
 #[derive(Clone, PartialEq, Eq, Serialize, Deserialize)]
@@ -243,10 +245,11 @@ pub type DocId = u32;
 /// with opstamp `n+1`.
 pub type Opstamp = u64;
 
-/// A Score that represents the relevance of the document to the query
+/// A f32 that represents the relevance of the document to the query
 ///
-/// This is modelled internally as a `f32`. The larger the number, the more relevant
-/// the document to the search query.
+/// This is modelled internally as a `f32`. The
+/// larger the number, the more relevant the document
+/// to the search
 pub type Score = f32;
 
 /// A `SegmentLocalId` identifies a segment.
@@ -279,13 +282,15 @@ pub struct DocAddress(pub SegmentLocalId, pub DocId);
 
 #[cfg(test)]
 mod tests {
+
     use crate::collector::tests::TEST_COLLECTOR_WITH_SCORE;
     use crate::core::SegmentReader;
-    use crate::docset::{DocSet, TERMINATED};
+    use crate::docset::DocSet;
     use crate::query::BooleanQuery;
     use crate::schema::*;
     use crate::DocAddress;
     use crate::Index;
+    use crate::IndexWriter;
     use crate::Postings;
     use crate::ReloadPolicy;
     use rand::distributions::Bernoulli;
@@ -293,26 +298,17 @@ mod tests {
     use rand::rngs::StdRng;
     use rand::{Rng, SeedableRng};
 
-    /// Checks if left and right are close one to each other.
-    /// Panics if the two values are more than 0.5% apart.
-    #[macro_export]
-    macro_rules! assert_nearly_equals {
-        ($left:expr, $right:expr) => {{
-            match (&$left, &$right) {
-                (left_val, right_val) => {
-                    let diff = (left_val - right_val).abs();
-                    let add = left_val.abs() + right_val.abs();
-                    if diff > 0.0005 * add {
-                        panic!(
-                            r#"assertion failed: `(left ~= right)`
-  left: `{:?}`,
- right: `{:?}`"#,
-                            &*left_val, &*right_val
-                        )
-                    }
-                }
-            }
-        }};
+    pub fn assert_nearly_equals(expected: f32, val: f32) {
+        assert!(
+            nearly_equals(val, expected),
+            "Got {}, expected {}.",
+            val,
+            expected
+        );
+    }
+
+    pub fn nearly_equals(a: f32, b: f32) -> bool {
+        (a - b).abs() < 0.0005 * (a + b).abs()
     }
 
     pub fn generate_nonunique_unsorted(max_value: u32, n_elems: usize) -> Vec<u32> {
@@ -350,14 +346,14 @@ mod tests {
 
     #[test]
     #[cfg(feature = "mmap")]
-    fn test_indexing() -> crate::Result<()> {
+    fn test_indexing() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
         let index = Index::create_from_tempdir(schema).unwrap();
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             {
                 let doc = doc!(text_field=>"af b");
                 index_writer.add_document(doc);
@@ -372,30 +368,36 @@ mod tests {
             }
             assert!(index_writer.commit().is_ok());
         }
-        Ok(())
     }
 
     #[test]
-    fn test_docfreq1() -> crate::Result<()> {
+    fn test_docfreq1() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let index = Index::create_in_ram(schema_builder.build());
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
         {
             index_writer.add_document(doc!(text_field=>"a b c"));
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
         }
         {
-            index_writer.add_document(doc!(text_field=>"a"));
-            index_writer.add_document(doc!(text_field=>"a a"));
-            index_writer.commit()?;
+            {
+                let doc = doc!(text_field=>"a");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field=>"a a");
+                index_writer.add_document(doc);
+            }
+            index_writer.commit().unwrap();
         }
         {
-            index_writer.add_document(doc!(text_field=>"c"));
-            index_writer.commit()?;
+            let doc = doc!(text_field=>"c");
+            index_writer.add_document(doc);
+            index_writer.commit().unwrap();
         }
         {
-            let reader = index.reader()?;
+            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);
@@ -406,65 +408,80 @@ mod tests {
             let term_d = Term::from_field_text(text_field, "d");
             assert_eq!(searcher.doc_freq(&term_d), 0);
         }
-        Ok(())
     }
 
     #[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 {
-        let mut doc = docset.advance();
-        while doc != TERMINATED {
-            if !reader.is_deleted(doc) {
+        while docset.advance() {
+            if !reader.is_deleted(docset.doc()) {
                 return true;
             }
-            doc = docset.advance();
         }
         false
     }
 
     #[test]
-    fn test_delete_postings1() -> crate::Result<()> {
+    fn test_delete_postings1() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let term_abcd = Term::from_field_text(text_field, "abcd");
@@ -480,7 +497,7 @@ mod tests {
             .unwrap();
         {
             // writing the segment
-            let mut index_writer = index.writer_for_tests()?;
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
             // 0
             index_writer.add_document(doc!(text_field=>"a b"));
             // 1
@@ -496,10 +513,10 @@ 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);
@@ -527,15 +544,15 @@ 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());
@@ -564,15 +581,15 @@ 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());
@@ -604,20 +621,19 @@ mod tests {
                 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
@@ -625,23 +641,23 @@ mod tests {
             .inverted_index(term.field())
             .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
+        assert!(postings.advance());
         assert_eq!(postings.doc(), 0);
-        assert_eq!(postings.advance(), TERMINATED);
-        Ok(())
+        assert!(!postings.advance());
     }
 
     #[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
@@ -649,23 +665,23 @@ mod tests {
             .inverted_index(term.field())
             .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
+        assert!(postings.advance());
         assert_eq!(postings.doc(), 0);
-        assert_eq!(postings.advance(), TERMINATED);
-        Ok(())
+        assert!(!postings.advance());
     }
 
     #[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
@@ -673,31 +689,29 @@ mod tests {
             .inverted_index(term.field())
             .read_postings(&term, IndexRecordOption::Basic)
             .unwrap();
+        assert!(postings.advance());
         assert_eq!(postings.doc(), 0);
-        assert_eq!(postings.advance(), TERMINATED);
-        Ok(())
+        assert!(!postings.advance());
     }
 
     #[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); //< should not panic
-        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();
@@ -705,40 +719,55 @@ 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);
@@ -750,67 +779,68 @@ mod tests {
             let mut postings = inverted_index
                 .read_postings(&term_af, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
+            assert!(postings.advance());
             assert_eq!(postings.doc(), 0);
             assert_eq!(postings.term_freq(), 3);
-            assert_eq!(postings.advance(), TERMINATED);
+            assert!(!postings.advance());
         }
-        Ok(())
     }
 
     #[test]
-    fn test_searcher_1() -> crate::Result<()> {
+    fn test_searcher_1() {
         let mut schema_builder = Schema::builder();
         let text_field = schema_builder.add_text_field("text", TEXT);
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let reader = index.reader()?;
-        // 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();
@@ -818,17 +848,19 @@ mod tests {
         let reader = index
             .reader_builder()
             .reload_policy(ReloadPolicy::Manual)
-            .try_into()?;
+            .try_into()
+            .unwrap();
         assert_eq!(reader.searcher().num_docs(), 0u64);
-        // writing the segment
-        let mut index_writer = index.writer_for_tests()?;
-        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]
@@ -850,7 +882,7 @@ mod tests {
     }
 
     #[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);
@@ -860,14 +892,14 @@ mod tests {
         let schema = schema_builder.build();
 
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 50_000_000).unwrap();
         {
             let document =
                 doc!(fast_field_unsigned => 4u64, fast_field_signed=>4i64, fast_field_float=>4f64);
             index_writer.add_document(document);
-            index_writer.commit()?;
+            index_writer.commit().unwrap();
         }
-        let reader = index.reader()?;
+        let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let segment_reader: &SegmentReader = searcher.segment_reader(0);
         {
@@ -906,12 +938,11 @@ mod tests {
             let fast_field_reader = fast_field_reader_opt.unwrap();
             assert_eq!(fast_field_reader.get(0), 4f64)
         }
-        Ok(())
     }
 
     // motivated by #729
     #[test]
-    fn test_update_via_delete_insert() -> crate::Result<()> {
+    fn test_update_via_delete_insert() {
         use crate::collector::Count;
         use crate::indexer::NoMergePolicy;
         use crate::query::AllQuery;
@@ -925,17 +956,17 @@ mod tests {
         let schema = schema_builder.build();
 
         let index = Index::create_in_ram(schema.clone());
-        let index_reader = index.reader()?;
+        let index_reader = index.reader().unwrap();
 
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer(3_000_000).unwrap();
         index_writer.set_merge_policy(Box::new(NoMergePolicy));
 
         for doc_id in 0u64..DOC_COUNT {
             index_writer.add_document(doc!(id => doc_id));
         }
-        index_writer.commit()?;
+        index_writer.commit().unwrap();
 
-        index_reader.reload()?;
+        index_reader.reload().unwrap();
         let searcher = index_reader.searcher();
 
         assert_eq!(
@@ -946,11 +977,12 @@ mod tests {
         // update the 10 elements by deleting and re-adding
         for doc_id in 0u64..DOC_COUNT {
             index_writer.delete_term(Term::from_field_u64(id, doc_id));
-            index_writer.commit()?;
-            index_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!(
@@ -959,7 +991,7 @@ mod tests {
             );
         }
 
-        index_reader.reload()?;
+        index_reader.reload().unwrap();
         let searcher = index_reader.searcher();
         let segment_ids: Vec<SegmentId> = searcher
             .segment_readers()
@@ -968,18 +1000,12 @@ mod tests {
             .collect();
         block_on(index_writer.merge(&segment_ids)).unwrap();
 
-        index_reader.reload()?;
+        index_reader.reload().unwrap();
         let searcher = index_reader.searcher();
-        assert_eq!(searcher.search(&AllQuery, &Count)?, DOC_COUNT as usize);
-        Ok(())
-    }
 
-    #[test]
-    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

@@ -37,9 +37,9 @@ const LONG_SKIP_INTERVAL: u64 = (LONG_SKIP_IN_BLOCKS * COMPRESSION_BLOCK_SIZE) a
 #[cfg(test)]
 pub mod tests {
 
-    use super::PositionSerializer;
+    use super::{PositionReader, PositionSerializer};
     use crate::directory::ReadOnlySource;
-    use crate::positions::reader::PositionReader;
+    use crate::positions::COMPRESSION_BLOCK_SIZE;
     use std::iter;
 
     fn create_stream_buffer(vals: &[u32]) -> (ReadOnlySource, ReadOnlySource) {
@@ -68,7 +68,7 @@ pub mod tests {
         let mut position_reader = PositionReader::new(stream, skip, 0u64);
         for &n in &[1, 10, 127, 128, 130, 312] {
             let mut v = vec![0u32; n];
-            position_reader.read(0, &mut v[..]);
+            position_reader.read(&mut v[..n]);
             for i in 0..n {
                 assert_eq!(v[i], i as u32);
             }
@@ -76,19 +76,19 @@ pub mod tests {
     }
 
     #[test]
-    fn test_position_read_with_offset() {
-        let v: Vec<u32> = (0..1000).collect();
+    fn test_position_skip() {
+        let v: Vec<u32> = (0..1_000).collect();
         let (stream, skip) = create_stream_buffer(&v[..]);
         assert_eq!(skip.len(), 12);
         assert_eq!(stream.len(), 1168);
+
         let mut position_reader = PositionReader::new(stream, skip, 0u64);
-        for &offset in &[1u64, 10u64, 127u64, 128u64, 130u64, 312u64] {
-            for &len in &[1, 10, 130, 500] {
-                let mut v = vec![0u32; len];
-                position_reader.read(offset, &mut v[..]);
-                for i in 0..len {
-                    assert_eq!(v[i], i as u32 + offset as u32);
-                }
+        position_reader.skip(10);
+        for &n in &[10, 127, COMPRESSION_BLOCK_SIZE, 130, 312] {
+            let mut v = vec![0u32; n];
+            position_reader.read(&mut v[..n]);
+            for i in 0..n {
+                assert_eq!(v[i], 10u32 + i as u32);
             }
         }
     }
@@ -103,12 +103,11 @@ pub mod tests {
         let mut position_reader = PositionReader::new(stream, skip, 0u64);
         let mut buf = [0u32; 7];
         let mut c = 0;
-
-        let mut offset = 0;
         for _ in 0..100 {
-            position_reader.read(offset, &mut buf);
-            position_reader.read(offset, &mut buf);
-            offset += 7;
+            position_reader.read(&mut buf);
+            position_reader.read(&mut buf);
+            position_reader.skip(4);
+            position_reader.skip(3);
             for &el in &buf {
                 assert_eq!(c, el);
                 c += 1;
@@ -116,58 +115,6 @@ pub mod tests {
         }
     }
 
-    #[test]
-    fn test_position_reread_anchor_different_than_block() {
-        let v: Vec<u32> = (0..2_000_000).collect();
-        let (stream, skip) = create_stream_buffer(&v[..]);
-        assert_eq!(skip.len(), 15_749);
-        assert_eq!(stream.len(), 4_987_872);
-        let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), 0);
-        let mut buf = [0u32; 256];
-        position_reader.read(128, &mut buf);
-        for i in 0..256 {
-            assert_eq!(buf[i], (128 + i) as u32);
-        }
-        position_reader.read(128, &mut buf);
-        for i in 0..256 {
-            assert_eq!(buf[i], (128 + i) as u32);
-        }
-    }
-
-    #[test]
-    #[should_panic(expected = "offset arguments should be increasing.")]
-    fn test_position_panic_if_called_previous_anchor() {
-        let v: Vec<u32> = (0..2_000_000).collect();
-        let (stream, skip) = create_stream_buffer(&v[..]);
-        assert_eq!(skip.len(), 15_749);
-        assert_eq!(stream.len(), 4_987_872);
-        let mut buf = [0u32; 1];
-        let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), 200_000);
-        position_reader.read(230, &mut buf);
-        position_reader.read(9, &mut buf);
-    }
-
-    #[test]
-    fn test_positions_bug() {
-        let mut v: Vec<u32> = vec![];
-        for i in 1..200 {
-            for j in 0..i {
-                v.push(j);
-            }
-        }
-        let (stream, skip) = create_stream_buffer(&v[..]);
-        let mut buf = Vec::new();
-        let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), 0);
-        let mut offset = 0;
-        for i in 1..24 {
-            buf.resize(i, 0);
-            position_reader.read(offset, &mut buf[..]);
-            offset += i as u64;
-            let r: Vec<u32> = (0..i).map(|el| el as u32).collect();
-            assert_eq!(buf, &r[..]);
-        }
-    }
-
     #[test]
     fn test_position_long_skip_const() {
         const CONST_VAL: u32 = 9u32;
@@ -177,7 +124,7 @@ pub mod tests {
         assert_eq!(stream.len(), 1_000_000);
         let mut position_reader = PositionReader::new(stream, skip, 128 * 1024);
         let mut buf = [0u32; 1];
-        position_reader.read(0, &mut buf);
+        position_reader.read(&mut buf);
         assert_eq!(buf[0], CONST_VAL);
     }
 
@@ -196,7 +143,7 @@ pub mod tests {
         ] {
             let mut position_reader = PositionReader::new(stream.clone(), skip.clone(), offset);
             let mut buf = [0u32; 1];
-            position_reader.read(0, &mut buf);
+            position_reader.read(&mut buf);
             assert_eq!(buf[0], offset as u32);
         }
     }

src/positions/reader.rs

@@ -3,6 +3,7 @@ use crate::directory::ReadOnlySource;
 use crate::positions::COMPRESSION_BLOCK_SIZE;
 use crate::positions::LONG_SKIP_INTERVAL;
 use crate::positions::LONG_SKIP_IN_BLOCKS;
+use crate::postings::compression::compressed_block_size;
 /// Positions works as a long sequence of compressed block.
 /// All terms are chained one after the other.
 ///
@@ -61,34 +62,74 @@ impl Positions {
 
     fn reader(&self, offset: u64) -> PositionReader {
         let long_skip_id = (offset / LONG_SKIP_INTERVAL) as usize;
+        let small_skip = (offset % LONG_SKIP_INTERVAL) as usize;
         let offset_num_bytes: u64 = self.long_skip(long_skip_id);
         let 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 {
+        let mut position_reader = PositionReader {
             bit_packer: self.bit_packer,
             skip_read,
             position_read,
+            inner_offset: 0,
             buffer: Box::new([0u32; 128]),
-            block_offset: std::i64::MAX as u64,
-            anchor_offset: (long_skip_id as u64) * LONG_SKIP_INTERVAL,
-            abs_offset: offset,
-        }
+            ahead: None,
+        };
+        position_reader.skip(small_skip);
+        position_reader
     }
 }
 
-#[derive(Clone)]
 pub struct PositionReader {
     skip_read: OwnedRead,
     position_read: OwnedRead,
     bit_packer: BitPacker4x,
-    buffer: Box<[u32; COMPRESSION_BLOCK_SIZE]>,
+    inner_offset: usize,
+    buffer: Box<[u32; 128]>,
+    ahead: Option<usize>, // if None, no block is loaded.
+                          // if Some(num_blocks), the block currently loaded is num_blocks ahead
+                          // of the block of the next int to read.
+}
 
-    block_offset: u64,
-    anchor_offset: u64,
-
-    abs_offset: u64,
+// `ahead` represents the offset of the block currently loaded
+// compared to the cursor of the actual stream.
+//
+// By contract, when this function is called, the current block has to be
+// decompressed.
+//
+// If the requested number of els ends exactly at a given block, the next
+// block is not decompressed.
+fn read_impl(
+    bit_packer: BitPacker4x,
+    mut position: &[u8],
+    buffer: &mut [u32; 128],
+    mut inner_offset: usize,
+    num_bits: &[u8],
+    output: &mut [u32],
+) -> usize {
+    let mut output_start = 0;
+    let mut output_len = output.len();
+    let mut ahead = 0;
+    loop {
+        let available_len = COMPRESSION_BLOCK_SIZE - inner_offset;
+        // We have enough elements in the current block.
+        // Let's copy the requested elements in the output buffer,
+        // and return.
+        if output_len <= available_len {
+            output[output_start..].copy_from_slice(&buffer[inner_offset..][..output_len]);
+            return ahead;
+        }
+        output[output_start..][..available_len].copy_from_slice(&buffer[inner_offset..]);
+        output_len -= available_len;
+        output_start += available_len;
+        inner_offset = 0;
+        let num_bits = num_bits[ahead];
+        bit_packer.decompress(position, &mut buffer[..], num_bits);
+        let block_len = compressed_block_size(num_bits);
+        position = &position[block_len..];
+        ahead += 1;
+    }
 }
 
 impl PositionReader {
@@ -100,65 +141,57 @@ impl PositionReader {
         Positions::new(position_source, skip_source).reader(offset)
     }
 
-    fn advance_num_blocks(&mut self, num_blocks: usize) {
-        let num_bits: usize = self.skip_read.as_ref()[..num_blocks]
-            .iter()
-            .cloned()
-            .map(|num_bits| num_bits as usize)
-            .sum();
-        let num_bytes_to_skip = num_bits * COMPRESSION_BLOCK_SIZE / 8;
-        self.skip_read.advance(num_blocks as usize);
-        self.position_read.advance(num_bytes_to_skip);
-    }
-
-    /// Fills a buffer with the positions `[offset..offset+output.len())` integers.
-    ///
-    /// `offset` is required to have a value >= to the offsets given in previous calls
-    /// for the given `PositionReaderAbsolute` instance.
-    pub fn read(&mut self, mut offset: u64, mut output: &mut [u32]) {
-        offset += self.abs_offset;
-        assert!(
-            offset >= self.anchor_offset,
-            "offset arguments should be increasing."
-        );
-        let delta_to_block_offset = offset as i64 - self.block_offset as i64;
-        if delta_to_block_offset < 0 || delta_to_block_offset >= 128 {
-            // The first position is not within the first block.
-            // We need to decompress the first block.
-            let delta_to_anchor_offset = offset - self.anchor_offset;
-            let num_blocks_to_skip =
-                (delta_to_anchor_offset / (COMPRESSION_BLOCK_SIZE as u64)) as usize;
-            self.advance_num_blocks(num_blocks_to_skip);
-            self.anchor_offset = offset - (offset % COMPRESSION_BLOCK_SIZE as u64);
-            self.block_offset = self.anchor_offset;
-            let num_bits = self.skip_read.get(0);
-            self.bit_packer
-                .decompress(self.position_read.as_ref(), self.buffer.as_mut(), num_bits);
-        } else {
-            let num_blocks_to_skip =
-                ((self.block_offset - self.anchor_offset) / COMPRESSION_BLOCK_SIZE as u64) as usize;
-            self.advance_num_blocks(num_blocks_to_skip);
-            self.anchor_offset = self.block_offset;
-        }
-
-        let mut num_bits = self.skip_read.get(0);
-        let mut position_data = self.position_read.as_ref();
-
-        for i in 1.. {
-            let offset_in_block = (offset as usize) % COMPRESSION_BLOCK_SIZE;
-            let remaining_in_block = COMPRESSION_BLOCK_SIZE - offset_in_block;
-            if remaining_in_block >= output.len() {
-                output.copy_from_slice(&self.buffer[offset_in_block..][..output.len()]);
-                break;
-            }
-            output[..remaining_in_block].copy_from_slice(&self.buffer[offset_in_block..]);
-            output = &mut output[remaining_in_block..];
-            offset += remaining_in_block as u64;
-            position_data = &position_data[(num_bits as usize * COMPRESSION_BLOCK_SIZE / 8)..];
-            num_bits = self.skip_read.get(i);
+    /// Fills a buffer with the next `output.len()` integers.
+    /// This does not consume / advance the stream.
+    pub fn read(&mut self, output: &mut [u32]) {
+        let skip_data = self.skip_read.as_ref();
+        let position_data = self.position_read.as_ref();
+        let num_bits = self.skip_read.get(0);
+        if self.ahead != Some(0) {
+            // the block currently available is not the block
+            // for the current position
             self.bit_packer
                 .decompress(position_data, self.buffer.as_mut(), num_bits);
-            self.block_offset += COMPRESSION_BLOCK_SIZE as u64;
+            self.ahead = Some(0);
         }
+        let block_len = compressed_block_size(num_bits);
+        self.ahead = Some(read_impl(
+            self.bit_packer,
+            &position_data[block_len..],
+            self.buffer.as_mut(),
+            self.inner_offset,
+            &skip_data[1..],
+            output,
+        ));
+    }
+
+    /// Skip the next `skip_len` integer.
+    ///
+    /// If a full block is skipped, calling
+    /// `.skip(...)` will avoid decompressing it.
+    ///
+    /// May panic if the end of the stream is reached.
+    pub fn skip(&mut self, skip_len: usize) {
+        let skip_len_plus_inner_offset = skip_len + self.inner_offset;
+
+        let num_blocks_to_advance = skip_len_plus_inner_offset / COMPRESSION_BLOCK_SIZE;
+        self.inner_offset = skip_len_plus_inner_offset % COMPRESSION_BLOCK_SIZE;
+
+        self.ahead = self.ahead.and_then(|num_blocks| {
+            if num_blocks >= num_blocks_to_advance {
+                Some(num_blocks - num_blocks_to_advance)
+            } else {
+                None
+            }
+        });
+
+        let skip_len_in_bits = self.skip_read.as_ref()[..num_blocks_to_advance]
+            .iter()
+            .map(|num_bits| *num_bits as usize)
+            .sum::<usize>()
+            * COMPRESSION_BLOCK_SIZE;
+        let skip_len_in_bytes = skip_len_in_bits / 8;
+        self.skip_read.advance(num_blocks_to_advance);
+        self.position_read.advance(skip_len_in_bytes);
     }
 }

src/postings/block_search.rs

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

src/postings/block_segment_postings.rs

@@ -1,527 +0,0 @@
-use crate::common::{BinarySerializable, VInt};
-use crate::directory::ReadOnlySource;
-use crate::fieldnorm::FieldNormReader;
-use crate::postings::compression::{
-    AlignedBuffer, BlockDecoder, VIntDecoder, COMPRESSION_BLOCK_SIZE,
-};
-use crate::postings::{BlockInfo, FreqReadingOption, SkipReader};
-use crate::query::BM25Weight;
-use crate::schema::IndexRecordOption;
-use crate::{DocId, Score, TERMINATED};
-
-fn max_score<I: Iterator<Item = Score>>(mut it: I) -> Option<Score> {
-    if let Some(first) = it.next() {
-        Some(it.fold(first, Score::max))
-    } else {
-        None
-    }
-}
-
-/// `BlockSegmentPostings` is a cursor iterating over blocks
-/// of documents.
-///
-/// # Warning
-///
-/// While it is useful for some very specific high-performance
-/// use cases, you should prefer using `SegmentPostings` for most usage.
-#[derive(Clone)]
-pub struct BlockSegmentPostings {
-    pub(crate) doc_decoder: BlockDecoder,
-    loaded_offset: usize,
-    freq_decoder: BlockDecoder,
-    freq_reading_option: FreqReadingOption,
-    block_max_score_cache: Option<Score>,
-
-    doc_freq: u32,
-
-    data: ReadOnlySource,
-    pub(crate) skip_reader: SkipReader,
-}
-
-fn decode_bitpacked_block(
-    doc_decoder: &mut BlockDecoder,
-    freq_decoder_opt: Option<&mut BlockDecoder>,
-    data: &[u8],
-    doc_offset: DocId,
-    doc_num_bits: u8,
-    tf_num_bits: u8,
-) {
-    let num_consumed_bytes = doc_decoder.uncompress_block_sorted(data, doc_offset, doc_num_bits);
-    if let Some(freq_decoder) = freq_decoder_opt {
-        freq_decoder.uncompress_block_unsorted(&data[num_consumed_bytes..], tf_num_bits);
-    }
-}
-
-fn decode_vint_block(
-    doc_decoder: &mut BlockDecoder,
-    freq_decoder_opt: Option<&mut BlockDecoder>,
-    data: &[u8],
-    doc_offset: DocId,
-    num_vint_docs: usize,
-) {
-    let num_consumed_bytes =
-        doc_decoder.uncompress_vint_sorted(data, doc_offset, num_vint_docs, TERMINATED);
-    if let Some(freq_decoder) = freq_decoder_opt {
-        freq_decoder.uncompress_vint_unsorted(
-            &data[num_consumed_bytes..],
-            num_vint_docs,
-            TERMINATED,
-        );
-    }
-}
-
-fn split_into_skips_and_postings(
-    doc_freq: u32,
-    data: ReadOnlySource,
-) -> (Option<ReadOnlySource>, ReadOnlySource) {
-    if doc_freq < COMPRESSION_BLOCK_SIZE as u32 {
-        return (None, data);
-    }
-    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 from_data(
-        doc_freq: u32,
-        data: ReadOnlySource,
-        record_option: IndexRecordOption,
-        requested_option: IndexRecordOption,
-    ) -> 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);
-        let skip_reader = match skip_data_opt {
-            Some(skip_data) => SkipReader::new(skip_data, doc_freq, record_option),
-            None => SkipReader::new(ReadOnlySource::empty(), doc_freq, record_option),
-        };
-
-        let mut block_segment_postings = BlockSegmentPostings {
-            doc_decoder: BlockDecoder::with_val(TERMINATED),
-            loaded_offset: std::usize::MAX,
-            freq_decoder: BlockDecoder::with_val(1),
-            freq_reading_option,
-            block_max_score_cache: None,
-            doc_freq,
-            data: postings_data,
-            skip_reader,
-        };
-        block_segment_postings.load_block();
-        block_segment_postings
-    }
-
-    /// Returns the block_max_score for the current block.
-    /// It does not require the block to be loaded. For instance, it is ok to call this method
-    /// after having called `.shallow_advance(..)`.
-    ///
-    /// See `TermScorer::block_max_score(..)` for more information.
-    pub fn block_max_score(
-        &mut self,
-        fieldnorm_reader: &FieldNormReader,
-        bm25_weight: &BM25Weight,
-    ) -> Score {
-        if let Some(score) = self.block_max_score_cache {
-            return score;
-        }
-        if let Some(skip_reader_max_score) = self.skip_reader.block_max_score(bm25_weight) {
-            // if we are on a full block, the skip reader should have the block max information
-            // for us
-            self.block_max_score_cache = Some(skip_reader_max_score);
-            return skip_reader_max_score;
-        }
-        // this is the last block of the segment posting list.
-        // If it is actually loaded, we can compute block max manually.
-        if self.block_is_loaded() {
-            let docs = self.doc_decoder.output_array().iter().cloned();
-            let freqs = self.freq_decoder.output_array().iter().cloned();
-            let bm25_scores = docs.zip(freqs).map(|(doc, term_freq)| {
-                let fieldnorm_id = fieldnorm_reader.fieldnorm_id(doc);
-                bm25_weight.score(fieldnorm_id, term_freq)
-            });
-            let block_max_score = max_score(bm25_scores).unwrap_or(0.0);
-            self.block_max_score_cache = Some(block_max_score);
-            return block_max_score;
-        }
-        // We do not have access to any good block max value. We return bm25_weight.max_score()
-        // as it is a valid upperbound.
-        //
-        // We do not cache it however, so that it gets computed when once block is loaded.
-        bm25_weight.max_score()
-    }
-
-    pub(crate) fn freq_reading_option(&self) -> FreqReadingOption {
-        self.freq_reading_option
-    }
-
-    // Resets the block segment postings on another position
-    // in the postings file.
-    //
-    // This is useful for enumerating through a list of terms,
-    // and consuming the associated posting lists while avoiding
-    // reallocating a `BlockSegmentPostings`.
-    //
-    // # Warning
-    //
-    // This does not reset the positions list.
-    pub(crate) fn reset(&mut self, doc_freq: u32, postings_data: ReadOnlySource) {
-        let (skip_data_opt, postings_data) = split_into_skips_and_postings(doc_freq, 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(ReadOnlySource::empty(), doc_freq);
-        }
-        self.doc_freq = doc_freq;
-        self.load_block();
-    }
-
-    /// Returns the overall number of documents in the block postings.
-    /// It does not take in account whether documents are deleted or not.
-    ///
-    /// This `doc_freq` is simply the sum of the length of all of the blocks
-    /// length, and it does not take in account deleted documents.
-    pub fn doc_freq(&self) -> u32 {
-        self.doc_freq
-    }
-
-    /// Returns the array of docs in the current block.
-    ///
-    /// Before the first call to `.advance()`, the block
-    /// returned by `.docs()` is empty.
-    #[inline]
-    pub fn docs(&self) -> &[DocId] {
-        debug_assert!(self.block_is_loaded());
-        self.doc_decoder.output_array()
-    }
-
-    /// Returns a full block, regardless of whetehr the block is complete or incomplete (
-    /// as it happens for the last block of the posting list).
-    ///
-    /// In the latter case, the block is guaranteed to be padded with the sentinel value:
-    /// `TERMINATED`. The array is also guaranteed to be aligned on 16 bytes = 128 bits.
-    ///
-    /// This method is useful to run SSE2 linear search.
-    #[inline(always)]
-    pub(crate) fn docs_aligned(&self) -> &AlignedBuffer {
-        debug_assert!(self.block_is_loaded());
-        self.doc_decoder.output_aligned()
-    }
-
-    /// Return the document at index `idx` of the block.
-    #[inline(always)]
-    pub fn doc(&self, idx: usize) -> u32 {
-        self.doc_decoder.output(idx)
-    }
-
-    /// Return the array of `term freq` in the block.
-    #[inline]
-    pub fn freqs(&self) -> &[u32] {
-        debug_assert!(self.block_is_loaded());
-        self.freq_decoder.output_array()
-    }
-
-    /// Return the frequency at index `idx` of the block.
-    #[inline]
-    pub fn freq(&self, idx: usize) -> u32 {
-        debug_assert!(self.block_is_loaded());
-        self.freq_decoder.output(idx)
-    }
-
-    /// Returns the length of the current block.
-    ///
-    /// All blocks have a length of `NUM_DOCS_PER_BLOCK`,
-    /// except the last block that may have a length
-    /// of any number between 1 and `NUM_DOCS_PER_BLOCK - 1`
-    #[inline]
-    pub fn block_len(&self) -> usize {
-        debug_assert!(self.block_is_loaded());
-        self.doc_decoder.output_len
-    }
-
-    /// Position on a block that may contains `target_doc`.
-    ///
-    /// If all docs are smaller than target, the block loaded may be empty,
-    /// or be the last an incomplete VInt block.
-    pub fn seek(&mut self, target_doc: DocId) {
-        self.shallow_seek(target_doc);
-        self.load_block();
-    }
-
-    pub(crate) fn position_offset(&self) -> u64 {
-        self.skip_reader.position_offset()
-    }
-
-    /// Dangerous API! This calls seek on the skip list,
-    /// but does not `.load_block()` afterwards.
-    ///
-    /// `.load_block()` needs to be called manually afterwards.
-    /// If all docs are smaller than target, the block loaded may be empty,
-    /// or be the last an incomplete VInt block.
-    pub(crate) fn shallow_seek(&mut self, target_doc: DocId) {
-        if self.skip_reader.seek(target_doc) {
-            self.block_max_score_cache = None;
-        }
-    }
-
-    pub(crate) fn block_is_loaded(&self) -> bool {
-        self.loaded_offset == self.skip_reader.byte_offset()
-    }
-
-    pub(crate) fn load_block(&mut self) {
-        let offset = self.skip_reader.byte_offset();
-        if self.loaded_offset == offset {
-            return;
-        }
-        self.loaded_offset = offset;
-        match self.skip_reader.block_info() {
-            BlockInfo::BitPacked {
-                doc_num_bits,
-                tf_num_bits,
-                ..
-            } => {
-                decode_bitpacked_block(
-                    &mut self.doc_decoder,
-                    if let FreqReadingOption::ReadFreq = self.freq_reading_option {
-                        Some(&mut self.freq_decoder)
-                    } else {
-                        None
-                    },
-                    &self.data.as_slice()[offset..],
-                    self.skip_reader.last_doc_in_previous_block,
-                    doc_num_bits,
-                    tf_num_bits,
-                );
-            }
-            BlockInfo::VInt { num_docs } => {
-                let data = {
-                    if num_docs == 0 {
-                        &[]
-                    } else {
-                        &self.data.as_slice()[offset..]
-                    }
-                };
-                decode_vint_block(
-                    &mut self.doc_decoder,
-                    if let FreqReadingOption::ReadFreq = self.freq_reading_option {
-                        Some(&mut self.freq_decoder)
-                    } else {
-                        None
-                    },
-                    data,
-                    self.skip_reader.last_doc_in_previous_block,
-                    num_docs as usize,
-                );
-            }
-        }
-    }
-
-    /// Advance to the next block.
-    ///
-    /// Returns false iff there was no remaining blocks.
-    pub fn advance(&mut self) {
-        self.skip_reader.advance();
-        self.block_max_score_cache = None;
-        self.load_block();
-    }
-
-    /// Returns an empty segment postings object
-    pub fn empty() -> BlockSegmentPostings {
-        BlockSegmentPostings {
-            doc_decoder: BlockDecoder::with_val(TERMINATED),
-            loaded_offset: 0,
-            freq_decoder: BlockDecoder::with_val(1),
-            freq_reading_option: FreqReadingOption::NoFreq,
-            block_max_score_cache: None,
-            doc_freq: 0,
-            data: ReadOnlySource::new(vec![]),
-            skip_reader: SkipReader::new(ReadOnlySource::new(vec![]), 0, IndexRecordOption::Basic),
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::BlockSegmentPostings;
-    use crate::common::HasLen;
-    use crate::core::Index;
-    use crate::docset::{DocSet, TERMINATED};
-    use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
-    use crate::postings::postings::Postings;
-    use crate::postings::SegmentPostings;
-    use crate::schema::IndexRecordOption;
-    use crate::schema::Schema;
-    use crate::schema::Term;
-    use crate::schema::INDEXED;
-    use crate::DocId;
-
-    #[test]
-    fn test_empty_segment_postings() {
-        let mut postings = SegmentPostings::empty();
-        assert_eq!(postings.doc(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
-        assert_eq!(postings.doc_freq(), 0);
-        assert_eq!(postings.len(), 0);
-    }
-
-    #[test]
-    fn test_empty_postings_doc_returns_terminated() {
-        let mut postings = SegmentPostings::empty();
-        assert_eq!(postings.doc(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
-    }
-
-    #[test]
-    fn test_empty_postings_doc_term_freq_returns_0() {
-        let postings = SegmentPostings::empty();
-        assert_eq!(postings.term_freq(), 1);
-    }
-
-    #[test]
-    fn test_empty_block_segment_postings() {
-        let mut postings = BlockSegmentPostings::empty();
-        assert!(postings.docs().is_empty());
-        assert_eq!(postings.doc_freq(), 0);
-        postings.advance();
-        assert!(postings.docs().is_empty());
-        assert_eq!(postings.doc_freq(), 0);
-    }
-
-    #[test]
-    fn test_block_segment_postings() {
-        let mut block_segments = build_block_postings(&(0..100_000).collect::<Vec<u32>>());
-        let mut offset: u32 = 0u32;
-        // checking that the `doc_freq` is correct
-        assert_eq!(block_segments.doc_freq(), 100_000);
-        loop {
-            let block = block_segments.docs();
-            if block.is_empty() {
-                break;
-            }
-            for (i, doc) in block.iter().cloned().enumerate() {
-                assert_eq!(offset + (i as u32), doc);
-            }
-            offset += block.len() as u32;
-            block_segments.advance();
-        }
-    }
-
-    #[test]
-    fn test_skip_right_at_new_block() {
-        let mut doc_ids = (0..128).collect::<Vec<u32>>();
-        // 128 is missing
-        doc_ids.push(129);
-        doc_ids.push(130);
-        {
-            let block_segments = build_block_postings(&doc_ids);
-            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
-            assert_eq!(docset.seek(128), 129);
-            assert_eq!(docset.doc(), 129);
-            assert_eq!(docset.advance(), 130);
-            assert_eq!(docset.doc(), 130);
-            assert_eq!(docset.advance(), TERMINATED);
-        }
-        {
-            let block_segments = build_block_postings(&doc_ids);
-            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
-            assert_eq!(docset.seek(129), 129);
-            assert_eq!(docset.doc(), 129);
-            assert_eq!(docset.advance(), 130);
-            assert_eq!(docset.doc(), 130);
-            assert_eq!(docset.advance(), TERMINATED);
-        }
-        {
-            let block_segments = build_block_postings(&doc_ids);
-            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
-            assert_eq!(docset.doc(), 0);
-            assert_eq!(docset.seek(131), TERMINATED);
-            assert_eq!(docset.doc(), TERMINATED);
-        }
-    }
-
-    fn build_block_postings(docs: &[DocId]) -> BlockSegmentPostings {
-        let mut schema_builder = Schema::builder();
-        let int_field = schema_builder.add_u64_field("id", INDEXED);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
-        let mut last_doc = 0u32;
-        for &doc in docs {
-            for _ in last_doc..doc {
-                index_writer.add_document(doc!(int_field=>1u64));
-            }
-            index_writer.add_document(doc!(int_field=>0u64));
-            last_doc = doc + 1;
-        }
-        index_writer.commit().unwrap();
-        let searcher = index.reader().unwrap().searcher();
-        let segment_reader = searcher.segment_reader(0);
-        let inverted_index = segment_reader.inverted_index(int_field);
-        let term = Term::from_field_u64(int_field, 0u64);
-        let term_info = inverted_index.get_term_info(&term).unwrap();
-        inverted_index.read_block_postings_from_terminfo(&term_info, IndexRecordOption::Basic)
-    }
-
-    #[test]
-    fn test_block_segment_postings_seek() {
-        let mut docs = vec![0];
-        for i in 0..1300 {
-            docs.push((i * i / 100) + i);
-        }
-        let mut block_postings = build_block_postings(&docs[..]);
-        for i in vec![0, 424, 10000] {
-            block_postings.seek(i);
-            let docs = block_postings.docs();
-            assert!(docs[0] <= i);
-            assert!(docs.last().cloned().unwrap_or(0u32) >= i);
-        }
-        block_postings.seek(100_000);
-        assert_eq!(block_postings.doc(COMPRESSION_BLOCK_SIZE - 1), TERMINATED);
-    }
-
-    #[test]
-    fn test_reset_block_segment_postings() {
-        let mut schema_builder = Schema::builder();
-        let int_field = schema_builder.add_u64_field("id", INDEXED);
-        let schema = schema_builder.build();
-        let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests().unwrap();
-        // 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().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();
-            block_segments = inverted_index
-                .read_block_postings_from_terminfo(&term_info, IndexRecordOption::Basic);
-        }
-        assert_eq!(block_segments.docs(), &[0, 2, 4]);
-        {
-            let term = Term::from_field_u64(int_field, 1u64);
-            let inverted_index = segment_reader.inverted_index(int_field);
-            let term_info = inverted_index.get_term_info(&term).unwrap();
-            inverted_index.reset_block_postings_from_terminfo(&term_info, &mut block_segments);
-        }
-        assert_eq!(block_segments.docs(), &[1, 3, 5]);
-    }
-}

src/postings/compression/mod.rs

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

src/postings/compression/vint.rs

@@ -42,7 +42,7 @@ pub(crate) fn compress_unsorted<'a>(input: &[u32], output: &'a mut [u8]) -> &'a
 }
 
 #[inline(always)]
-pub fn uncompress_sorted(compressed_data: &[u8], output: &mut [u32], offset: u32) -> usize {
+pub fn uncompress_sorted<'a>(compressed_data: &'a [u8], output: &mut [u32], offset: u32) -> usize {
     let mut read_byte = 0;
     let mut result = offset;
     for output_mut in output.iter_mut() {

src/postings/mod.rs

@@ -3,8 +3,11 @@ Postings module (also called inverted index)
 */
 
 mod block_search;
-mod block_segment_postings;
 pub(crate) mod compression;
+/// Postings module
+///
+/// Postings, also called inverted lists, is the key datastructure
+/// to full-text search.
 mod postings;
 mod postings_writer;
 mod recorder;
@@ -19,17 +22,18 @@ pub(crate) use self::block_search::BlockSearcher;
 pub(crate) use self::postings_writer::MultiFieldPostingsWriter;
 pub use self::serializer::{FieldSerializer, InvertedIndexSerializer};
 
+use self::compression::COMPRESSION_BLOCK_SIZE;
 pub use self::postings::Postings;
-pub(crate) use self::skip::{BlockInfo, SkipReader};
+pub(crate) use self::skip::SkipReader;
 pub use self::term_info::TermInfo;
 
-pub use self::block_segment_postings::BlockSegmentPostings;
-pub use self::segment_postings::SegmentPostings;
+pub use self::segment_postings::{BlockSegmentPostings, SegmentPostings};
 
 pub(crate) use self::stacker::compute_table_size;
 
 pub use crate::common::HasLen;
 
+pub(crate) const USE_SKIP_INFO_LIMIT: u32 = COMPRESSION_BLOCK_SIZE as u32;
 pub(crate) type UnorderedTermId = u64;
 
 #[cfg_attr(feature = "cargo-clippy", allow(clippy::enum_variant_names))]
@@ -47,10 +51,10 @@ pub mod tests {
     use crate::core::Index;
     use crate::core::SegmentComponent;
     use crate::core::SegmentReader;
-    use crate::docset::{DocSet, TERMINATED};
+    use crate::docset::{DocSet, SkipResult};
     use crate::fieldnorm::FieldNormReader;
     use crate::indexer::operation::AddOperation;
-    use crate::indexer::SegmentWriter;
+    use crate::indexer::{IndexWriterConfig, SegmentWriter, ResourceManager};
     use crate::merge_policy::NoMergePolicy;
     use crate::query::Scorer;
     use crate::schema::{Document, Schema, Term, INDEXED, STRING, TEXT};
@@ -65,42 +69,45 @@ pub mod tests {
     use std::iter;
 
     #[test]
-    pub fn test_position_write() -> crate::Result<()> {
+    pub fn test_position_write() {
         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 segment = index.new_segment();
-        let mut posting_serializer = InvertedIndexSerializer::open(&mut segment)?;
-        let mut field_serializer = posting_serializer.new_field(text_field, 120 * 4, None)?;
-        field_serializer.new_term("abc".as_bytes(), 12u32)?;
-        for doc_id in 0u32..120u32 {
-            let delta_positions = vec![1, 2, 3, 2];
-            field_serializer.write_doc(doc_id, 4, &delta_positions)?;
+        let mut posting_serializer = InvertedIndexSerializer::open(&mut segment).unwrap();
+        {
+            let mut field_serializer = posting_serializer.new_field(text_field, 120 * 4).unwrap();
+            field_serializer.new_term("abc".as_bytes()).unwrap();
+            for doc_id in 0u32..120u32 {
+                let delta_positions = vec![1, 2, 3, 2];
+                field_serializer
+                    .write_doc(doc_id, 4, &delta_positions)
+                    .unwrap();
+            }
+            field_serializer.close_term().unwrap();
         }
-        field_serializer.close_term()?;
-        posting_serializer.close()?;
-        let read = segment.open_read(SegmentComponent::POSITIONS)?;
+        posting_serializer.close().unwrap();
+        let read = segment.open_read(SegmentComponent::POSITIONS).unwrap();
         assert!(read.len() <= 140);
-        Ok(())
     }
 
     #[test]
-    pub fn test_skip_positions() -> crate::Result<()> {
+    pub fn test_skip_positions() {
         let mut schema_builder = Schema::builder();
         let title = schema_builder.add_text_field("title", TEXT);
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
-        let mut index_writer = index.writer_for_tests()?;
+        let mut index_writer = index.writer_with_num_threads(1, 30_000_000).unwrap();
         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 {
             index_writer.add_document(doc!(title => r#"abc abc abc"#));
         }
         index_writer.add_document(doc!(title => r#"abc be be be be abc"#));
-        index_writer.commit()?;
+        index_writer.commit().unwrap();
 
-        let searcher = index.reader()?.searcher();
+        let searcher = index.reader().unwrap().searcher();
         let inverted_index = searcher.segment_reader(0u32).inverted_index(title);
         let term = Term::from_field_text(title, "abc");
         let mut positions = Vec::new();
@@ -108,12 +115,29 @@ pub mod tests {
             let mut postings = inverted_index
                 .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
-            assert_eq!(postings.doc(), 0);
+            postings.advance();
             postings.positions(&mut positions);
             assert_eq!(&[0, 1, 2], &positions[..]);
             postings.positions(&mut positions);
             assert_eq!(&[0, 1, 2], &positions[..]);
-            assert_eq!(postings.advance(), 1);
+            postings.advance();
+            postings.positions(&mut positions);
+            assert_eq!(&[0, 5], &positions[..]);
+        }
+        {
+            let mut postings = inverted_index
+                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
+                .unwrap();
+            postings.advance();
+            postings.advance();
+            postings.positions(&mut positions);
+            assert_eq!(&[0, 5], &positions[..]);
+        }
+        {
+            let mut postings = inverted_index
+                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
+                .unwrap();
+            assert_eq!(postings.skip_next(1), SkipResult::Reached);
             assert_eq!(postings.doc(), 1);
             postings.positions(&mut positions);
             assert_eq!(&[0, 5], &positions[..]);
@@ -122,25 +146,7 @@ pub mod tests {
             let mut postings = inverted_index
                 .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
-            assert_eq!(postings.doc(), 0);
-            assert_eq!(postings.advance(), 1);
-            postings.positions(&mut positions);
-            assert_eq!(&[0, 5], &positions[..]);
-        }
-        {
-            let mut postings = inverted_index
-                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
-                .unwrap();
-            assert_eq!(postings.seek(1), 1);
-            assert_eq!(postings.doc(), 1);
-            postings.positions(&mut positions);
-            assert_eq!(&[0, 5], &positions[..]);
-        }
-        {
-            let mut postings = inverted_index
-                .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
-                .unwrap();
-            assert_eq!(postings.seek(1002), 1002);
+            assert_eq!(postings.skip_next(1002), SkipResult::Reached);
             assert_eq!(postings.doc(), 1002);
             postings.positions(&mut positions);
             assert_eq!(&[0, 5], &positions[..]);
@@ -149,13 +155,12 @@ pub mod tests {
             let mut postings = inverted_index
                 .read_postings(&term, IndexRecordOption::WithFreqsAndPositions)
                 .unwrap();
-            assert_eq!(postings.seek(100), 100);
-            assert_eq!(postings.seek(1002), 1002);
+            assert_eq!(postings.skip_next(100), SkipResult::Reached);
+            assert_eq!(postings.skip_next(1002), SkipResult::Reached);
             assert_eq!(postings.doc(), 1002);
             postings.positions(&mut positions);
             assert_eq!(&[0, 5], &positions[..]);
         }
-        Ok(())
     }
 
     #[test]
@@ -176,7 +181,7 @@ 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));
@@ -205,50 +210,61 @@ pub mod tests {
     }
 
     #[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);
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema.clone());
-        let segment = index.new_segment();
 
-        {
-            let mut segment_writer =
-                SegmentWriter::for_segment(3_000_000, segment.clone(), &schema).unwrap();
+        let resource_manager = ResourceManager::default();
+        let segment = {
+            let mut segment_writer = SegmentWriter::for_segment(
+                &IndexWriterConfig::for_test(),
+                index.new_segment(),
+                &schema,
+                index.tokenizers(),
+                resource_manager
+            )
+            .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()?;
-        }
+            let (segment, _) = segment_writer.finalize().unwrap();
+            segment
+        };
         {
-            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 {
@@ -272,21 +288,22 @@ pub mod tests {
                     .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
                     .unwrap();
                 assert_eq!(postings_a.len(), 1000);
+                assert!(postings_a.advance());
                 assert_eq!(postings_a.doc(), 0);
                 assert_eq!(postings_a.term_freq(), 6);
                 postings_a.positions(&mut positions);
                 assert_eq!(&positions[..], [0, 2, 4, 6, 7, 13]);
-                assert_eq!(postings_a.advance(), 1u32);
+                assert!(postings_a.advance());
                 assert_eq!(postings_a.doc(), 1u32);
                 assert_eq!(postings_a.term_freq(), 1);
                 for i in 2u32..1000u32 {
-                    assert_eq!(postings_a.advance(), i);
+                    assert!(postings_a.advance());
                     assert_eq!(postings_a.term_freq(), 1);
                     postings_a.positions(&mut positions);
                     assert_eq!(&positions[..], [i]);
                     assert_eq!(postings_a.doc(), i);
                 }
-                assert_eq!(postings_a.advance(), TERMINATED);
+                assert!(!postings_a.advance());
             }
             {
                 let term_e = Term::from_field_text(text_field, "e");
@@ -296,6 +313,7 @@ pub mod tests {
                     .unwrap();
                 assert_eq!(postings_e.len(), 1000 - 2);
                 for i in 2u32..1000u32 {
+                    assert!(postings_e.advance());
                     assert_eq!(postings_e.term_freq(), i);
                     postings_e.positions(&mut positions);
                     assert_eq!(positions.len(), i as usize);
@@ -303,12 +321,10 @@ pub mod tests {
                         assert_eq!(positions[j], (j as u32));
                     }
                     assert_eq!(postings_e.doc(), i);
-                    postings_e.advance();
                 }
-                assert_eq!(postings_e.doc(), TERMINATED);
+                assert!(!postings_e.advance());
             }
         }
-        Ok(())
     }
 
     #[test]
@@ -319,9 +335,17 @@ pub mod tests {
         let schema = schema_builder.build();
         let index = Index::create_in_ram(schema);
         {
-            let mut index_writer = index.writer_for_tests().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"));
+            let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+            {
+                let mut doc = Document::default();
+                doc.add_text(text_field, "g b b d c g c");
+                index_writer.add_document(doc);
+            }
+            {
+                let mut doc = Document::default();
+                doc.add_text(text_field, "g a b b a d c g c");
+                index_writer.add_document(doc);
+            }
             assert!(index_writer.commit().is_ok());
         }
         let term_a = Term::from_field_text(text_field, "a");
@@ -331,6 +355,7 @@ pub mod tests {
             .inverted_index(text_field)
             .read_postings(&term_a, IndexRecordOption::WithFreqsAndPositions)
             .unwrap();
+        assert!(postings.advance());
         assert_eq!(postings.doc(), 1u32);
         postings.positions(&mut positions);
         assert_eq!(&positions[..], &[1u32, 4]);
@@ -351,9 +376,12 @@ pub mod tests {
 
             let index = Index::create_in_ram(schema);
             {
-                let mut index_writer = index.writer_for_tests().unwrap();
-                for i in 0u64..num_docs as u64 {
-                    let doc = doc!(value_field => 2u64, value_field => i % 2u64);
+                let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+                for i in 0..num_docs {
+                    let mut doc = Document::default();
+                    doc.add_u64(value_field, 2);
+                    doc.add_u64(value_field, (i % 2) as u64);
+
                     index_writer.add_document(doc);
                 }
                 assert!(index_writer.commit().is_ok());
@@ -370,10 +398,11 @@ pub mod tests {
                     .inverted_index(term_2.field())
                     .read_postings(&term_2, IndexRecordOption::Basic)
                     .unwrap();
-                assert_eq!(segment_postings.seek(i), i);
+
+                assert_eq!(segment_postings.skip_next(i), SkipResult::Reached);
                 assert_eq!(segment_postings.doc(), i);
 
-                assert_eq!(segment_postings.seek(j), j);
+                assert_eq!(segment_postings.skip_next(j), SkipResult::Reached);
                 assert_eq!(segment_postings.doc(), j);
             }
         }
@@ -385,16 +414,17 @@ pub mod tests {
                 .unwrap();
 
             // check that `skip_next` advances the iterator
+            assert!(segment_postings.advance());
             assert_eq!(segment_postings.doc(), 0);
 
-            assert_eq!(segment_postings.seek(1), 1);
+            assert_eq!(segment_postings.skip_next(1), SkipResult::Reached);
             assert_eq!(segment_postings.doc(), 1);
 
-            assert_eq!(segment_postings.seek(1), 1);
-            assert_eq!(segment_postings.doc(), 1);
+            assert_eq!(segment_postings.skip_next(1), SkipResult::OverStep);
+            assert_eq!(segment_postings.doc(), 2);
 
             // check that going beyond the end is handled
-            assert_eq!(segment_postings.seek(num_docs), TERMINATED);
+            assert_eq!(segment_postings.skip_next(num_docs), SkipResult::End);
         }
 
         // check that filtering works
@@ -405,7 +435,7 @@ pub mod tests {
                 .unwrap();
 
             for i in 0..num_docs / 2 {
-                assert_eq!(segment_postings.seek(i * 2), i * 2);
+                assert_eq!(segment_postings.skip_next(i * 2), SkipResult::Reached);
                 assert_eq!(segment_postings.doc(), i * 2);
             }
 
@@ -415,19 +445,18 @@ pub mod tests {
                 .unwrap();
 
             for i in 0..num_docs / 2 - 1 {
-                assert!(segment_postings.seek(i * 2 + 1) > (i * 1) * 2);
+                assert_eq!(segment_postings.skip_next(i * 2 + 1), SkipResult::OverStep);
                 assert_eq!(segment_postings.doc(), (i + 1) * 2);
             }
         }
 
         // delete some of the documents
         {
-            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.delete_term(term_0);
             assert!(index_writer.commit().is_ok());
         }
         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
@@ -438,11 +467,11 @@ pub mod tests {
                 .unwrap();
 
             if i % 2 == 0 {
-                assert_eq!(segment_postings.seek(i), i);
+                assert_eq!(segment_postings.skip_next(i), SkipResult::Reached);
                 assert_eq!(segment_postings.doc(), i);
                 assert!(segment_reader.is_deleted(i));
             } else {
-                assert_eq!(segment_postings.seek(i), i);
+                assert_eq!(segment_postings.skip_next(i), SkipResult::Reached);
                 assert_eq!(segment_postings.doc(), i);
             }
         }
@@ -457,16 +486,12 @@ pub mod tests {
             let mut last = 2; // start from 5 to avoid seeking to 3 twice
             let mut cur = 3;
             loop {
-                let seek = segment_postings.seek(cur);
-                if seek == TERMINATED {
-                    break;
-                }
-                assert_eq!(seek, segment_postings.doc());
-                if seek == cur {
-                    assert_eq!(segment_postings.doc(), cur);
-                } else {
-                    assert_eq!(segment_postings.doc(), cur + 1);
+                match segment_postings.skip_next(cur) {
+                    SkipResult::End => break,
+                    SkipResult::Reached => assert_eq!(segment_postings.doc(), cur),
+                    SkipResult::OverStep => assert_eq!(segment_postings.doc(), cur + 1),
                 }
+
                 let next = cur + last;
                 last = cur;
                 cur = next;
@@ -476,7 +501,7 @@ pub mod tests {
 
         // delete everything else
         {
-            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.delete_term(term_1);
             assert!(index_writer.commit().is_ok());
         }
@@ -519,7 +544,7 @@ pub mod tests {
         let index = Index::create_in_ram(schema);
         let posting_list_size = 1_000_000;
         {
-            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..posting_list_size {
                 let mut doc = Document::default();
                 if rng.gen_bool(1f64 / 15f64) {
@@ -552,7 +577,7 @@ pub mod tests {
     }
 
     impl<TDocSet: DocSet> DocSet for UnoptimizedDocSet<TDocSet> {
-        fn advance(&mut self) -> DocId {
+        fn advance(&mut self) -> bool {
             self.0.advance()
         }
 
@@ -577,26 +602,31 @@ pub mod tests {
     ) {
         for target in targets {
             let mut postings_opt = postings_factory();
-            if target < postings_opt.doc() {
-                continue;
-            }
             let mut postings_unopt = UnoptimizedDocSet::wrap(postings_factory());
-            let skip_result_opt = postings_opt.seek(target);
-            let skip_result_unopt = postings_unopt.seek(target);
+            let skip_result_opt = postings_opt.skip_next(target);
+            let skip_result_unopt = postings_unopt.skip_next(target);
             assert_eq!(
                 skip_result_unopt, skip_result_opt,
                 "Failed while skipping to {}",
                 target
             );
-            assert!(skip_result_opt >= target);
-            assert_eq!(skip_result_opt, postings_opt.doc());
-            if skip_result_opt == TERMINATED {
-                return;
+            match skip_result_opt {
+                SkipResult::Reached => assert_eq!(postings_opt.doc(), target),
+                SkipResult::OverStep => assert!(postings_opt.doc() > target),
+                SkipResult::End => {
+                    return;
+                }
             }
-            while postings_opt.doc() != TERMINATED {
-                assert_eq!(postings_opt.doc(), postings_unopt.doc());
-                assert_eq!(postings_opt.advance(), postings_unopt.advance());
+            while postings_opt.advance() {
+                assert!(postings_unopt.advance());
+                assert_eq!(
+                    postings_opt.doc(),
+                    postings_unopt.doc(),
+                    "Failed while skipping to {}",
+                    target
+                );
             }
+            assert!(!postings_unopt.advance());
         }
     }
 }
@@ -605,7 +635,7 @@ pub mod tests {
 mod bench {
 
     use super::tests::*;
-    use crate::docset::TERMINATED;
+    use crate::docset::SkipResult;
     use crate::query::Intersection;
     use crate::schema::IndexRecordOption;
     use crate::tests;
@@ -623,7 +653,7 @@ mod bench {
                 .inverted_index(TERM_A.field())
                 .read_postings(&*TERM_A, IndexRecordOption::Basic)
                 .unwrap();
-            while segment_postings.advance() != TERMINATED {}
+            while segment_postings.advance() {}
         });
     }
 
@@ -655,7 +685,7 @@ mod bench {
                 segment_postings_c,
                 segment_postings_d,
             ]);
-            while intersection.advance() != TERMINATED {}
+            while intersection.advance() {}
         });
     }
 
@@ -671,10 +701,11 @@ mod bench {
             .unwrap();
 
         let mut existing_docs = Vec::new();
+        segment_postings.advance();
         for doc in &docs {
             if *doc >= segment_postings.doc() {
                 existing_docs.push(*doc);
-                if segment_postings.seek(*doc) == TERMINATED {
+                if segment_postings.skip_next(*doc) == SkipResult::End {
                     break;
                 }
             }
@@ -686,7 +717,7 @@ mod bench {
                 .read_postings(&*TERM_A, IndexRecordOption::Basic)
                 .unwrap();
             for doc in &existing_docs {
-                if segment_postings.seek(*doc) == TERMINATED {
+                if segment_postings.skip_next(*doc) == SkipResult::End {
                     break;
                 }
             }
@@ -725,9 +756,8 @@ mod bench {
                 .read_postings(&*TERM_A, IndexRecordOption::Basic)
                 .unwrap();
             let mut s = 0u32;
-            while segment_postings.doc() != TERMINATED {
+            while segment_postings.advance() {
                 s += (segment_postings.doc() & n) % 1024;
-                segment_postings.advance();
             }
             s
         });

src/postings/postings_writer.rs

@@ -1,6 +1,5 @@
 use super::stacker::{Addr, MemoryArena, TermHashMap};
 
-use crate::fieldnorm::FieldNormReaders;
 use crate::postings::recorder::{
     BufferLender, NothingRecorder, Recorder, TFAndPositionRecorder, TermFrequencyRecorder,
 };
@@ -96,7 +95,7 @@ impl MultiFieldPostingsWriter {
         }
     }
 
-    pub fn mem_usage(&self) -> usize {
+    pub fn mem_usage(&self) -> u64 {
         self.term_index.mem_usage() + self.heap.mem_usage()
     }
 
@@ -105,7 +104,6 @@ impl MultiFieldPostingsWriter {
         doc: DocId,
         field: Field,
         token_stream: &mut dyn TokenStream,
-        term_buffer: &mut Term,
     ) -> u32 {
         let postings_writer =
             self.per_field_postings_writers[field.field_id() as usize].deref_mut();
@@ -115,7 +113,6 @@ impl MultiFieldPostingsWriter {
             field,
             token_stream,
             &mut self.heap,
-            term_buffer,
         )
     }
 
@@ -131,7 +128,6 @@ impl MultiFieldPostingsWriter {
     pub fn serialize(
         &self,
         serializer: &mut InvertedIndexSerializer,
-        fieldnorm_readers: FieldNormReaders,
     ) -> crate::Result<HashMap<Field, FnvHashMap<UnorderedTermId, TermOrdinal>>> {
         let mut term_offsets: Vec<(&[u8], Addr, UnorderedTermId)> =
             self.term_index.iter().collect();
@@ -165,12 +161,8 @@ impl MultiFieldPostingsWriter {
             }
 
             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(),
-                fieldnorm_reader,
-            )?;
+            let mut field_serializer =
+                serializer.new_field(field, postings_writer.total_num_tokens())?;
             postings_writer.serialize(
                 &term_offsets[start..stop],
                 &mut field_serializer,
@@ -222,22 +214,21 @@ pub trait PostingsWriter {
         field: Field,
         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 {
-                return;
+            if token.text.len() <= MAX_TOKEN_LEN {
+                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 \
+                     MAX_TOKEN_LEN in the documentation for more information.",
+                    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,
-            );
         };
         token_stream.process(&mut sink)
     }
@@ -306,8 +297,7 @@ impl<Rec: Recorder + 'static> PostingsWriter for SpecializedPostingsWriter<Rec>
         let mut buffer_lender = BufferLender::default();
         for &(term_bytes, addr, _) in term_addrs {
             let recorder: Rec = termdict_heap.read(addr);
-            let term_doc_freq = recorder.term_doc_freq().unwrap_or(0u32);
-            serializer.new_term(&term_bytes[4..], term_doc_freq)?;
+            serializer.new_term(&term_bytes[4..])?;
             recorder.serialize(&mut buffer_lender, serializer, heap)?;
             serializer.close_term()?;
         }

src/postings/recorder.rs

@@ -75,10 +75,6 @@ pub(crate) trait Recorder: Copy + 'static {
         serializer: &mut FieldSerializer<'_>,
         heap: &MemoryArena,
     ) -> io::Result<()>;
-    /// Returns the number of document containing this term.
-    ///
-    /// Returns `None` if not available.
-    fn term_doc_freq(&self) -> Option<u32>;
 }
 
 /// Only records the doc ids
@@ -117,16 +113,11 @@ impl Recorder for NothingRecorder {
     ) -> io::Result<()> {
         let buffer = buffer_lender.lend_u8();
         self.stack.read_to_end(heap, buffer);
-        // TODO avoid reading twice.
         for doc in VInt32Reader::new(&buffer[..]) {
             serializer.write_doc(doc as u32, 0u32, &[][..])?;
         }
         Ok(())
     }
-
-    fn term_doc_freq(&self) -> Option<u32> {
-        None
-    }
 }
 
 /// Recorder encoding document ids, and term frequencies
@@ -135,7 +126,6 @@ pub struct TermFrequencyRecorder {
     stack: ExpUnrolledLinkedList,
     current_doc: DocId,
     current_tf: u32,
-    term_doc_freq: u32,
 }
 
 impl Recorder for TermFrequencyRecorder {
@@ -144,7 +134,6 @@ impl Recorder for TermFrequencyRecorder {
             stack: ExpUnrolledLinkedList::new(),
             current_doc: u32::max_value(),
             current_tf: 0u32,
-            term_doc_freq: 0u32,
         }
     }
 
@@ -153,7 +142,6 @@ impl Recorder for TermFrequencyRecorder {
     }
 
     fn new_doc(&mut self, doc: DocId, heap: &mut MemoryArena) {
-        self.term_doc_freq += 1;
         self.current_doc = doc;
         let _ = write_u32_vint(doc, &mut self.stack.writer(heap));
     }
@@ -184,10 +172,6 @@ impl Recorder for TermFrequencyRecorder {
 
         Ok(())
     }
-
-    fn term_doc_freq(&self) -> Option<u32> {
-        Some(self.term_doc_freq)
-    }
 }
 
 /// Recorder encoding term frequencies as well as positions.
@@ -195,14 +179,12 @@ impl Recorder for TermFrequencyRecorder {
 pub struct TFAndPositionRecorder {
     stack: ExpUnrolledLinkedList,
     current_doc: DocId,
-    term_doc_freq: u32,
 }
 impl Recorder for TFAndPositionRecorder {
     fn new() -> Self {
         TFAndPositionRecorder {
             stack: ExpUnrolledLinkedList::new(),
             current_doc: u32::max_value(),
-            term_doc_freq: 0u32,
         }
     }
 
@@ -212,7 +194,6 @@ impl Recorder for TFAndPositionRecorder {
 
     fn new_doc(&mut self, doc: DocId, heap: &mut MemoryArena) {
         self.current_doc = doc;
-        self.term_doc_freq += 1u32;
         let _ = write_u32_vint(doc, &mut self.stack.writer(heap));
     }
 
@@ -252,10 +233,6 @@ impl Recorder for TFAndPositionRecorder {
         }
         Ok(())
     }
-
-    fn term_doc_freq(&self) -> Option<u32> {
-        Some(self.term_doc_freq)
-    }
 }
 
 #[cfg(test)]

src/postings/segment_postings.rs

@@ -1,70 +1,81 @@
+use crate::common::BitSet;
 use crate::common::HasLen;
-
-use crate::docset::DocSet;
+use crate::common::{BinarySerializable, VInt};
+use crate::docset::{DocSet, SkipResult};
 use crate::positions::PositionReader;
-
-use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
+use crate::postings::compression::{compressed_block_size, AlignedBuffer};
+use crate::postings::compression::{BlockDecoder, VIntDecoder, COMPRESSION_BLOCK_SIZE};
 use crate::postings::serializer::PostingsSerializer;
 use crate::postings::BlockSearcher;
-
+use crate::postings::FreqReadingOption;
 use crate::postings::Postings;
-
+use crate::postings::SkipReader;
+use crate::postings::USE_SKIP_INFO_LIMIT;
 use crate::schema::IndexRecordOption;
-use crate::{DocId, TERMINATED};
+use crate::DocId;
+use owned_read::OwnedRead;
+use std::cmp::Ordering;
+use tantivy_fst::Streamer;
 
-use crate::directory::ReadOnlySource;
-use crate::fastfield::DeleteBitSet;
-use crate::postings::BlockSegmentPostings;
+struct PositionComputer {
+    // store the amount of position int
+    // before reading positions.
+    //
+    // if none, position are already loaded in
+    // the positions vec.
+    position_to_skip: usize,
+    position_reader: PositionReader,
+}
+
+impl PositionComputer {
+    pub fn new(position_reader: PositionReader) -> PositionComputer {
+        PositionComputer {
+            position_to_skip: 0,
+            position_reader,
+        }
+    }
+
+    pub fn add_skip(&mut self, num_skip: usize) {
+        self.position_to_skip += num_skip;
+    }
+
+    // Positions can only be read once.
+    pub fn positions_with_offset(&mut self, offset: u32, output: &mut [u32]) {
+        self.position_reader.skip(self.position_to_skip);
+        self.position_to_skip = 0;
+        self.position_reader.read(output);
+        let mut cum = offset;
+        for output_mut in output.iter_mut() {
+            cum += *output_mut;
+            *output_mut = cum;
+        }
+    }
+}
 
 /// `SegmentPostings` represents the inverted list or postings associated to
 /// a term in a `Segment`.
 ///
 /// As we iterate through the `SegmentPostings`, the frequencies are optionally decoded.
 /// Positions on the other hand, are optionally entirely decoded upfront.
-#[derive(Clone)]
 pub struct SegmentPostings {
-    pub(crate) block_cursor: BlockSegmentPostings,
+    block_cursor: BlockSegmentPostings,
     cur: usize,
-    position_reader: Option<PositionReader>,
+    position_computer: Option<PositionComputer>,
     block_searcher: BlockSearcher,
 }
 
 impl SegmentPostings {
     /// Returns an empty segment postings object
     pub fn empty() -> Self {
+        let empty_block_cursor = BlockSegmentPostings::empty();
         SegmentPostings {
-            block_cursor: BlockSegmentPostings::empty(),
-            cur: 0,
-            position_reader: None,
+            block_cursor: empty_block_cursor,
+            cur: COMPRESSION_BLOCK_SIZE,
+            position_computer: None,
             block_searcher: BlockSearcher::default(),
         }
     }
 
-    /// Compute the number of non-deleted documents.
-    ///
-    /// This method will clone and scan through the posting lists.
-    /// (this is a rather expensive operation).
-    pub fn doc_freq_given_deletes(&self, delete_bitset: &DeleteBitSet) -> u32 {
-        let mut docset = self.clone();
-        let mut doc_freq = 0;
-        loop {
-            let doc = docset.doc();
-            if doc == TERMINATED {
-                return doc_freq;
-            }
-            if delete_bitset.is_alive(doc) {
-                doc_freq += 1u32;
-            }
-            docset.advance();
-        }
-    }
-
-    /// Returns the overall number of documents in the block postings.
-    /// It does not take in account whether documents are deleted or not.
-    pub fn doc_freq(&self) -> u32 {
-        self.block_cursor.doc_freq()
-    }
-
     /// Creates a segment postings object with the given documents
     /// and no frequency encoded.
     ///
@@ -76,9 +87,7 @@ impl SegmentPostings {
     pub fn create_from_docs(docs: &[u32]) -> SegmentPostings {
         let mut buffer = Vec::new();
         {
-            let mut postings_serializer =
-                PostingsSerializer::new(&mut buffer, 0.0, false, false, None);
-            postings_serializer.new_term(docs.len() as u32);
+            let mut postings_serializer = PostingsSerializer::new(&mut buffer, false, false);
             for &doc in docs {
                 postings_serializer.write_doc(doc, 1u32);
             }
@@ -88,58 +97,15 @@ impl SegmentPostings {
         }
         let block_segment_postings = BlockSegmentPostings::from_data(
             docs.len() as u32,
-            ReadOnlySource::from(buffer),
+            OwnedRead::new(buffer),
             IndexRecordOption::Basic,
             IndexRecordOption::Basic,
         );
         SegmentPostings::from_block_postings(block_segment_postings, None)
     }
+}
 
-    /// Helper functions to create `SegmentPostings` for tests.
-    #[cfg(test)]
-    pub fn create_from_docs_and_tfs(
-        doc_and_tfs: &[(u32, u32)],
-        fieldnorms: Option<&[u32]>,
-    ) -> SegmentPostings {
-        use crate::fieldnorm::FieldNormReader;
-        use crate::Score;
-        let mut buffer: Vec<u8> = Vec::new();
-        let fieldnorm_reader = fieldnorms.map(FieldNormReader::for_test);
-        let average_field_norm = fieldnorms
-            .map(|fieldnorms| {
-                if fieldnorms.len() == 0 {
-                    return 0.0;
-                }
-                let total_num_tokens: u64 = fieldnorms
-                    .iter()
-                    .map(|&fieldnorm| fieldnorm as u64)
-                    .sum::<u64>();
-                total_num_tokens as Score / fieldnorms.len() as Score
-            })
-            .unwrap_or(0.0);
-        let mut postings_serializer = PostingsSerializer::new(
-            &mut buffer,
-            average_field_norm,
-            true,
-            false,
-            fieldnorm_reader,
-        );
-        postings_serializer.new_term(doc_and_tfs.len() as u32);
-        for &(doc, tf) in doc_and_tfs {
-            postings_serializer.write_doc(doc, tf);
-        }
-        postings_serializer
-            .close_term(doc_and_tfs.len() as u32)
-            .unwrap();
-        let block_segment_postings = BlockSegmentPostings::from_data(
-            doc_and_tfs.len() as u32,
-            ReadOnlySource::from(buffer),
-            IndexRecordOption::WithFreqs,
-            IndexRecordOption::WithFreqs,
-        );
-        SegmentPostings::from_block_postings(block_segment_postings, None)
-    }
-
+impl SegmentPostings {
     /// Reads a Segment postings from an &[u8]
     ///
     /// * `len` - number of document in the posting lists.
@@ -148,12 +114,12 @@ impl SegmentPostings {
     ///   frequencies and/or positions
     pub(crate) fn from_block_postings(
         segment_block_postings: BlockSegmentPostings,
-        position_reader: Option<PositionReader>,
+        positions_stream_opt: Option<PositionReader>,
     ) -> SegmentPostings {
         SegmentPostings {
             block_cursor: segment_block_postings,
-            cur: 0, // cursor within the block
-            position_reader,
+            cur: COMPRESSION_BLOCK_SIZE, // cursor within the block
+            position_computer: positions_stream_opt.map(PositionComputer::new),
             block_searcher: BlockSearcher::default(),
         }
     }
@@ -163,60 +129,139 @@ impl DocSet for SegmentPostings {
     // goes to the next element.
     // next needs to be called a first time to point to the correct element.
     #[inline]
-    fn advance(&mut self) -> DocId {
-        debug_assert!(self.block_cursor.block_is_loaded());
-        if self.cur == COMPRESSION_BLOCK_SIZE - 1 {
-            self.cur = 0;
-            self.block_cursor.advance();
-        } else {
-            self.cur += 1;
+    fn advance(&mut self) -> bool {
+        if self.position_computer.is_some() && self.cur < COMPRESSION_BLOCK_SIZE {
+            let term_freq = self.term_freq() as usize;
+            if let Some(position_computer) = self.position_computer.as_mut() {
+                position_computer.add_skip(term_freq);
+            }
         }
-        self.doc()
+        self.cur += 1;
+        if self.cur >= self.block_cursor.block_len() {
+            self.cur = 0;
+            if !self.block_cursor.advance() {
+                self.cur = COMPRESSION_BLOCK_SIZE;
+                return false;
+            }
+        }
+        true
     }
 
-    fn seek(&mut self, target: DocId) -> DocId {
-        debug_assert!(self.doc() <= target);
-        if self.doc() >= target {
-            return self.doc();
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
+        if !self.advance() {
+            return SkipResult::End;
+        }
+        match self.doc().cmp(&target) {
+            Ordering::Equal => {
+                return SkipResult::Reached;
+            }
+            Ordering::Greater => {
+                return SkipResult::OverStep;
+            }
+            _ => {
+                // ...
+            }
         }
 
-        self.block_cursor.seek(target);
+        // In the following, thanks to the call to advance above,
+        // we know that the position is not loaded and we need
+        // to skip every doc_freq we cross.
 
-        // At this point we are on the block, that might contain our document.
-        let output = self.block_cursor.docs_aligned();
-        self.cur = self.block_searcher.search_in_block(&output, target);
+        // skip blocks until one that might contain the target
+        // check if we need to go to the next block
+        let mut sum_freqs_skipped: u32 = 0;
+        if !self
+            .block_cursor
+            .docs()
+            .last()
+            .map(|doc| *doc >= target)
+            .unwrap_or(false)
+        // there should always be at least a document in the block
+        // since advance returned.
+        {
+            // we are not in the right block.
+            //
+            // First compute all of the freqs skipped from the current block.
+            if self.position_computer.is_some() {
+                sum_freqs_skipped = self.block_cursor.freqs()[self.cur..].iter().sum();
+                match self.block_cursor.skip_to(target) {
+                    BlockSegmentPostingsSkipResult::Success(block_skip_freqs) => {
+                        sum_freqs_skipped += block_skip_freqs;
+                    }
+                    BlockSegmentPostingsSkipResult::Terminated => {
+                        return SkipResult::End;
+                    }
+                }
+            } else if self.block_cursor.skip_to(target)
+                == BlockSegmentPostingsSkipResult::Terminated
+            {
+                // no positions needed. no need to sum freqs.
+                return SkipResult::End;
+            }
+            self.cur = 0;
+        }
 
-        // The last block is not full and padded with the value TERMINATED,
-        // so that we are guaranteed to have at least doc in the block (a real one or the padding)
-        // that is greater or equal to the target.
-        debug_assert!(self.cur < COMPRESSION_BLOCK_SIZE);
+        let cur = self.cur;
+
+        // we're in the right block now, start with an exponential search
+        let (output, len) = self.block_cursor.docs_aligned();
+        let new_cur = self
+            .block_searcher
+            .search_in_block(&output, len, cur, target);
+        if let Some(position_computer) = self.position_computer.as_mut() {
+            sum_freqs_skipped += self.block_cursor.freqs()[cur..new_cur].iter().sum::<u32>();
+            position_computer.add_skip(sum_freqs_skipped as usize);
+        }
+        self.cur = new_cur;
 
         // `doc` is now the first element >= `target`
-
-        // If all docs are smaller than target the current block should be incomplemented and padded
-        // with the value `TERMINATED`.
-        //
-        // After the search, the cursor should point to the first value of TERMINATED.
-        let doc = output.0[self.cur];
+        let doc = output.0[new_cur];
         debug_assert!(doc >= target);
-        debug_assert_eq!(doc, self.doc());
-        doc
+        if doc == target {
+            SkipResult::Reached
+        } else {
+            SkipResult::OverStep
+        }
     }
 
     /// Return the current document's `DocId`.
+    ///
+    /// # Panics
+    ///
+    /// Will panics if called without having called advance before.
     #[inline]
     fn doc(&self) -> DocId {
-        self.block_cursor.doc(self.cur)
+        let docs = self.block_cursor.docs();
+        debug_assert!(
+            self.cur < docs.len(),
+            "Have you forgotten to call `.advance()` at least once before calling `.doc()`                                      ."
+        );
+        docs[self.cur]
     }
 
     fn size_hint(&self) -> u32 {
         self.len() as u32
     }
+
+    fn append_to_bitset(&mut self, bitset: &mut BitSet) {
+        // finish the current block
+        if self.advance() {
+            for &doc in &self.block_cursor.docs()[self.cur..] {
+                bitset.insert(doc);
+            }
+            // ... iterate through the remaining blocks.
+            while self.block_cursor.advance() {
+                for &doc in self.block_cursor.docs() {
+                    bitset.insert(doc);
+                }
+            }
+        }
+    }
 }
 
 impl HasLen for SegmentPostings {
     fn len(&self) -> usize {
-        self.block_cursor.doc_freq() as usize
+        self.block_cursor.doc_freq()
     }
 }
 
@@ -245,63 +290,515 @@ impl Postings for SegmentPostings {
 
     fn positions_with_offset(&mut self, offset: u32, output: &mut Vec<u32>) {
         let term_freq = self.term_freq() as usize;
-        if let Some(position_reader) = self.position_reader.as_mut() {
-            let read_offset = self.block_cursor.position_offset()
-                + (self.block_cursor.freqs()[..self.cur]
-                    .iter()
-                    .cloned()
-                    .sum::<u32>() as u64);
+        if let Some(position_comp) = self.position_computer.as_mut() {
             output.resize(term_freq, 0u32);
-            position_reader.read(read_offset, &mut output[..]);
-            let mut cum = offset;
-            for output_mut in output.iter_mut() {
-                cum += *output_mut;
-                *output_mut = cum;
-            }
+            position_comp.positions_with_offset(offset, &mut output[..]);
         } else {
             output.clear();
         }
     }
 }
 
+/// `BlockSegmentPostings` is a cursor iterating over blocks
+/// of documents.
+///
+/// # Warning
+///
+/// While it is useful for some very specific high-performance
+/// use cases, you should prefer using `SegmentPostings` for most usage.
+pub struct BlockSegmentPostings {
+    doc_decoder: BlockDecoder,
+    freq_decoder: BlockDecoder,
+    freq_reading_option: FreqReadingOption,
+
+    doc_freq: usize,
+    doc_offset: DocId,
+
+    num_vint_docs: usize,
+
+    remaining_data: OwnedRead,
+    skip_reader: SkipReader,
+}
+
+fn split_into_skips_and_postings(
+    doc_freq: u32,
+    mut data: OwnedRead,
+) -> (Option<OwnedRead>, OwnedRead) {
+    if doc_freq >= USE_SKIP_INFO_LIMIT {
+        let skip_len = VInt::deserialize(&mut data).expect("Data corrupted").0 as usize;
+        let mut postings_data = data.clone();
+        postings_data.advance(skip_len);
+        data.clip(skip_len);
+        (Some(data), postings_data)
+    } else {
+        (None, data)
+    }
+}
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum BlockSegmentPostingsSkipResult {
+    Terminated,
+    Success(u32), //< number of term freqs to skip
+}
+
+impl BlockSegmentPostings {
+    pub(crate) fn from_data(
+        doc_freq: u32,
+        data: OwnedRead,
+        record_option: IndexRecordOption,
+        requested_option: IndexRecordOption,
+    ) -> 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);
+        let skip_reader = match skip_data_opt {
+            Some(skip_data) => SkipReader::new(skip_data, record_option),
+            None => SkipReader::new(OwnedRead::new(&[][..]), record_option),
+        };
+        let doc_freq = doc_freq as usize;
+        let num_vint_docs = doc_freq % COMPRESSION_BLOCK_SIZE;
+        BlockSegmentPostings {
+            num_vint_docs,
+            doc_decoder: BlockDecoder::new(),
+            freq_decoder: BlockDecoder::with_val(1),
+            freq_reading_option,
+            doc_offset: 0,
+            doc_freq,
+            remaining_data: postings_data,
+            skip_reader,
+        }
+    }
+
+    // Resets the block segment postings on another position
+    // in the postings file.
+    //
+    // This is useful for enumerating through a list of terms,
+    // and consuming the associated posting lists while avoiding
+    // reallocating a `BlockSegmentPostings`.
+    //
+    // # Warning
+    //
+    // This does not reset the positions list.
+    pub(crate) fn reset(&mut self, doc_freq: u32, postings_data: OwnedRead) {
+        let (skip_data_opt, postings_data) = split_into_skips_and_postings(doc_freq, postings_data);
+        let num_vint_docs = (doc_freq as usize) & (COMPRESSION_BLOCK_SIZE - 1);
+        self.num_vint_docs = num_vint_docs;
+        self.remaining_data = postings_data;
+        if let Some(skip_data) = skip_data_opt {
+            self.skip_reader.reset(skip_data);
+        } else {
+            self.skip_reader.reset(OwnedRead::new(&[][..]))
+        }
+        self.doc_offset = 0;
+        self.doc_freq = doc_freq as usize;
+    }
+
+    /// Returns the document frequency associated to this block postings.
+    ///
+    /// This `doc_freq` is simply the sum of the length of all of the blocks
+    /// length, and it does not take in account deleted documents.
+    pub fn doc_freq(&self) -> usize {
+        self.doc_freq
+    }
+
+    /// Returns the array of docs in the current block.
+    ///
+    /// Before the first call to `.advance()`, the block
+    /// returned by `.docs()` is empty.
+    #[inline]
+    pub fn docs(&self) -> &[DocId] {
+        self.doc_decoder.output_array()
+    }
+
+    pub(crate) fn docs_aligned(&self) -> (&AlignedBuffer, usize) {
+        self.doc_decoder.output_aligned()
+    }
+
+    /// Return the document at index `idx` of the block.
+    #[inline]
+    pub fn doc(&self, idx: usize) -> u32 {
+        self.doc_decoder.output(idx)
+    }
+
+    /// Return the array of `term freq` in the block.
+    #[inline]
+    pub fn freqs(&self) -> &[u32] {
+        self.freq_decoder.output_array()
+    }
+
+    /// Return the frequency at index `idx` of the block.
+    #[inline]
+    pub fn freq(&self, idx: usize) -> u32 {
+        self.freq_decoder.output(idx)
+    }
+
+    /// Returns the length of the current block.
+    ///
+    /// All blocks have a length of `NUM_DOCS_PER_BLOCK`,
+    /// except the last block that may have a length
+    /// of any number between 1 and `NUM_DOCS_PER_BLOCK - 1`
+    #[inline]
+    fn block_len(&self) -> usize {
+        self.doc_decoder.output_len
+    }
+
+    /// position on a block that may contains `doc_id`.
+    /// Always advance the current block.
+    ///
+    /// Returns true if a block that has an element greater or equal to the target is found.
+    /// Returning true does not guarantee that the smallest element of the block is smaller
+    /// than the target. It only guarantees that the last element is greater or equal.
+    ///
+    /// Returns false iff all of the document remaining are smaller than
+    /// `doc_id`. In that case, all of these document are consumed.
+    ///
+    pub fn skip_to(&mut self, target_doc: DocId) -> BlockSegmentPostingsSkipResult {
+        let mut skip_freqs = 0u32;
+        while self.skip_reader.advance() {
+            if self.skip_reader.doc() >= target_doc {
+                // the last document of the current block is larger
+                // than the target.
+                //
+                // We found our block!
+                let num_bits = self.skip_reader.doc_num_bits();
+                let num_consumed_bytes = self.doc_decoder.uncompress_block_sorted(
+                    self.remaining_data.as_ref(),
+                    self.doc_offset,
+                    num_bits,
+                );
+                self.remaining_data.advance(num_consumed_bytes);
+                let tf_num_bits = self.skip_reader.tf_num_bits();
+                match self.freq_reading_option {
+                    FreqReadingOption::NoFreq => {}
+                    FreqReadingOption::SkipFreq => {
+                        let num_bytes_to_skip = compressed_block_size(tf_num_bits);
+                        self.remaining_data.advance(num_bytes_to_skip);
+                    }
+                    FreqReadingOption::ReadFreq => {
+                        let num_consumed_bytes = self
+                            .freq_decoder
+                            .uncompress_block_unsorted(self.remaining_data.as_ref(), tf_num_bits);
+                        self.remaining_data.advance(num_consumed_bytes);
+                    }
+                }
+                self.doc_offset = self.skip_reader.doc();
+                return BlockSegmentPostingsSkipResult::Success(skip_freqs);
+            } else {
+                skip_freqs += self.skip_reader.tf_sum();
+                let advance_len = self.skip_reader.total_block_len();
+                self.doc_offset = self.skip_reader.doc();
+                self.remaining_data.advance(advance_len);
+            }
+        }
+
+        // we are now on the last, incomplete, variable encoded block.
+        if self.num_vint_docs > 0 {
+            let num_compressed_bytes = self.doc_decoder.uncompress_vint_sorted(
+                self.remaining_data.as_ref(),
+                self.doc_offset,
+                self.num_vint_docs,
+            );
+            self.remaining_data.advance(num_compressed_bytes);
+            match self.freq_reading_option {
+                FreqReadingOption::NoFreq | FreqReadingOption::SkipFreq => {}
+                FreqReadingOption::ReadFreq => {
+                    self.freq_decoder
+                        .uncompress_vint_unsorted(self.remaining_data.as_ref(), self.num_vint_docs);
+                }
+            }
+            self.num_vint_docs = 0;
+            return self
+                .docs()
+                .last()
+                .map(|last_doc| {
+                    if *last_doc >= target_doc {
+                        BlockSegmentPostingsSkipResult::Success(skip_freqs)
+                    } else {
+                        BlockSegmentPostingsSkipResult::Terminated
+                    }
+                })
+                .unwrap_or(BlockSegmentPostingsSkipResult::Terminated);
+        }
+        BlockSegmentPostingsSkipResult::Terminated
+    }
+
+    /// Advance to the next block.
+    ///
+    /// Returns false iff there was no remaining blocks.
+    pub fn advance(&mut self) -> bool {
+        if self.skip_reader.advance() {
+            let num_bits = self.skip_reader.doc_num_bits();
+            let num_consumed_bytes = self.doc_decoder.uncompress_block_sorted(
+                self.remaining_data.as_ref(),
+                self.doc_offset,
+                num_bits,
+            );
+            self.remaining_data.advance(num_consumed_bytes);
+            let tf_num_bits = self.skip_reader.tf_num_bits();
+            match self.freq_reading_option {
+                FreqReadingOption::NoFreq => {}
+                FreqReadingOption::SkipFreq => {
+                    let num_bytes_to_skip = compressed_block_size(tf_num_bits);
+                    self.remaining_data.advance(num_bytes_to_skip);
+                }
+                FreqReadingOption::ReadFreq => {
+                    let num_consumed_bytes = self
+                        .freq_decoder
+                        .uncompress_block_unsorted(self.remaining_data.as_ref(), tf_num_bits);
+                    self.remaining_data.advance(num_consumed_bytes);
+                }
+            }
+            // it will be used as the next offset.
+            self.doc_offset = self.doc_decoder.output(COMPRESSION_BLOCK_SIZE - 1);
+            true
+        } else if self.num_vint_docs > 0 {
+            let num_compressed_bytes = self.doc_decoder.uncompress_vint_sorted(
+                self.remaining_data.as_ref(),
+                self.doc_offset,
+                self.num_vint_docs,
+            );
+            self.remaining_data.advance(num_compressed_bytes);
+            match self.freq_reading_option {
+                FreqReadingOption::NoFreq | FreqReadingOption::SkipFreq => {}
+                FreqReadingOption::ReadFreq => {
+                    self.freq_decoder
+                        .uncompress_vint_unsorted(self.remaining_data.as_ref(), self.num_vint_docs);
+                }
+            }
+            self.num_vint_docs = 0;
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Returns an empty segment postings object
+    pub fn empty() -> BlockSegmentPostings {
+        BlockSegmentPostings {
+            num_vint_docs: 0,
+
+            doc_decoder: BlockDecoder::new(),
+            freq_decoder: BlockDecoder::with_val(1),
+            freq_reading_option: FreqReadingOption::NoFreq,
+
+            doc_offset: 0,
+            doc_freq: 0,
+
+            remaining_data: OwnedRead::new(vec![]),
+            skip_reader: SkipReader::new(OwnedRead::new(vec![]), IndexRecordOption::Basic),
+        }
+    }
+}
+
+impl<'b> Streamer<'b> for BlockSegmentPostings {
+    type Item = &'b [DocId];
+
+    fn next(&'b mut self) -> Option<&'b [DocId]> {
+        if self.advance() {
+            Some(self.docs())
+        } else {
+            None
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
-
+    use super::BlockSegmentPostings;
+    use super::BlockSegmentPostingsSkipResult;
     use super::SegmentPostings;
     use crate::common::HasLen;
-
-    use crate::docset::{DocSet, TERMINATED};
-    use crate::fastfield::DeleteBitSet;
+    use crate::core::Index;
+    use crate::docset::DocSet;
     use crate::postings::postings::Postings;
+    use crate::schema::IndexRecordOption;
+    use crate::schema::Schema;
+    use crate::schema::Term;
+    use crate::schema::INDEXED;
+    use crate::DocId;
+    use crate::SkipResult;
+    use tantivy_fst::Streamer;
 
     #[test]
     fn test_empty_segment_postings() {
         let mut postings = SegmentPostings::empty();
-        assert_eq!(postings.advance(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
+        assert!(!postings.advance());
+        assert!(!postings.advance());
         assert_eq!(postings.len(), 0);
     }
 
     #[test]
-    fn test_empty_postings_doc_returns_terminated() {
-        let mut postings = SegmentPostings::empty();
-        assert_eq!(postings.doc(), TERMINATED);
-        assert_eq!(postings.advance(), TERMINATED);
+    #[should_panic(expected = "Have you forgotten to call `.advance()`")]
+    fn test_panic_if_doc_called_before_advance() {
+        SegmentPostings::empty().doc();
     }
 
     #[test]
-    fn test_empty_postings_doc_term_freq_returns_0() {
-        let postings = SegmentPostings::empty();
-        assert_eq!(postings.term_freq(), 1);
+    #[should_panic(expected = "Have you forgotten to call `.advance()`")]
+    fn test_panic_if_freq_called_before_advance() {
+        SegmentPostings::empty().term_freq();
     }
 
     #[test]
-    fn test_doc_freq() {
-        let docs = SegmentPostings::create_from_docs(&[0, 2, 10]);
-        assert_eq!(docs.doc_freq(), 3);
-        let delete_bitset = DeleteBitSet::for_test(&[2], 12);
-        assert_eq!(docs.doc_freq_given_deletes(&delete_bitset), 2);
-        let all_deleted = DeleteBitSet::for_test(&[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], 12);
-        assert_eq!(docs.doc_freq_given_deletes(&all_deleted), 0);
+    fn test_empty_block_segment_postings() {
+        let mut postings = BlockSegmentPostings::empty();
+        assert!(!postings.advance());
+        assert_eq!(postings.doc_freq(), 0);
+    }
+
+    #[test]
+    fn test_block_segment_postings() {
+        let mut block_segments = build_block_postings(&(0..100_000).collect::<Vec<u32>>());
+        let mut offset: u32 = 0u32;
+        // checking that the block before calling advance is empty
+        assert!(block_segments.docs().is_empty());
+        // checking that the `doc_freq` is correct
+        assert_eq!(block_segments.doc_freq(), 100_000);
+        while let Some(block) = block_segments.next() {
+            for (i, doc) in block.iter().cloned().enumerate() {
+                assert_eq!(offset + (i as u32), doc);
+            }
+            offset += block.len() as u32;
+        }
+    }
+
+    #[test]
+    fn test_skip_right_at_new_block() {
+        let mut doc_ids = (0..128).collect::<Vec<u32>>();
+        doc_ids.push(129);
+        doc_ids.push(130);
+        {
+            let block_segments = build_block_postings(&doc_ids);
+            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
+            assert_eq!(docset.skip_next(128), SkipResult::OverStep);
+            assert_eq!(docset.doc(), 129);
+            assert!(docset.advance());
+            assert_eq!(docset.doc(), 130);
+            assert!(!docset.advance());
+        }
+        {
+            let block_segments = build_block_postings(&doc_ids);
+            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
+            assert_eq!(docset.skip_next(129), SkipResult::Reached);
+            assert_eq!(docset.doc(), 129);
+            assert!(docset.advance());
+            assert_eq!(docset.doc(), 130);
+            assert!(!docset.advance());
+        }
+        {
+            let block_segments = build_block_postings(&doc_ids);
+            let mut docset = SegmentPostings::from_block_postings(block_segments, None);
+            assert_eq!(docset.skip_next(131), SkipResult::End);
+        }
+    }
+
+    fn build_block_postings(docs: &[DocId]) -> BlockSegmentPostings {
+        let mut schema_builder = Schema::builder();
+        let int_field = schema_builder.add_u64_field("id", INDEXED);
+        let schema = schema_builder.build();
+        let index = Index::create_in_ram(schema);
+        let mut index_writer = index.writer_with_num_threads(1, 3_000_000).unwrap();
+        let mut last_doc = 0u32;
+        for &doc in docs {
+            for _ in last_doc..doc {
+                index_writer.add_document(doc!(int_field=>1u64));
+            }
+            index_writer.add_document(doc!(int_field=>0u64));
+            last_doc = doc + 1;
+        }
+        index_writer.commit().unwrap();
+        let searcher = index.reader().unwrap().searcher();
+        let segment_reader = searcher.segment_reader(0);
+        let inverted_index = segment_reader.inverted_index(int_field);
+        let term = Term::from_field_u64(int_field, 0u64);
+        let term_info = inverted_index.get_term_info(&term).unwrap();
+        inverted_index.read_block_postings_from_terminfo(&term_info, IndexRecordOption::Basic)
+    }
+
+    #[test]
+    fn test_block_segment_postings_skip() {
+        for i in 0..4 {
+            let mut block_postings = build_block_postings(&[3]);
+            assert_eq!(
+                block_postings.skip_to(i),
+                BlockSegmentPostingsSkipResult::Success(0u32)
+            );
+            assert_eq!(
+                block_postings.skip_to(i),
+                BlockSegmentPostingsSkipResult::Terminated
+            );
+        }
+        let mut block_postings = build_block_postings(&[3]);
+        assert_eq!(
+            block_postings.skip_to(4u32),
+            BlockSegmentPostingsSkipResult::Terminated
+        );
+    }
+
+    #[test]
+    fn test_block_segment_postings_skip2() {
+        let mut docs = vec![0];
+        for i in 0..1300 {
+            docs.push((i * i / 100) + i);
+        }
+        let mut block_postings = build_block_postings(&docs[..]);
+        for i in vec![0, 424, 10000] {
+            assert_eq!(
+                block_postings.skip_to(i),
+                BlockSegmentPostingsSkipResult::Success(0u32)
+            );
+            let docs = block_postings.docs();
+            assert!(docs[0] <= i);
+            assert!(docs.last().cloned().unwrap_or(0u32) >= i);
+        }
+        assert_eq!(
+            block_postings.skip_to(100_000),
+            BlockSegmentPostingsSkipResult::Terminated
+        );
+        assert_eq!(
+            block_postings.skip_to(101_000),
+            BlockSegmentPostingsSkipResult::Terminated
+        );
+    }
+
+    #[test]
+    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_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().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();
+            block_segments = inverted_index
+                .read_block_postings_from_terminfo(&term_info, IndexRecordOption::Basic);
+        }
+        assert!(block_segments.advance());
+        assert_eq!(block_segments.docs(), &[0, 2, 4]);
+        {
+            let term = Term::from_field_u64(int_field, 1u64);
+            let inverted_index = segment_reader.inverted_index(int_field);
+            let term_info = inverted_index.get_term_info(&term).unwrap();
+            inverted_index.reset_block_postings_from_terminfo(&term_info, &mut block_segments);
+        }
+        assert!(block_segments.advance());
+        assert_eq!(block_segments.docs(), &[1, 3, 5]);
     }
 }

src/postings/serializer.rs

@@ -3,16 +3,14 @@ use crate::common::{BinarySerializable, VInt};
 use crate::common::{CompositeWrite, CountingWriter};
 use crate::core::Segment;
 use crate::directory::WritePtr;
-use crate::fieldnorm::FieldNormReader;
 use crate::positions::PositionSerializer;
 use crate::postings::compression::{BlockEncoder, VIntEncoder, COMPRESSION_BLOCK_SIZE};
 use crate::postings::skip::SkipSerializer;
-use crate::query::BM25Weight;
+use crate::postings::USE_SKIP_INFO_LIMIT;
 use crate::schema::Schema;
 use crate::schema::{Field, FieldEntry, FieldType};
 use crate::termdict::{TermDictionaryBuilder, TermOrdinal};
-use crate::{DocId, Score};
-use std::cmp::Ordering;
+use crate::DocId;
 use std::io::{self, Write};
 
 /// `InvertedIndexSerializer` is in charge of serializing
@@ -92,22 +90,20 @@ impl InvertedIndexSerializer {
         &mut self,
         field: Field,
         total_num_tokens: u64,
-        fieldnorm_reader: Option<FieldNormReader>,
     ) -> io::Result<FieldSerializer<'_>> {
         let field_entry: &FieldEntry = self.schema.get_field_entry(field);
         let term_dictionary_write = self.terms_write.for_field(field);
         let postings_write = self.postings_write.for_field(field);
+        total_num_tokens.serialize(postings_write)?;
         let positions_write = self.positions_write.for_field(field);
         let positionsidx_write = self.positionsidx_write.for_field(field);
         let field_type: FieldType = (*field_entry.field_type()).clone();
         FieldSerializer::create(
             &field_type,
-            total_num_tokens,
             term_dictionary_write,
             postings_write,
             positions_write,
             positionsidx_write,
-            fieldnorm_reader,
         )
     }
 
@@ -135,14 +131,11 @@ pub struct FieldSerializer<'a> {
 impl<'a> FieldSerializer<'a> {
     fn create(
         field_type: &FieldType,
-        total_num_tokens: u64,
         term_dictionary_write: &'a mut CountingWriter<WritePtr>,
         postings_write: &'a mut CountingWriter<WritePtr>,
         positions_write: &'a mut CountingWriter<WritePtr>,
         positionsidx_write: &'a mut CountingWriter<WritePtr>,
-        fieldnorm_reader: Option<FieldNormReader>,
     ) -> io::Result<FieldSerializer<'a>> {
-        total_num_tokens.serialize(postings_write)?;
         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() {
@@ -155,17 +148,8 @@ impl<'a> FieldSerializer<'a> {
             _ => (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,
-            term_freq_enabled,
-            position_enabled,
-            fieldnorm_reader,
-        );
+        let postings_serializer =
+            PostingsSerializer::new(postings_write, term_freq_enabled, position_enabled);
         let positions_serializer_opt = if position_enabled {
             Some(PositionSerializer::new(positions_write, positionsidx_write))
         } else {
@@ -198,20 +182,18 @@ impl<'a> FieldSerializer<'a> {
     /// Starts the postings for a new term.
     /// * term - the term. It needs to come after the previous term according
     ///   to the lexicographical order.
-    /// * term_doc_freq - return the number of document containing the term.
-    pub fn new_term(&mut self, term: &[u8], term_doc_freq: u32) -> io::Result<TermOrdinal> {
+    /// * doc_freq - return the number of document containing the term.
+    pub fn new_term(&mut self, term: &[u8]) -> io::Result<TermOrdinal> {
         assert!(
             !self.term_open,
             "Called new_term, while the previous term was not closed."
         );
-
         self.term_open = true;
         self.postings_serializer.clear();
         self.current_term_info = self.current_term_info();
         self.term_dictionary_builder.insert_key(term)?;
         let term_ordinal = self.num_terms;
         self.num_terms += 1;
-        self.postings_serializer.new_term(term_doc_freq);
         Ok(term_ordinal)
     }
 
@@ -325,27 +307,14 @@ pub struct PostingsSerializer<W: Write> {
 
     termfreq_enabled: bool,
     termfreq_sum_enabled: bool,
-    fieldnorm_reader: Option<FieldNormReader>,
-
-    bm25_weight: Option<BM25Weight>,
-
-    num_docs: u32, // Number of docs in the segment
-    avg_fieldnorm: Score, // Average number of term in the field for that segment.
-                   // this value is used to compute the block wand information.
 }
 
 impl<W: Write> PostingsSerializer<W> {
     pub fn new(
         write: W,
-        avg_fieldnorm: Score,
         termfreq_enabled: bool,
         termfreq_sum_enabled: bool,
-        fieldnorm_reader: Option<FieldNormReader>,
     ) -> PostingsSerializer<W> {
-        let num_docs = fieldnorm_reader
-            .as_ref()
-            .map(|fieldnorm_reader| fieldnorm_reader.num_docs())
-            .unwrap_or(0u32);
         PostingsSerializer {
             output_write: CountingWriter::wrap(write),
 
@@ -358,23 +327,6 @@ impl<W: Write> PostingsSerializer<W> {
             last_doc_id_encoded: 0u32,
             termfreq_enabled,
             termfreq_sum_enabled,
-
-            fieldnorm_reader,
-            bm25_weight: None,
-
-            num_docs,
-            avg_fieldnorm,
-        }
-    }
-
-    pub fn new_term(&mut self, term_doc_freq: u32) {
-        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,
-                self.avg_fieldnorm,
-            );
-            self.bm25_weight = Some(bm25_weight);
         }
     }
 
@@ -391,6 +343,7 @@ impl<W: Write> PostingsSerializer<W> {
             self.postings_write.extend(block_encoded);
         }
         if self.termfreq_enabled {
+            // encode the term_freqs
             let (num_bits, block_encoded): (u8, &[u8]) = self
                 .block_encoder
                 .compress_block_unsorted(&self.block.term_freqs());
@@ -400,31 +353,6 @@ impl<W: Write> PostingsSerializer<W> {
                 let sum_freq = self.block.term_freqs().iter().cloned().sum();
                 self.skip_write.write_total_term_freq(sum_freq);
             }
-            let mut blockwand_params = (0u8, 0u32);
-            if let Some(bm25_weight) = self.bm25_weight.as_ref() {
-                if let Some(fieldnorm_reader) = self.fieldnorm_reader.as_ref() {
-                    let docs = self.block.doc_ids().iter().cloned();
-                    let term_freqs = self.block.term_freqs().iter().cloned();
-                    let fieldnorms = docs.map(|doc| fieldnorm_reader.fieldnorm_id(doc));
-                    blockwand_params = fieldnorms
-                        .zip(term_freqs)
-                        .max_by(
-                            |(left_fieldnorm_id, left_term_freq),
-                             (right_fieldnorm_id, right_term_freq)| {
-                                let left_score =
-                                    bm25_weight.tf_factor(*left_fieldnorm_id, *left_term_freq);
-                                let right_score =
-                                    bm25_weight.tf_factor(*right_fieldnorm_id, *right_term_freq);
-                                left_score
-                                    .partial_cmp(&right_score)
-                                    .unwrap_or(Ordering::Equal)
-                            },
-                        )
-                        .unwrap();
-                }
-            }
-            let (fieldnorm_id, term_freq) = blockwand_params;
-            self.skip_write.write_blockwand_max(fieldnorm_id, term_freq);
         }
         self.block.clear();
     }
@@ -463,7 +391,7 @@ impl<W: Write> PostingsSerializer<W> {
             }
             self.block.clear();
         }
-        if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
+        if doc_freq >= USE_SKIP_INFO_LIMIT {
             let skip_data = self.skip_write.data();
             VInt(skip_data.len() as u64).serialize(&mut self.output_write)?;
             self.output_write.write_all(skip_data)?;
@@ -473,7 +401,6 @@ impl<W: Write> PostingsSerializer<W> {
         }
         self.skip_write.clear();
         self.postings_write.clear();
-        self.bm25_weight = None;
         Ok(())
     }
 

src/postings/skip.rs

@@ -1,9 +1,7 @@
-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::common::BinarySerializable;
+use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
 use crate::schema::IndexRecordOption;
-use crate::{DocId, Score, TERMINATED};
+use crate::DocId;
 use owned_read::OwnedRead;
 
 pub struct SkipSerializer {
@@ -41,13 +39,6 @@ impl SkipSerializer {
             .expect("Should never fail");
     }
 
-    pub fn write_blockwand_max(&mut self, fieldnorm_id: u8, term_freq: u32) {
-        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] {
         &self.buffer[..]
     }
@@ -58,200 +49,81 @@ impl SkipSerializer {
     }
 }
 
-#[derive(Clone)]
 pub(crate) struct SkipReader {
-    last_doc_in_block: DocId,
-    pub(crate) last_doc_in_previous_block: DocId,
+    doc: DocId,
     owned_read: OwnedRead,
+    doc_num_bits: u8,
+    tf_num_bits: u8,
+    tf_sum: u32,
     skip_info: IndexRecordOption,
-    byte_offset: usize,
-    remaining_docs: u32, // number of docs remaining, including the
-    // documents in the current block.
-    block_info: BlockInfo,
-
-    position_offset: u64,
-}
-
-#[derive(Clone, Eq, PartialEq, Copy, Debug)]
-pub(crate) enum BlockInfo {
-    BitPacked {
-        doc_num_bits: u8,
-        tf_num_bits: u8,
-        tf_sum: u32,
-        block_wand_fieldnorm_id: u8,
-        block_wand_term_freq: u32,
-    },
-    VInt {
-        num_docs: u32,
-    },
-}
-
-impl Default for BlockInfo {
-    fn default() -> Self {
-        BlockInfo::VInt { num_docs: 0u32 }
-    }
 }
 
 impl 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
-            } else {
-                TERMINATED
-            },
-            last_doc_in_previous_block: 0u32,
-            owned_read: OwnedRead::new(data),
+    pub fn new(data: OwnedRead, skip_info: IndexRecordOption) -> SkipReader {
+        SkipReader {
+            doc: 0u32,
+            owned_read: data,
             skip_info,
-            block_info: BlockInfo::VInt { num_docs: doc_freq },
-            byte_offset: 0,
-            remaining_docs: doc_freq,
-            position_offset: 0u64,
-        };
-        if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
-            skip_reader.read_block_info();
-        }
-        skip_reader
-    }
-
-    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 = OwnedRead::new(data);
-        self.block_info = BlockInfo::VInt { num_docs: doc_freq };
-        self.byte_offset = 0;
-        self.remaining_docs = doc_freq;
-        self.position_offset = 0u64;
-        if doc_freq >= COMPRESSION_BLOCK_SIZE as u32 {
-            self.read_block_info();
+            doc_num_bits: 0u8,
+            tf_num_bits: 0u8,
+            tf_sum: 0u32,
         }
     }
 
-    // Returns the block max score for this block if available.
-    //
-    // The block max score is available for all full bitpacked block,
-    // but no available for the last VInt encoded incomplete block.
-    pub fn block_max_score(&self, bm25_weight: &BM25Weight) -> Option<Score> {
-        match self.block_info {
-            BlockInfo::BitPacked {
-                block_wand_fieldnorm_id,
-                block_wand_term_freq,
-                ..
-            } => Some(bm25_weight.score(block_wand_fieldnorm_id, block_wand_term_freq)),
-            BlockInfo::VInt { .. } => None,
-        }
+    pub fn reset(&mut self, data: OwnedRead) {
+        self.doc = 0u32;
+        self.owned_read = data;
+        self.doc_num_bits = 0u8;
+        self.tf_num_bits = 0u8;
+        self.tf_sum = 0u32;
     }
 
-    pub(crate) fn last_doc_in_block(&self) -> DocId {
-        self.last_doc_in_block
+    pub fn total_block_len(&self) -> usize {
+        (self.doc_num_bits + self.tf_num_bits) as usize * COMPRESSION_BLOCK_SIZE / 8
     }
 
-    pub fn position_offset(&self) -> u64 {
-        self.position_offset
+    pub fn doc(&self) -> DocId {
+        self.doc
     }
 
-    pub fn byte_offset(&self) -> usize {
-        self.byte_offset
+    pub fn doc_num_bits(&self) -> u8 {
+        self.doc_num_bits
     }
 
-    fn read_block_info(&mut self) {
-        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 => {
-                self.owned_read.advance(1);
-                self.block_info = BlockInfo::BitPacked {
-                    doc_num_bits,
-                    tf_num_bits: 0,
-                    tf_sum: 0,
-                    block_wand_fieldnorm_id: 0,
-                    block_wand_term_freq: 0,
-                };
-            }
-            IndexRecordOption::WithFreqs => {
-                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,
-                    tf_sum: 0,
-                    block_wand_fieldnorm_id,
-                    block_wand_term_freq,
-                };
-            }
-            IndexRecordOption::WithFreqsAndPositions => {
-                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,
-                    tf_sum,
-                    block_wand_fieldnorm_id,
-                    block_wand_term_freq,
-                };
-            }
-        }
-    }
-
-    pub fn block_info(&self) -> BlockInfo {
-        self.block_info
-    }
-
-    /// Advance the skip reader to the block that may contain the target.
+    /// Number of bits used to encode term frequencies
     ///
-    /// If the target is larger than all documents, the skip_reader
-    /// then advance to the last Variable In block.
-    pub fn seek(&mut self, target: DocId) -> bool {
-        if self.last_doc_in_block() >= target {
-            return false;
-        }
-        loop {
-            self.advance();
-            if self.last_doc_in_block() >= target {
-                return true;
-            }
-        }
+    /// 0 if term frequencies are not enabled.
+    pub fn tf_num_bits(&self) -> u8 {
+        self.tf_num_bits
     }
 
-    pub fn advance(&mut self) {
-        match self.block_info {
-            BlockInfo::BitPacked {
-                doc_num_bits,
-                tf_num_bits,
-                tf_sum,
-                ..
-            } => {
-                self.remaining_docs -= COMPRESSION_BLOCK_SIZE as u32;
-                self.byte_offset += compressed_block_size(doc_num_bits + tf_num_bits);
-                self.position_offset += tf_sum as u64;
-            }
-            BlockInfo::VInt { num_docs } => {
-                debug_assert_eq!(num_docs, self.remaining_docs);
-                self.remaining_docs = 0;
-                self.byte_offset = std::usize::MAX;
-            }
-        }
-        self.last_doc_in_previous_block = self.last_doc_in_block;
-        if self.remaining_docs >= COMPRESSION_BLOCK_SIZE as u32 {
-            self.read_block_info();
+    pub fn tf_sum(&self) -> u32 {
+        self.tf_sum
+    }
+
+    pub fn advance(&mut self) -> bool {
+        if self.owned_read.as_ref().is_empty() {
+            false
         } else {
-            self.last_doc_in_block = TERMINATED;
-            self.block_info = BlockInfo::VInt {
-                num_docs: self.remaining_docs,
-            };
+            let doc_delta = u32::deserialize(&mut self.owned_read).expect("Skip data corrupted");
+            self.doc += doc_delta as DocId;
+            self.doc_num_bits = self.owned_read.get(0);
+            match self.skip_info {
+                IndexRecordOption::Basic => {
+                    self.owned_read.advance(1);
+                }
+                IndexRecordOption::WithFreqs => {
+                    self.tf_num_bits = self.owned_read.get(1);
+                    self.owned_read.advance(2);
+                }
+                IndexRecordOption::WithFreqsAndPositions => {
+                    self.tf_num_bits = self.owned_read.get(1);
+                    self.owned_read.advance(2);
+                    self.tf_sum =
+                        u32::deserialize(&mut self.owned_read).expect("Failed reading tf_sum");
+                }
+            }
+            true
         }
     }
 }
@@ -259,11 +131,9 @@ impl SkipReader {
 #[cfg(test)]
 mod tests {
 
-    use super::BlockInfo;
     use super::IndexRecordOption;
     use super::{SkipReader, SkipSerializer};
-    use crate::directory::ReadOnlySource;
-    use crate::postings::compression::COMPRESSION_BLOCK_SIZE;
+    use owned_read::OwnedRead;
 
     #[test]
     fn test_skip_with_freq() {
@@ -271,47 +141,20 @@ mod tests {
             let mut skip_serializer = SkipSerializer::new();
             skip_serializer.write_doc(1u32, 2u8);
             skip_serializer.write_term_freq(3u8);
-            skip_serializer.write_blockwand_max(13u8, 3u32);
             skip_serializer.write_doc(5u32, 5u8);
             skip_serializer.write_term_freq(2u8);
-            skip_serializer.write_blockwand_max(8u8, 2u32);
             skip_serializer.data().to_owned()
         };
-        let doc_freq = 3u32 + (COMPRESSION_BLOCK_SIZE * 2) as u32;
-        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,
-            BlockInfo::BitPacked {
-                doc_num_bits: 2u8,
-                tf_num_bits: 3u8,
-                tf_sum: 0,
-                block_wand_fieldnorm_id: 13,
-                block_wand_term_freq: 3
-            }
-        );
-        skip_reader.advance();
-        assert_eq!(skip_reader.last_doc_in_block(), 5u32);
-        assert_eq!(
-            skip_reader.block_info(),
-            BlockInfo::BitPacked {
-                doc_num_bits: 5u8,
-                tf_num_bits: 2u8,
-                tf_sum: 0,
-                block_wand_fieldnorm_id: 8,
-                block_wand_term_freq: 2
-            }
-        );
-        skip_reader.advance();
-        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 3u32 });
-        skip_reader.advance();
-        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
-        skip_reader.advance();
-        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
+        let mut skip_reader = SkipReader::new(OwnedRead::new(buf), IndexRecordOption::WithFreqs);
+        assert!(skip_reader.advance());
+        assert_eq!(skip_reader.doc(), 1u32);
+        assert_eq!(skip_reader.doc_num_bits(), 2u8);
+        assert_eq!(skip_reader.tf_num_bits(), 3u8);
+        assert!(skip_reader.advance());
+        assert_eq!(skip_reader.doc(), 5u32);
+        assert_eq!(skip_reader.doc_num_bits(), 5u8);
+        assert_eq!(skip_reader.tf_num_bits(), 2u8);
+        assert!(!skip_reader.advance());
     }
 
     #[test]
@@ -322,68 +165,13 @@ mod tests {
             skip_serializer.write_doc(5u32, 5u8);
             skip_serializer.data().to_owned()
         };
-        let doc_freq = 3u32 + (COMPRESSION_BLOCK_SIZE * 2) as u32;
-        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(),
-            BlockInfo::BitPacked {
-                doc_num_bits: 2u8,
-                tf_num_bits: 0,
-                tf_sum: 0u32,
-                block_wand_fieldnorm_id: 0,
-                block_wand_term_freq: 0
-            }
-        );
-        skip_reader.advance();
-        assert_eq!(skip_reader.last_doc_in_block(), 5u32);
-        assert_eq!(
-            skip_reader.block_info(),
-            BlockInfo::BitPacked {
-                doc_num_bits: 5u8,
-                tf_num_bits: 0,
-                tf_sum: 0u32,
-                block_wand_fieldnorm_id: 0,
-                block_wand_term_freq: 0
-            }
-        );
-        skip_reader.advance();
-        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 3u32 });
-        skip_reader.advance();
-        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
-        skip_reader.advance();
-        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
-    }
-
-    #[test]
-    fn test_skip_multiple_of_block_size() {
-        let buf = {
-            let mut skip_serializer = SkipSerializer::new();
-            skip_serializer.write_doc(1u32, 2u8);
-            skip_serializer.data().to_owned()
-        };
-        let doc_freq = COMPRESSION_BLOCK_SIZE as u32;
-        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(),
-            BlockInfo::BitPacked {
-                doc_num_bits: 2u8,
-                tf_num_bits: 0,
-                tf_sum: 0u32,
-                block_wand_fieldnorm_id: 0,
-                block_wand_term_freq: 0
-            }
-        );
-        skip_reader.advance();
-        assert_eq!(skip_reader.block_info(), BlockInfo::VInt { num_docs: 0u32 });
+        let mut skip_reader = SkipReader::new(OwnedRead::new(buf), IndexRecordOption::Basic);
+        assert!(skip_reader.advance());
+        assert_eq!(skip_reader.doc(), 1u32);
+        assert_eq!(skip_reader.doc_num_bits(), 2u8);
+        assert!(skip_reader.advance());
+        assert_eq!(skip_reader.doc(), 5u32);
+        assert_eq!(skip_reader.doc_num_bits(), 5u8);
+        assert!(!skip_reader.advance());
     }
 }

src/postings/stacker/memory_arena.rs

@@ -106,8 +106,8 @@ impl MemoryArena {
     ///
     /// Internally, it counts a number of `1MB` pages
     /// and therefore delivers an upperbound.
-    pub fn mem_usage(&self) -> usize {
-        self.pages.len() * PAGE_SIZE
+    pub fn mem_usage(&self) -> u64 {
+        (self.pages.len() as u64) * (PAGE_SIZE as u64)
     }
 
     pub fn write_at<Item: Copy + 'static>(&mut self, addr: Addr, val: Item) {

src/postings/stacker/term_hashmap.rs

@@ -1,4 +1,6 @@
-use murmurhash32::murmurhash2;
+use murmurhash32;
+
+use self::murmurhash32::murmurhash2;
 
 use super::{Addr, MemoryArena};
 use crate::postings::stacker::memory_arena::store;
@@ -10,8 +12,8 @@ use std::slice;
 
 /// Returns the actual memory size in bytes
 /// required to create a table of size $2^num_bits$.
-pub fn compute_table_size(num_bits: usize) -> usize {
-    (1 << num_bits) * mem::size_of::<KeyValue>()
+pub fn compute_table_size(num_bits: usize) -> u64 {
+    (1u64 << num_bits as u64) * mem::size_of::<KeyValue>() as u64
 }
 
 /// `KeyValue` is the item stored in the hash table.
@@ -114,8 +116,8 @@ impl TermHashMap {
         QuadraticProbing::compute(hash as usize, self.mask)
     }
 
-    pub fn mem_usage(&self) -> usize {
-        self.table.len() * mem::size_of::<KeyValue>()
+    pub fn mem_usage(&self) -> u64 {
+        self.table.len() as u64 * mem::size_of::<KeyValue>() as u64
     }
 
     fn is_saturated(&self) -> bool {

src/query/all_query.rs

@@ -1,6 +1,6 @@
 use crate::core::Searcher;
 use crate::core::SegmentReader;
-use crate::docset::{DocSet, TERMINATED};
+use crate::docset::DocSet;
 use crate::query::boost_query::BoostScorer;
 use crate::query::explanation::does_not_match;
 use crate::query::{Explanation, Query, Scorer, Weight};
@@ -9,7 +9,7 @@ use crate::Score;
 
 /// Query that matches all of the documents.
 ///
-/// All of the document get the score 1.0.
+/// All of the document get the score 1f32.
 #[derive(Clone, Debug)]
 pub struct AllQuery;
 
@@ -23,8 +23,9 @@ impl Query for AllQuery {
 pub struct AllWeight;
 
 impl Weight for AllWeight {
-    fn scorer(&self, reader: &SegmentReader, boost: Score) -> crate::Result<Box<dyn Scorer>> {
+    fn scorer(&self, reader: &SegmentReader, boost: f32) -> crate::Result<Box<dyn Scorer>> {
         let all_scorer = AllScorer {
+            state: State::NotStarted,
             doc: 0u32,
             max_doc: reader.max_doc(),
         };
@@ -35,24 +36,43 @@ impl Weight for AllWeight {
         if doc >= reader.max_doc() {
             return Err(does_not_match(doc));
         }
-        Ok(Explanation::new("AllQuery", 1.0))
+        Ok(Explanation::new("AllQuery", 1f32))
     }
 }
 
+enum State {
+    NotStarted,
+    Started,
+    Finished,
+}
+
 /// Scorer associated to the `AllQuery` query.
 pub struct AllScorer {
+    state: State,
     doc: DocId,
     max_doc: DocId,
 }
 
 impl DocSet for AllScorer {
-    fn advance(&mut self) -> DocId {
-        if self.doc + 1 >= self.max_doc {
-            self.doc = TERMINATED;
-            return TERMINATED;
+    fn advance(&mut self) -> bool {
+        match self.state {
+            State::NotStarted => {
+                self.state = State::Started;
+                self.doc = 0;
+            }
+            State::Started => {
+                self.doc += 1u32;
+            }
+            State::Finished => {
+                return false;
+            }
+        }
+        if self.doc < self.max_doc {
+            true
+        } else {
+            self.state = State::Finished;
+            false
         }
-        self.doc += 1;
-        self.doc
     }
 
     fn doc(&self) -> DocId {
@@ -66,14 +86,13 @@ impl DocSet for AllScorer {
 
 impl Scorer for AllScorer {
     fn score(&mut self) -> Score {
-        1.0
+        1f32
     }
 }
 
 #[cfg(test)]
 mod tests {
     use super::AllQuery;
-    use crate::docset::TERMINATED;
     use crate::query::Query;
     use crate::schema::{Schema, TEXT};
     use crate::Index;
@@ -83,7 +102,7 @@ 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();
@@ -100,17 +119,19 @@ mod tests {
         let weight = AllQuery.weight(&searcher, false).unwrap();
         {
             let reader = searcher.segment_reader(0);
-            let mut scorer = weight.scorer(reader, 1.0).unwrap();
+            let mut scorer = weight.scorer(reader, 1.0f32).unwrap();
+            assert!(scorer.advance());
             assert_eq!(scorer.doc(), 0u32);
-            assert_eq!(scorer.advance(), 1u32);
+            assert!(scorer.advance());
             assert_eq!(scorer.doc(), 1u32);
-            assert_eq!(scorer.advance(), TERMINATED);
+            assert!(!scorer.advance());
         }
         {
             let reader = searcher.segment_reader(1);
-            let mut scorer = weight.scorer(reader, 1.0).unwrap();
+            let mut scorer = weight.scorer(reader, 1.0f32).unwrap();
+            assert!(scorer.advance());
             assert_eq!(scorer.doc(), 0u32);
-            assert_eq!(scorer.advance(), TERMINATED);
+            assert!(!scorer.advance());
         }
     }
 
@@ -122,14 +143,16 @@ mod tests {
         let weight = AllQuery.weight(&searcher, false).unwrap();
         let reader = searcher.segment_reader(0);
         {
-            let mut scorer = weight.scorer(reader, 2.0).unwrap();
+            let mut scorer = weight.scorer(reader, 2.0f32).unwrap();
+            assert!(scorer.advance());
             assert_eq!(scorer.doc(), 0u32);
-            assert_eq!(scorer.score(), 2.0);
+            assert_eq!(scorer.score(), 2.0f32);
         }
         {
-            let mut scorer = weight.scorer(reader, 1.5).unwrap();
+            let mut scorer = weight.scorer(reader, 1.5f32).unwrap();
+            assert!(scorer.advance());
             assert_eq!(scorer.doc(), 0u32);
-            assert_eq!(scorer.score(), 1.5);
+            assert_eq!(scorer.score(), 1.5f32);
         }
     }
 }

src/query/automaton_weight.rs

@@ -5,8 +5,9 @@ use crate::query::{BitSetDocSet, Explanation};
 use crate::query::{Scorer, Weight};
 use crate::schema::{Field, IndexRecordOption};
 use crate::termdict::{TermDictionary, TermStreamer};
+use crate::DocId;
 use crate::TantivyError;
-use crate::{DocId, Score};
+use crate::{Result, SkipResult};
 use std::sync::Arc;
 use tantivy_fst::Automaton;
 
@@ -39,9 +40,10 @@ impl<A> Weight for AutomatonWeight<A>
 where
     A: Automaton + Send + Sync + 'static,
 {
-    fn scorer(&self, reader: &SegmentReader, boost: Score) -> crate::Result<Box<dyn Scorer>> {
+    fn scorer(&self, reader: &SegmentReader, boost: f32) -> 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 term_dict = inverted_index.terms();
         let mut term_stream = self.automaton_stream(term_dict);
@@ -49,15 +51,10 @@ where
             let term_info = term_stream.value();
             let mut block_segment_postings = inverted_index
                 .read_block_postings_from_terminfo(term_info, IndexRecordOption::Basic);
-            loop {
-                let docs = block_segment_postings.docs();
-                if docs.is_empty() {
-                    break;
-                }
-                for &doc in docs {
+            while block_segment_postings.advance() {
+                for &doc in block_segment_postings.docs() {
                     doc_bitset.insert(doc);
                 }
-                block_segment_postings.advance();
             }
         }
         let doc_bitset = BitSetDocSet::from(doc_bitset);
@@ -65,10 +62,10 @@ where
         Ok(Box::new(const_scorer))
     }
 
-    fn explain(&self, reader: &SegmentReader, doc: DocId) -> crate::Result<Explanation> {
-        let mut scorer = self.scorer(reader, 1.0)?;
-        if scorer.seek(doc) == doc {
-            Ok(Explanation::new("AutomatonScorer", 1.0))
+    fn explain(&self, reader: &SegmentReader, doc: DocId) -> Result<Explanation> {
+        let mut scorer = self.scorer(reader, 1.0f32)?;
+        if scorer.skip_next(doc) == SkipResult::Reached {
+            Ok(Explanation::new("AutomatonScorer", 1.0f32))
         } else {
             Err(TantivyError::InvalidArgument(
                 "Document does not exist".to_string(),
@@ -80,7 +77,6 @@ where
 #[cfg(test)]
 mod tests {
     use super::AutomatonWeight;
-    use crate::docset::TERMINATED;
     use crate::query::Weight;
     use crate::schema::{Schema, STRING};
     use crate::Index;
@@ -90,7 +86,7 @@ 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"));
@@ -143,14 +139,15 @@ mod tests {
         let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let mut scorer = automaton_weight
-            .scorer(searcher.segment_reader(0u32), 1.0)
+            .scorer(searcher.segment_reader(0u32), 1.0f32)
             .unwrap();
+        assert!(scorer.advance());
         assert_eq!(scorer.doc(), 0u32);
-        assert_eq!(scorer.score(), 1.0);
-        assert_eq!(scorer.advance(), 2u32);
+        assert_eq!(scorer.score(), 1.0f32);
+        assert!(scorer.advance());
         assert_eq!(scorer.doc(), 2u32);
-        assert_eq!(scorer.score(), 1.0);
-        assert_eq!(scorer.advance(), TERMINATED);
+        assert_eq!(scorer.score(), 1.0f32);
+        assert!(!scorer.advance());
     }
 
     #[test]
@@ -161,9 +158,10 @@ mod tests {
         let reader = index.reader().unwrap();
         let searcher = reader.searcher();
         let mut scorer = automaton_weight
-            .scorer(searcher.segment_reader(0u32), 1.32)
+            .scorer(searcher.segment_reader(0u32), 1.32f32)
             .unwrap();
+        assert!(scorer.advance());
         assert_eq!(scorer.doc(), 0u32);
-        assert_eq!(scorer.score(), 1.32);
+        assert_eq!(scorer.score(), 1.32f32);
     }
 }

src/query/bitset/mod.rs

@@ -1,6 +1,7 @@
 use crate::common::{BitSet, TinySet};
-use crate::docset::{DocSet, TERMINATED};
+use crate::docset::{DocSet, SkipResult};
 use crate::DocId;
+use std::cmp::Ordering;
 
 /// A `BitSetDocSet` makes it possible to iterate through a bitset as if it was a `DocSet`.
 ///
@@ -32,51 +33,74 @@ impl From<BitSet> for BitSetDocSet {
         } else {
             docs.tinyset(0)
         };
-        let mut docset = BitSetDocSet {
+        BitSetDocSet {
             docs,
             cursor_bucket: 0,
             cursor_tinybitset: first_tiny_bitset,
             doc: 0u32,
-        };
-        docset.advance();
-        docset
+        }
     }
 }
 
 impl DocSet for BitSetDocSet {
-    fn advance(&mut self) -> DocId {
+    fn advance(&mut self) -> bool {
         if let Some(lower) = self.cursor_tinybitset.pop_lowest() {
             self.doc = (self.cursor_bucket as u32 * 64u32) | lower;
-            return self.doc;
+            return true;
         }
         if let Some(cursor_bucket) = self.docs.first_non_empty_bucket(self.cursor_bucket + 1) {
             self.go_to_bucket(cursor_bucket);
             let lower = self.cursor_tinybitset.pop_lowest().unwrap();
             self.doc = (cursor_bucket * 64u32) | lower;
-            self.doc
+            true
         } else {
-            self.doc = TERMINATED;
-            TERMINATED
+            false
         }
     }
 
-    fn seek(&mut self, target: DocId) -> DocId {
-        if target >= self.docs.max_value() {
-            self.doc = TERMINATED;
-            return TERMINATED;
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
+        // skip is required to advance.
+        if !self.advance() {
+            return SkipResult::End;
         }
         let target_bucket = target / 64u32;
-        if target_bucket > self.cursor_bucket {
-            self.go_to_bucket(target_bucket);
-            let greater_filter: TinySet = TinySet::range_greater_or_equal(target);
-            self.cursor_tinybitset = self.cursor_tinybitset.intersect(greater_filter);
-            self.advance()
-        } else {
-            let mut doc = self.doc();
-            while doc < target {
-                doc = self.advance();
+
+        // Mask for all of the bits greater or equal
+        // to our target document.
+        match target_bucket.cmp(&self.cursor_bucket) {
+            Ordering::Greater => {
+                self.go_to_bucket(target_bucket);
+                let greater_filter: TinySet = TinySet::range_greater_or_equal(target);
+                self.cursor_tinybitset = self.cursor_tinybitset.intersect(greater_filter);
+                if !self.advance() {
+                    SkipResult::End
+                } else if self.doc() == target {
+                    SkipResult::Reached
+                } else {
+                    debug_assert!(self.doc() > target);
+                    SkipResult::OverStep
+                }
+            }
+            Ordering::Equal => loop {
+                match self.doc().cmp(&target) {
+                    Ordering::Less => {
+                        if !self.advance() {
+                            return SkipResult::End;
+                        }
+                    }
+                    Ordering::Equal => {
+                        return SkipResult::Reached;
+                    }
+                    Ordering::Greater => {
+                        debug_assert!(self.doc() > target);
+                        return SkipResult::OverStep;
+                    }
+                }
+            },
+            Ordering::Less => {
+                debug_assert!(self.doc() > target);
+                SkipResult::OverStep
             }
-            doc
         }
     }
 
@@ -98,7 +122,7 @@ impl DocSet for BitSetDocSet {
 mod tests {
     use super::BitSetDocSet;
     use crate::common::BitSet;
-    use crate::docset::{DocSet, TERMINATED};
+    use crate::docset::{DocSet, SkipResult};
     use crate::DocId;
 
     fn create_docbitset(docs: &[DocId], max_doc: DocId) -> BitSetDocSet {
@@ -109,31 +133,19 @@ mod tests {
         BitSetDocSet::from(docset)
     }
 
-    #[test]
-    fn test_empty() {
-        let bitset = BitSet::with_max_value(1000);
-        let mut empty = BitSetDocSet::from(bitset);
-        assert_eq!(empty.advance(), TERMINATED)
-    }
-
-    #[test]
-    fn test_seek_terminated() {
-        let bitset = BitSet::with_max_value(1000);
-        let mut empty = BitSetDocSet::from(bitset);
-        assert_eq!(empty.seek(TERMINATED), TERMINATED)
-    }
-
     fn test_go_through_sequential(docs: &[DocId]) {
         let mut docset = create_docbitset(docs, 1_000u32);
         for &doc in docs {
+            assert!(docset.advance());
             assert_eq!(doc, docset.doc());
-            docset.advance();
         }
-        assert_eq!(docset.advance(), TERMINATED);
+        assert!(!docset.advance());
+        assert!(!docset.advance());
     }
 
     #[test]
     fn test_docbitset_sequential() {
+        test_go_through_sequential(&[]);
         test_go_through_sequential(&[1, 2, 3]);
         test_go_through_sequential(&[1, 2, 3, 4, 5, 63, 64, 65]);
         test_go_through_sequential(&[63, 64, 65]);
@@ -144,64 +156,64 @@ mod tests {
     fn test_docbitset_skip() {
         {
             let mut docset = create_docbitset(&[1, 5, 6, 7, 5112], 10_000);
-            assert_eq!(docset.seek(7), 7);
+            assert_eq!(docset.skip_next(7), SkipResult::Reached);
             assert_eq!(docset.doc(), 7);
-            assert_eq!(docset.advance(), 5112);
+            assert!(docset.advance(), 7);
             assert_eq!(docset.doc(), 5112);
-            assert_eq!(docset.advance(), TERMINATED);
+            assert!(!docset.advance());
         }
         {
             let mut docset = create_docbitset(&[1, 5, 6, 7, 5112], 10_000);
-            assert_eq!(docset.seek(3), 5);
+            assert_eq!(docset.skip_next(3), SkipResult::OverStep);
             assert_eq!(docset.doc(), 5);
-            assert_eq!(docset.advance(), 6);
+            assert!(docset.advance());
         }
         {
             let mut docset = create_docbitset(&[5112], 10_000);
-            assert_eq!(docset.seek(5112), 5112);
+            assert_eq!(docset.skip_next(5112), SkipResult::Reached);
             assert_eq!(docset.doc(), 5112);
-            assert_eq!(docset.advance(), TERMINATED);
+            assert!(!docset.advance());
         }
         {
             let mut docset = create_docbitset(&[5112], 10_000);
-            assert_eq!(docset.seek(5113), TERMINATED);
-            assert_eq!(docset.advance(), TERMINATED);
+            assert_eq!(docset.skip_next(5113), SkipResult::End);
+            assert!(!docset.advance());
         }
         {
             let mut docset = create_docbitset(&[5112], 10_000);
-            assert_eq!(docset.seek(5111), 5112);
+            assert_eq!(docset.skip_next(5111), SkipResult::OverStep);
             assert_eq!(docset.doc(), 5112);
-            assert_eq!(docset.advance(), TERMINATED);
+            assert!(!docset.advance());
         }
         {
             let mut docset = create_docbitset(&[1, 5, 6, 7, 5112, 5500, 6666], 10_000);
-            assert_eq!(docset.seek(5112), 5112);
+            assert_eq!(docset.skip_next(5112), SkipResult::Reached);
             assert_eq!(docset.doc(), 5112);
-            assert_eq!(docset.advance(), 5500);
+            assert!(docset.advance());
             assert_eq!(docset.doc(), 5500);
-            assert_eq!(docset.advance(), 6666);
+            assert!(docset.advance());
             assert_eq!(docset.doc(), 6666);
-            assert_eq!(docset.advance(), TERMINATED);
+            assert!(!docset.advance());
         }
         {
             let mut docset = create_docbitset(&[1, 5, 6, 7, 5112, 5500, 6666], 10_000);
-            assert_eq!(docset.seek(5111), 5112);
+            assert_eq!(docset.skip_next(5111), SkipResult::OverStep);
             assert_eq!(docset.doc(), 5112);
-            assert_eq!(docset.advance(), 5500);
+            assert!(docset.advance());
             assert_eq!(docset.doc(), 5500);
-            assert_eq!(docset.advance(), 6666);
+            assert!(docset.advance());
             assert_eq!(docset.doc(), 6666);
-            assert_eq!(docset.advance(), TERMINATED);
+            assert!(!docset.advance());
         }
         {
             let mut docset = create_docbitset(&[1, 5, 6, 7, 5112, 5513, 6666], 10_000);
-            assert_eq!(docset.seek(5111), 5112);
+            assert_eq!(docset.skip_next(5111), SkipResult::OverStep);
             assert_eq!(docset.doc(), 5112);
-            assert_eq!(docset.advance(), 5513);
+            assert!(docset.advance());
             assert_eq!(docset.doc(), 5513);
-            assert_eq!(docset.advance(), 6666);
+            assert!(docset.advance());
             assert_eq!(docset.doc(), 6666);
-            assert_eq!(docset.advance(), TERMINATED);
+            assert!(!docset.advance());
         }
     }
 }
@@ -211,7 +223,6 @@ mod bench {
 
     use super::BitSet;
     use super::BitSetDocSet;
-    use crate::docset::TERMINATED;
     use crate::test;
     use crate::tests;
     use crate::DocSet;
@@ -246,7 +257,7 @@ mod bench {
         }
         b.iter(|| {
             let mut docset = BitSetDocSet::from(bitset.clone());
-            while docset.advance() != TERMINATED {}
+            while docset.advance() {}
         });
     }
 }

src/query/bm25.rs

@@ -3,24 +3,21 @@ use crate::query::Explanation;
 use crate::Score;
 use crate::Searcher;
 use crate::Term;
-use serde::Deserialize;
-use serde::Serialize;
 
-const K1: Score = 1.2;
-const B: Score = 0.75;
+const K1: f32 = 1.2;
+const B: f32 = 0.75;
 
-fn idf(doc_freq: u64, doc_count: u64) -> Score {
-    assert!(doc_count >= doc_freq, "{} >= {}", doc_count, doc_freq);
-    let x = ((doc_count - doc_freq) as Score + 0.5) / (doc_freq as Score + 0.5);
-    (1.0 + x).ln()
+fn idf(doc_freq: u64, doc_count: u64) -> f32 {
+    let x = ((doc_count - doc_freq) as f32 + 0.5) / (doc_freq as f32 + 0.5);
+    (1f32 + x).ln()
 }
 
-fn cached_tf_component(fieldnorm: u32, average_fieldnorm: Score) -> Score {
-    K1 * (1.0 - B + B * fieldnorm as Score / average_fieldnorm)
+fn cached_tf_component(fieldnorm: u32, average_fieldnorm: f32) -> f32 {
+    K1 * (1f32 - B + B * fieldnorm as f32 / average_fieldnorm)
 }
 
-fn compute_tf_cache(average_fieldnorm: Score) -> [Score; 256] {
-    let mut cache: [Score; 256] = [0.0; 256];
+fn compute_tf_cache(average_fieldnorm: f32) -> [f32; 256] {
+    let mut cache = [0f32; 256];
     for (fieldnorm_id, cache_mut) in cache.iter_mut().enumerate() {
         let fieldnorm = FieldNormReader::id_to_fieldnorm(fieldnorm_id as u8);
         *cache_mut = cached_tf_component(fieldnorm, average_fieldnorm);
@@ -28,22 +25,15 @@ fn compute_tf_cache(average_fieldnorm: Score) -> [Score; 256] {
     cache
 }
 
-#[derive(Clone, PartialEq, Debug, Serialize, Deserialize)]
-pub struct BM25Params {
-    pub idf: Score,
-    pub avg_fieldnorm: Score,
-}
-
-#[derive(Clone)]
 pub struct BM25Weight {
     idf_explain: Explanation,
-    weight: Score,
-    cache: [Score; 256],
-    average_fieldnorm: Score,
+    weight: f32,
+    cache: [f32; 256],
+    average_fieldnorm: f32,
 }
 
 impl BM25Weight {
-    pub fn boost_by(&self, boost: Score) -> BM25Weight {
+    pub fn boost_by(&self, boost: f32) -> BM25Weight {
         BM25Weight {
             idf_explain: self.idf_explain.clone(),
             weight: self.weight * boost,
@@ -70,11 +60,19 @@ impl BM25Weight {
             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;
+        let average_fieldnorm = total_num_tokens as f32 / total_num_docs as f32;
 
+        let mut idf_explain: Explanation;
         if terms.len() == 1 {
             let term_doc_freq = searcher.doc_freq(&terms[0]);
-            BM25Weight::for_one_term(term_doc_freq, total_num_docs, average_fieldnorm)
+            let idf = idf(term_doc_freq, total_num_docs);
+            idf_explain =
+                Explanation::new("idf, computed as log(1 + (N - n + 0.5) / (n + 0.5))", idf);
+            idf_explain.add_const(
+                "n, number of docs containing this term",
+                term_doc_freq as f32,
+            );
+            idf_explain.add_const("N, total number of docs", total_num_docs as f32);
         } else {
             let idf = terms
                 .iter()
@@ -82,30 +80,14 @@ impl BM25Weight {
                     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)
+                .sum::<f32>();
+            idf_explain = Explanation::new("idf", idf);
         }
+        BM25Weight::new(idf_explain, average_fieldnorm)
     }
 
-    pub fn for_one_term(
-        term_doc_freq: u64,
-        total_num_docs: u64,
-        avg_fieldnorm: Score,
-    ) -> BM25Weight {
-        let idf = idf(term_doc_freq, total_num_docs);
-        let mut idf_explain =
-            Explanation::new("idf, computed as log(1 + (N - n + 0.5) / (n + 0.5))", idf);
-        idf_explain.add_const(
-            "n, number of docs containing this term",
-            term_doc_freq as Score,
-        );
-        idf_explain.add_const("N, total number of docs", total_num_docs as Score);
-        BM25Weight::new(idf_explain, avg_fieldnorm)
-    }
-
-    fn new(idf_explain: Explanation, average_fieldnorm: Score) -> BM25Weight {
-        let weight = idf_explain.value() * (1.0 + K1);
+    fn new(idf_explain: Explanation, average_fieldnorm: f32) -> BM25Weight {
+        let weight = idf_explain.value() * (1f32 + K1);
         BM25Weight {
             idf_explain,
             weight,
@@ -116,27 +98,19 @@ impl BM25Weight {
 
     #[inline(always)]
     pub fn score(&self, fieldnorm_id: u8, term_freq: u32) -> Score {
-        self.weight * self.tf_factor(fieldnorm_id, term_freq)
-    }
-
-    pub fn max_score(&self) -> Score {
-        self.score(255u8, 2_013_265_944)
-    }
-
-    #[inline(always)]
-    pub(crate) fn tf_factor(&self, fieldnorm_id: u8, term_freq: u32) -> Score {
-        let term_freq = term_freq as Score;
         let norm = self.cache[fieldnorm_id as usize];
-        term_freq / (term_freq + norm)
+        let term_freq = term_freq as f32;
+        self.weight * term_freq / (term_freq + norm)
     }
 
     pub fn explain(&self, fieldnorm_id: u8, term_freq: u32) -> Explanation {
         // The explain format is directly copied from Lucene's.
         // (So, Kudos to Lucene)
+
         let score = self.score(fieldnorm_id, term_freq);
 
         let norm = self.cache[fieldnorm_id as usize];
-        let term_freq = term_freq as Score;
+        let term_freq = term_freq as f32;
         let right_factor = term_freq / (term_freq + norm);
 
         let mut tf_explanation = Explanation::new(
@@ -149,12 +123,12 @@ impl BM25Weight {
         tf_explanation.add_const("b, length normalization parameter", B);
         tf_explanation.add_const(
             "dl, length of field",
-            FieldNormReader::id_to_fieldnorm(fieldnorm_id) as Score,
+            FieldNormReader::id_to_fieldnorm(fieldnorm_id) as f32,
         );
         tf_explanation.add_const("avgdl, average length of field", self.average_fieldnorm);
 
         let mut explanation = Explanation::new("TermQuery, product of...", score);
-        explanation.add_detail(Explanation::new("(K1+1)", K1 + 1.0));
+        explanation.add_detail(Explanation::new("(K1+1)", K1 + 1f32));
         explanation.add_detail(self.idf_explain.clone());
         explanation.add_detail(tf_explanation);
         explanation
@@ -165,11 +139,10 @@ impl BM25Weight {
 mod tests {
 
     use super::idf;
-    use crate::{assert_nearly_equals, Score};
+    use crate::tests::assert_nearly_equals;
 
     #[test]
     fn test_idf() {
-        let score: Score = 2.0;
-        assert_nearly_equals!(idf(1, 2), score.ln());
+        assert_nearly_equals(idf(1, 2), 0.6931472);
     }
 }

src/query/boolean_query/block_wand.rs

@@ -1,434 +0,0 @@
-use crate::query::term_query::TermScorer;
-use crate::query::Scorer;
-use crate::{DocId, DocSet, Score, TERMINATED};
-use std::ops::Deref;
-use std::ops::DerefMut;
-
-/// 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.
-/// - `before_pivot_len` number of term_scorers such that term_scorer.doc() < pivot.
-/// - `pivot_len` number of term_scorers such that term_scorer.doc() <= pivot.
-///
-/// We always have `before_pivot_len` < `pivot_len`.
-///
-/// None is returned if we establish that no document can exceed the threshold.
-fn find_pivot_doc(
-    term_scorers: &[TermScorerWithMaxScore],
-    threshold: Score,
-) -> Option<(usize, usize, DocId)> {
-    let mut max_score = 0.0;
-    let mut before_pivot_len = 0;
-    let mut pivot_doc = TERMINATED;
-    while before_pivot_len < term_scorers.len() {
-        let term_scorer = &term_scorers[before_pivot_len];
-        max_score += term_scorer.max_score;
-        if max_score > threshold {
-            pivot_doc = term_scorer.doc();
-            break;
-        }
-        before_pivot_len += 1;
-    }
-    if pivot_doc == TERMINATED {
-        return None;
-    }
-    // Right now i is an ordinal, we want a len.
-    let mut pivot_len = before_pivot_len + 1;
-    // Some other term_scorer may be positioned on the same document.
-    pivot_len += term_scorers[pivot_len..]
-        .iter()
-        .take_while(|term_scorer| term_scorer.doc() == pivot_doc)
-        .count();
-    Some((before_pivot_len, pivot_len, pivot_doc))
-}
-
-// 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() {
-        let scorer = &scorers[scorer_ord];
-        if scorer.last_doc_in_block() <= doc_to_seek_after {
-            doc_to_seek_after = scorer.last_doc_in_block();
-            scorer_to_seek = scorer_ord;
-        }
-    }
-    for scorer in &scorers[pivot_len..] {
-        if scorer.doc() <= doc_to_seek_after {
-            doc_to_seek_after = scorer.doc();
-        }
-    }
-    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
-// except term_scorers[ord] that might be in advance compared to its ranks,
-// bubble up term_scorers[ord] in order to restore the ordering.
-fn restore_ordering(term_scorers: &mut Vec<TermScorerWithMaxScore>, ord: usize) {
-    let doc = term_scorers[ord].doc();
-    for i in ord + 1..term_scorers.len() {
-        if term_scorers[i].doc() >= doc {
-            break;
-        }
-        term_scorers.swap(i, i - 1);
-    }
-    debug_assert!(is_sorted(term_scorers.iter().map(|scorer| scorer.doc())));
-}
-
-// Attempts to advance all term_scorers between `&term_scorers[0..before_len]` to the pivot.
-// If this works, return true.
-// If this fails (ie: one of the term_scorer does not contain `pivot_doc` and seek goes past the
-// pivot), reorder the term_scorers to ensure the list is still sorted and returns `false`.
-// If a term_scorer reach TERMINATED in the process return false remove the term_scorer and return.
-fn align_scorers(
-    term_scorers: &mut Vec<TermScorerWithMaxScore>,
-    pivot_doc: DocId,
-    before_pivot_len: usize,
-) -> bool {
-    debug_assert_ne!(pivot_doc, TERMINATED);
-    for i in (0..before_pivot_len).rev() {
-        let new_doc = term_scorers[i].seek(pivot_doc);
-        if new_doc != pivot_doc {
-            if new_doc == TERMINATED {
-                term_scorers.swap_remove(i);
-            }
-            // We went past the pivot.
-            // We just go through the outer loop mechanic (Note that pivot is
-            // still a possible candidate).
-            //
-            // Termination is still guaranteed since we can only consider the same
-            // pivot at most term_scorers.len() - 1 times.
-            restore_ordering(term_scorers, i);
-            return false;
-        }
-    }
-    true
-}
-
-// Assumes terms_scorers[..pivot_len] are positioned on the same doc (pivot_doc).
-// Advance term_scorers[..pivot_len] and out of these removes the terminated scores.
-// Restores the ordering of term_scorers.
-fn advance_all_scorers_on_pivot(term_scorers: &mut Vec<TermScorerWithMaxScore>, pivot_len: usize) {
-    for term_scorer in &mut term_scorers[..pivot_len] {
-        term_scorer.advance();
-    }
-    // TODO use drain_filter when available.
-    let mut i = 0;
-    while i != term_scorers.len() {
-        if term_scorers[i].doc() == TERMINATED {
-            term_scorers.swap_remove(i);
-        } else {
-            i += 1;
-        }
-    }
-    term_scorers.sort_by_key(|scorer| scorer.doc());
-}
-
-pub fn block_wand(
-    mut scorers: Vec<TermScorer>,
-    mut threshold: Score,
-    callback: &mut dyn FnMut(u32, Score) -> Score,
-) {
-    let mut scorers: Vec<TermScorerWithMaxScore> = scorers
-        .iter_mut()
-        .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)
-    {
-        debug_assert!(is_sorted(scorers.iter().map(|scorer| scorer.doc())));
-        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();
-
-        // 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.
-            //
-            // 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;
-            }
-            prev = doc;
-        }
-    }
-    true
-}
-#[cfg(test)]
-mod tests {
-    use crate::query::score_combiner::SumCombiner;
-    use crate::query::term_query::TermScorer;
-    use crate::query::Union;
-    use crate::query::{BM25Weight, Scorer};
-    use crate::{DocId, DocSet, Score, TERMINATED};
-    use proptest::prelude::*;
-    use std::cmp::Ordering;
-    use std::collections::BinaryHeap;
-    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)
-        }
-    }
-
-    fn nearly_equals(left: Score, right: Score) -> bool {
-        (left - right).abs() < 0.000001 * (left + right).abs()
-    }
-
-    fn compute_checkpoints_for_each_pruning(
-        term_scorers: Vec<TermScorer>,
-        n: usize,
-    ) -> Vec<(DocId, Score)> {
-        let mut heap: BinaryHeap<Float> = BinaryHeap::with_capacity(n);
-        let mut checkpoints: Vec<(DocId, Score)> = Vec::new();
-        let mut limit: Score = 0.0;
-        super::block_wand(term_scorers, Score::MIN, &mut |doc, score| {
-            heap.push(Float(score));
-            if heap.len() > n {
-                heap.pop().unwrap();
-            }
-            if heap.len() == n {
-                limit = heap.peek().unwrap().0;
-            }
-            if !nearly_equals(score, limit) {
-                checkpoints.push((doc, score));
-            }
-            return limit;
-        });
-        checkpoints
-    }
-
-    fn compute_checkpoints_manual(term_scorers: Vec<TermScorer>, n: usize) -> Vec<(DocId, Score)> {
-        let mut heap: BinaryHeap<Float> = BinaryHeap::with_capacity(n);
-        let mut checkpoints: Vec<(DocId, Score)> = Vec::new();
-        let mut scorer: Union<TermScorer, SumCombiner> = Union::from(term_scorers);
-
-        let mut limit = Score::MIN;
-        loop {
-            if scorer.doc() == TERMINATED {
-                break;
-            }
-            let doc = scorer.doc();
-            let score = scorer.score();
-            if score > limit {
-                heap.push(Float(score));
-                if heap.len() > n {
-                    heap.pop().unwrap();
-                }
-                if heap.len() == n {
-                    limit = heap.peek().unwrap().0;
-                }
-                if !nearly_equals(score, limit) {
-                    checkpoints.push((doc, score));
-                }
-            }
-            scorer.advance();
-        }
-        checkpoints
-    }
-
-    const MAX_TERM_FREQ: u32 = 100u32;
-
-    fn posting_list(max_doc: u32) -> BoxedStrategy<Vec<(DocId, u32)>> {
-        (1..max_doc + 1)
-            .prop_flat_map(move |doc_freq| {
-                (
-                    proptest::bits::bitset::sampled(doc_freq as usize, 0..max_doc as usize),
-                    proptest::collection::vec(1u32..MAX_TERM_FREQ, doc_freq as usize),
-                )
-            })
-            .prop_map(|(docset, term_freqs)| {
-                docset
-                    .iter()
-                    .map(|doc| doc as u32)
-                    .zip(term_freqs.iter().cloned())
-                    .collect::<Vec<_>>()
-            })
-            .boxed()
-    }
-
-    fn gen_term_scorers(num_scorers: usize) -> BoxedStrategy<(Vec<Vec<(DocId, u32)>>, Vec<u32>)> {
-        (1u32..100u32)
-            .prop_flat_map(move |max_doc: u32| {
-                (
-                    proptest::collection::vec(posting_list(max_doc), num_scorers),
-                    proptest::collection::vec(2u32..10u32 * MAX_TERM_FREQ, max_doc as usize),
-                )
-            })
-            .boxed()
-    }
-
-    fn test_block_wand_aux(posting_lists: &[Vec<(DocId, u32)>], fieldnorms: &[u32]) {
-        // We virtually repeat all docs 64 times in order to emulate blocks of 2 documents
-        // and surface blogs more easily.
-        const REPEAT: usize = 64;
-        let fieldnorms_expanded = fieldnorms
-            .iter()
-            .cloned()
-            .flat_map(|fieldnorm| iter::repeat(fieldnorm).take(REPEAT))
-            .collect::<Vec<u32>>();
-
-        let postings_lists_expanded: Vec<Vec<(DocId, u32)>> = posting_lists
-            .iter()
-            .map(|posting_list| {
-                posting_list
-                    .into_iter()
-                    .cloned()
-                    .flat_map(|(doc, term_freq)| {
-                        (0 as u32..REPEAT as u32).map(move |offset| {
-                            (
-                                doc * (REPEAT as u32) + offset,
-                                if offset == 0 { term_freq } else { 1 },
-                            )
-                        })
-                    })
-                    .collect::<Vec<(DocId, u32)>>()
-            })
-            .collect::<Vec<_>>();
-
-        let total_fieldnorms: u64 = fieldnorms_expanded
-            .iter()
-            .cloned()
-            .map(|fieldnorm| fieldnorm as u64)
-            .sum();
-        let average_fieldnorm = (total_fieldnorms as Score) / (fieldnorms_expanded.len() as Score);
-        let max_doc = fieldnorms_expanded.len();
-
-        let term_scorers: Vec<TermScorer> = postings_lists_expanded
-            .iter()
-            .map(|postings| {
-                let bm25_weight = BM25Weight::for_one_term(
-                    postings.len() as u64,
-                    max_doc as u64,
-                    average_fieldnorm,
-                );
-                TermScorer::create_for_test(postings, &fieldnorms_expanded[..], bm25_weight)
-            })
-            .collect();
-        for top_k in 1..4 {
-            let checkpoints_for_each_pruning =
-                compute_checkpoints_for_each_pruning(term_scorers.clone(), top_k);
-            let checkpoints_manual = compute_checkpoints_manual(term_scorers.clone(), top_k);
-            assert_eq!(checkpoints_for_each_pruning.len(), checkpoints_manual.len());
-            for (&(left_doc, left_score), &(right_doc, right_score)) in checkpoints_for_each_pruning
-                .iter()
-                .zip(checkpoints_manual.iter())
-            {
-                assert_eq!(left_doc, right_doc);
-                assert!(nearly_equals(left_score, right_score));
-            }
-        }
-    }
-
-    proptest! {
-        #![proptest_config(ProptestConfig::with_cases(500))]
-        #[test]
-        fn test_block_wand_two_term_scorers((posting_lists, fieldnorms) in gen_term_scorers(2)) {
-            test_block_wand_aux(&posting_lists[..], &fieldnorms[..]);
-        }
-    }
-
-    proptest! {
-        #![proptest_config(ProptestConfig::with_cases(500))]
-        #[test]
-        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_weight.rs

@@ -1,9 +1,7 @@
 use crate::core::SegmentReader;
-use crate::postings::FreqReadingOption;
 use crate::query::explanation::does_not_match;
 use crate::query::score_combiner::{DoNothingCombiner, ScoreCombiner, SumWithCoordsCombiner};
 use crate::query::term_query::TermScorer;
-use crate::query::weight::{for_each_pruning_scorer, for_each_scorer};
 use crate::query::EmptyScorer;
 use crate::query::Exclude;
 use crate::query::Occur;
@@ -12,21 +10,16 @@ use crate::query::Scorer;
 use crate::query::Union;
 use crate::query::Weight;
 use crate::query::{intersect_scorers, Explanation};
-use crate::{DocId, Score};
+use crate::{DocId, SkipResult};
 use std::collections::HashMap;
 
-enum SpecializedScorer {
-    TermUnion(Vec<TermScorer>),
-    Other(Box<dyn Scorer>),
-}
-
-fn scorer_union<TScoreCombiner>(scorers: Vec<Box<dyn Scorer>>) -> SpecializedScorer
+fn scorer_union<TScoreCombiner>(scorers: Vec<Box<dyn Scorer>>) -> Box<dyn Scorer>
 where
     TScoreCombiner: ScoreCombiner,
 {
     assert!(!scorers.is_empty());
     if scorers.len() == 1 {
-        return SpecializedScorer::Other(scorers.into_iter().next().unwrap()); //< we checked the size beforehands
+        return scorers.into_iter().next().unwrap(); //< we checked the size beforehands
     }
 
     {
@@ -36,30 +29,14 @@ where
                 .into_iter()
                 .map(|scorer| *(scorer.downcast::<TermScorer>().map_err(|_| ()).unwrap()))
                 .collect();
-            if scorers
-                .iter()
-                .all(|scorer| scorer.freq_reading_option() == FreqReadingOption::ReadFreq)
-            {
-                // Block wand is only available iff we read frequencies.
-                return SpecializedScorer::TermUnion(scorers);
-            } else {
-                return SpecializedScorer::Other(Box::new(Union::<_, TScoreCombiner>::from(
-                    scorers,
-                )));
-            }
+            let scorer: Box<dyn Scorer> =
+                Box::new(Union::<TermScorer, TScoreCombiner>::from(scorers));
+            return scorer;
         }
     }
-    SpecializedScorer::Other(Box::new(Union::<_, TScoreCombiner>::from(scorers)))
-}
 
-fn into_box_scorer<TScoreCombiner: ScoreCombiner>(scorer: SpecializedScorer) -> Box<dyn Scorer> {
-    match scorer {
-        SpecializedScorer::TermUnion(term_scorers) => {
-            let union_scorer = Union::<TermScorer, TScoreCombiner>::from(term_scorers);
-            Box::new(union_scorer)
-        }
-        SpecializedScorer::Other(scorer) => scorer,
-    }
+    let scorer: Box<dyn Scorer> = Box::new(Union::<_, TScoreCombiner>::from(scorers));
+    scorer
 }
 
 pub struct BooleanWeight {
@@ -78,7 +55,7 @@ impl BooleanWeight {
     fn per_occur_scorers(
         &self,
         reader: &SegmentReader,
-        boost: Score,
+        boost: f32,
     ) -> crate::Result<HashMap<Occur, Vec<Box<dyn Scorer>>>> {
         let mut per_occur_scorers: HashMap<Occur, Vec<Box<dyn Scorer>>> = HashMap::new();
         for &(ref occur, ref subweight) in &self.weights {
@@ -94,52 +71,42 @@ impl BooleanWeight {
     fn complex_scorer<TScoreCombiner: ScoreCombiner>(
         &self,
         reader: &SegmentReader,
-        boost: Score,
-    ) -> crate::Result<SpecializedScorer> {
+        boost: f32,
+    ) -> crate::Result<Box<dyn Scorer>> {
         let mut per_occur_scorers = self.per_occur_scorers(reader, boost)?;
 
-        let should_scorer_opt: Option<SpecializedScorer> = per_occur_scorers
+        let should_scorer_opt: Option<Box<dyn Scorer>> = per_occur_scorers
             .remove(&Occur::Should)
             .map(scorer_union::<TScoreCombiner>);
 
         let exclude_scorer_opt: Option<Box<dyn Scorer>> = per_occur_scorers
             .remove(&Occur::MustNot)
-            .map(scorer_union::<DoNothingCombiner>)
-            .map(into_box_scorer::<DoNothingCombiner>);
+            .map(scorer_union::<TScoreCombiner>);
 
         let must_scorer_opt: Option<Box<dyn Scorer>> = per_occur_scorers
             .remove(&Occur::Must)
             .map(intersect_scorers);
 
-        let positive_scorer: SpecializedScorer = match (should_scorer_opt, must_scorer_opt) {
+        let positive_scorer: Box<dyn Scorer> = match (should_scorer_opt, must_scorer_opt) {
             (Some(should_scorer), Some(must_scorer)) => {
                 if self.scoring_enabled {
-                    SpecializedScorer::Other(Box::new(RequiredOptionalScorer::<
-                        Box<dyn Scorer>,
-                        Box<dyn Scorer>,
-                        TScoreCombiner,
-                    >::new(
+                    Box::new(RequiredOptionalScorer::<_, _, TScoreCombiner>::new(
                         must_scorer,
-                        into_box_scorer::<TScoreCombiner>(should_scorer),
-                    )))
+                        should_scorer,
+                    ))
                 } else {
-                    SpecializedScorer::Other(must_scorer)
+                    must_scorer
                 }
             }
-            (None, Some(must_scorer)) => SpecializedScorer::Other(must_scorer),
+            (None, Some(must_scorer)) => must_scorer,
             (Some(should_scorer), None) => should_scorer,
             (None, None) => {
-                return Ok(SpecializedScorer::Other(Box::new(EmptyScorer)));
+                return Ok(Box::new(EmptyScorer));
             }
         };
 
         if let Some(exclude_scorer) = exclude_scorer_opt {
-            let positive_scorer_boxed: Box<dyn Scorer> =
-                into_box_scorer::<TScoreCombiner>(positive_scorer);
-            Ok(SpecializedScorer::Other(Box::new(Exclude::new(
-                positive_scorer_boxed,
-                exclude_scorer,
-            ))))
+            Ok(Box::new(Exclude::new(positive_scorer, exclude_scorer)))
         } else {
             Ok(positive_scorer)
         }
@@ -147,7 +114,7 @@ impl BooleanWeight {
 }
 
 impl Weight for BooleanWeight {
-    fn scorer(&self, reader: &SegmentReader, boost: Score) -> crate::Result<Box<dyn Scorer>> {
+    fn scorer(&self, reader: &SegmentReader, boost: f32) -> crate::Result<Box<dyn Scorer>> {
         if self.weights.is_empty() {
             Ok(Box::new(EmptyScorer))
         } else if self.weights.len() == 1 {
@@ -159,22 +126,18 @@ impl Weight for BooleanWeight {
             }
         } else if self.scoring_enabled {
             self.complex_scorer::<SumWithCoordsCombiner>(reader, boost)
-                .map(|specialized_scorer| {
-                    into_box_scorer::<SumWithCoordsCombiner>(specialized_scorer)
-                })
         } else {
             self.complex_scorer::<DoNothingCombiner>(reader, boost)
-                .map(into_box_scorer::<DoNothingCombiner>)
         }
     }
 
     fn explain(&self, reader: &SegmentReader, doc: DocId) -> crate::Result<Explanation> {
-        let mut scorer = self.scorer(reader, 1.0)?;
-        if scorer.seek(doc) != doc {
+        let mut scorer = self.scorer(reader, 1.0f32)?;
+        if scorer.skip_next(doc) != SkipResult::Reached {
             return Err(does_not_match(doc));
         }
         if !self.scoring_enabled {
-            return Ok(Explanation::new("BooleanQuery with no scoring", 1.0));
+            return Ok(Explanation::new("BooleanQuery with no scoring", 1f32));
         }
 
         let mut explanation = Explanation::new("BooleanClause. Sum of ...", scorer.score());
@@ -187,53 +150,6 @@ impl Weight for BooleanWeight {
         }
         Ok(explanation)
     }
-
-    fn for_each(
-        &self,
-        reader: &SegmentReader,
-        callback: &mut dyn FnMut(DocId, Score),
-    ) -> crate::Result<()> {
-        let scorer = self.complex_scorer::<SumWithCoordsCombiner>(reader, 1.0)?;
-        match scorer {
-            SpecializedScorer::TermUnion(term_scorers) => {
-                let mut union_scorer =
-                    Union::<TermScorer, SumWithCoordsCombiner>::from(term_scorers);
-                for_each_scorer(&mut union_scorer, callback);
-            }
-            SpecializedScorer::Other(mut scorer) => {
-                for_each_scorer(scorer.as_mut(), callback);
-            }
-        }
-        Ok(())
-    }
-
-    /// Calls `callback` with all of the `(doc, score)` for which score
-    /// is exceeding a given threshold.
-    ///
-    /// This method is useful for the TopDocs collector.
-    /// For all docsets, the blanket implementation has the benefit
-    /// of prefiltering (doc, score) pairs, avoiding the
-    /// virtual dispatch cost.
-    ///
-    /// More importantly, it makes it possible for scorers to implement
-    /// important optimization (e.g. BlockWAND for union).
-    fn for_each_pruning(
-        &self,
-        threshold: Score,
-        reader: &SegmentReader,
-        callback: &mut dyn FnMut(DocId, Score) -> Score,
-    ) -> crate::Result<()> {
-        let scorer = self.complex_scorer::<SumWithCoordsCombiner>(reader, 1.0)?;
-        match scorer {
-            SpecializedScorer::TermUnion(term_scorers) => {
-                super::block_wand(term_scorers, threshold, callback);
-            }
-            SpecializedScorer::Other(mut scorer) => {
-                for_each_pruning_scorer(scorer.as_mut(), threshold, callback);
-            }
-        }
-        Ok(())
-    }
 }
 
 fn is_positive_occur(occur: Occur) -> bool {

src/query/boolean_query/mod.rs

@@ -1,17 +1,13 @@
-mod block_wand;
 mod boolean_query;
 mod boolean_weight;
 
-pub(crate) use self::block_wand::block_wand;
 pub use self::boolean_query::BooleanQuery;
 
 #[cfg(test)]
 mod tests {
 
     use super::*;
-    use crate::assert_nearly_equals;
     use crate::collector::tests::TEST_COLLECTOR_WITH_SCORE;
-    use crate::collector::TopDocs;
     use crate::query::score_combiner::SumWithCoordsCombiner;
     use crate::query::term_query::TermScorer;
     use crate::query::Intersection;
@@ -22,8 +18,9 @@ mod tests {
     use crate::query::Scorer;
     use crate::query::TermQuery;
     use crate::schema::*;
+    use crate::tests::assert_nearly_equals;
     use crate::Index;
-    use crate::{DocAddress, DocId, Score};
+    use crate::{DocAddress, DocId};
 
     fn aux_test_helper() -> (Index, Field) {
         let mut schema_builder = Schema::builder();
@@ -32,13 +29,26 @@ 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.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 doc = doc!(text_field => "a b c");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "a c");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "b c");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "a b c d");
+                index_writer.add_document(doc);
+            }
+            {
+                let doc = doc!(text_field => "d");
+                index_writer.add_document(doc);
             }
             assert!(index_writer.commit().is_ok());
         }
@@ -61,7 +71,9 @@ mod tests {
         let query = query_parser.parse_query("+a").unwrap();
         let searcher = index.reader().unwrap().searcher();
         let weight = query.weight(&searcher, true).unwrap();
-        let scorer = weight.scorer(searcher.segment_reader(0u32), 1.0).unwrap();
+        let scorer = weight
+            .scorer(searcher.segment_reader(0u32), 1.0f32)
+            .unwrap();
         assert!(scorer.is::<TermScorer>());
     }
 
@@ -73,13 +85,17 @@ mod tests {
         {
             let query = query_parser.parse_query("+a +b +c").unwrap();
             let weight = query.weight(&searcher, true).unwrap();
-            let scorer = weight.scorer(searcher.segment_reader(0u32), 1.0).unwrap();
+            let scorer = weight
+                .scorer(searcher.segment_reader(0u32), 1.0f32)
+                .unwrap();
             assert!(scorer.is::<Intersection<TermScorer>>());
         }
         {
             let query = query_parser.parse_query("+a +(b c)").unwrap();
             let weight = query.weight(&searcher, true).unwrap();
-            let scorer = weight.scorer(searcher.segment_reader(0u32), 1.0).unwrap();
+            let scorer = weight
+                .scorer(searcher.segment_reader(0u32), 1.0f32)
+                .unwrap();
             assert!(scorer.is::<Intersection<Box<dyn Scorer>>>());
         }
     }
@@ -92,7 +108,9 @@ mod tests {
         {
             let query = query_parser.parse_query("+a b").unwrap();
             let weight = query.weight(&searcher, true).unwrap();
-            let scorer = weight.scorer(searcher.segment_reader(0u32), 1.0).unwrap();
+            let scorer = weight
+                .scorer(searcher.segment_reader(0u32), 1.0f32)
+                .unwrap();
             assert!(scorer.is::<RequiredOptionalScorer<
                 Box<dyn Scorer>,
                 Box<dyn Scorer>,
@@ -102,7 +120,9 @@ mod tests {
         {
             let query = query_parser.parse_query("+a b").unwrap();
             let weight = query.weight(&searcher, false).unwrap();
-            let scorer = weight.scorer(searcher.segment_reader(0u32), 1.0).unwrap();
+            let scorer = weight
+                .scorer(searcher.segment_reader(0u32), 1.0f32)
+                .unwrap();
             assert!(scorer.is::<TermScorer>());
         }
     }
@@ -133,6 +153,7 @@ mod tests {
                 .map(|doc| doc.1)
                 .collect::<Vec<DocId>>()
         };
+
         {
             let boolean_query = BooleanQuery::from(vec![(Occur::Must, make_term_query("a"))]);
             assert_eq!(matching_docs(&boolean_query), vec![0, 1, 3]);
@@ -169,54 +190,6 @@ mod tests {
         }
     }
 
-    #[test]
-    pub fn test_boolean_query_two_excluded() {
-        let (index, text_field) = aux_test_helper();
-
-        let make_term_query = |text: &str| {
-            let term_query = TermQuery::new(
-                Term::from_field_text(text_field, text),
-                IndexRecordOption::Basic,
-            );
-            let query: Box<dyn Query> = Box::new(term_query);
-            query
-        };
-
-        let reader = index.reader().unwrap();
-
-        let matching_topdocs = |query: &dyn Query| {
-            reader
-                .searcher()
-                .search(query, &TopDocs::with_limit(3))
-                .unwrap()
-        };
-
-        let score_doc_4: Score; // score of doc 4 should not be influenced by exclusion
-        {
-            let boolean_query_no_excluded =
-                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];
-            assert_eq!(top_doc, DocAddress(0, 4));
-            assert_eq!(topdocs_no_excluded[1].1, DocAddress(0, 3)); // ignore score of doc 3.
-            score_doc_4 = top_score;
-        }
-
-        {
-            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")),
-            ]);
-            let topdocs_excluded = matching_topdocs(&boolean_query_two_excluded);
-            assert_eq!(topdocs_excluded.len(), 1);
-            let (top_score, top_doc) = topdocs_excluded[0];
-            assert_eq!(top_doc, DocAddress(0, 4));
-            assert_eq!(top_score, score_doc_4);
-        }
-    }
-
     #[test]
     pub fn test_boolean_query_with_weight() {
         let mut schema_builder = Schema::builder();
@@ -224,7 +197,7 @@ 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"));
@@ -245,17 +218,19 @@ mod tests {
         let boolean_weight = boolean_query.weight(&searcher, true).unwrap();
         {
             let mut boolean_scorer = boolean_weight
-                .scorer(searcher.segment_reader(0u32), 1.0)
+                .scorer(searcher.segment_reader(0u32), 1.0f32)
                 .unwrap();
+            assert!(boolean_scorer.advance());
             assert_eq!(boolean_scorer.doc(), 0u32);
-            assert_nearly_equals!(boolean_scorer.score(), 0.84163445);
+            assert_nearly_equals(boolean_scorer.score(), 0.84163445f32);
         }
         {
             let mut boolean_scorer = boolean_weight
-                .scorer(searcher.segment_reader(0u32), 2.0)
+                .scorer(searcher.segment_reader(0u32), 2.0f32)
                 .unwrap();
+            assert!(boolean_scorer.advance());
             assert_eq!(boolean_scorer.doc(), 0u32);
-            assert_nearly_equals!(boolean_scorer.score(), 1.6832689);
+            assert_nearly_equals(boolean_scorer.score(), 1.6832689f32);
         }
     }
 
@@ -285,9 +260,170 @@ mod tests {
                 (Occur::Must, make_term_query("a")),
                 (Occur::Must, make_term_query("b")),
             ]);
-            let scores = score_docs(&boolean_query);
-            assert_nearly_equals!(scores[0], 0.977973);
-            assert_nearly_equals!(scores[1], 0.84699446);
+            assert_eq!(score_docs(&boolean_query), vec![0.977973, 0.84699446]);
         }
     }
+
+    // motivated by #554
+    #[test]
+    fn test_bm25_several_fields() {
+        let mut schema_builder = Schema::builder();
+        let title = schema_builder.add_text_field("title", TEXT);
+        let text = 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_with_num_threads(1, 3_000_000).unwrap();
+        index_writer.add_document(doc!(
+            // tf = 1 0
+            title =>  "Законы притяжения   Оксана Кулакова",
+            // tf = 1 0
+            text => "Законы притяжения Оксана Кулакова]  \n\nТема: Сексуальное искусство, Женственность\nТип товара: Запись вебинара (аудио)\nПродолжительность: 1,5 часа\n\nСсылка на вебинар:\n  ",
+        ));
+        index_writer.add_document(doc!(
+            // tf = 1 0
+            title => "Любимые русские пироги (Оксана Путан)",
+            // tf = 2 0
+            text => "http://i95.fastpic.ru/big/2017/0628/9a/615b9c8504d94a3893d7f496ac53539a.jpg \n\nОт издателя\nОксана Путан   профессиональный повар, автор кулинарных книг и известный кулинарный блогер. Ее рецепты отличаются практичностью, доступностью и пользуются огромной популярностью в русскоязычном интернете. Это третья книга автора о самом вкусном и ароматном   настоящих русских пирогах и выпечке!\nДаже новички на кухне легко готовят по ее рецептам. Оксана описывает процесс приготовления настолько подробно и понятно, что вам остается только наслаждаться готовкой и не тратить время на лишние усилия. Готовьте легко и просто!\n\nhttps://www.ozon.ru/context/detail/id/139872462/"
+        ));
+        index_writer.add_document(doc!(
+            // tf = 1 1
+            title =>  "PDF Мастер Класс \"Морячок\" (Оксана Лифенко)",
+            // tf = 0 0 
+            text => "https://i.ibb.co/pzvHrDN/I3d U T6 Gg TM.jpg\nhttps://i.ibb.co/NFrb6v6/N0ls Z9nwjb U.jpg\nВ описание входит штаны, кофта, берет, матросский воротник. Описание продается в формате PDF, состоит из 12 страниц формата А4 и может быть напечатано на любом принтере.\nОписание предназначено для кукол BJD RealPuki от FairyLand, но может подойти и другим подобным куклам. Также вы можете вязать этот наряд из обычной пряжи, и он подойдет для куколок побольше.\nhttps://vk.com/market 95724412?w=product 95724412_2212"
+        ));
+        for _ in 0..1_000 {
+            index_writer.add_document(doc!(
+                title =>  "a b d e f g",
+                text => "maitre corbeau sur un arbre perche tenait dans son bec un fromage Maitre rnard par lodeur alleche lui tint a peu pres ce langage."
+            ));
+        }
+        index_writer.commit().unwrap();
+        let reader = index.reader().unwrap();
+        let searcher = reader.searcher();
+        let query_parser = QueryParser::for_index(&index, vec![title, text]);
+        let query = query_parser.parse_query("Оксана Лифенко").unwrap();
+        let weight = query.weight(&searcher, true).unwrap();
+        let mut scorer = weight
+            .scorer(searcher.segment_reader(0u32), 1.0f32)
+            .unwrap();
+        scorer.advance();
+
+        let explanation = query.explain(&searcher, DocAddress(0u32, 0u32)).unwrap();
+        assert_eq!(
+            explanation.to_pretty_json(),
+            r#"{
+  "value": 12.997711,
+  "description": "BooleanClause. Sum of ...",
+  "details": [
+    {
+      "value": 12.997711,
+      "description": "BooleanClause. Sum of ...",
+      "details": [
+        {
+          "value": 6.551476,
+          "description": "TermQuery, product of...",
+          "details": [
+            {
+              "value": 2.2,
+              "description": "(K1+1)"
+            },
+            {
+              "value": 5.658984,
+              "description": "idf, computed as log(1 + (N - n + 0.5) / (n + 0.5))",
+              "details": [
+                {
+                  "value": 3.0,
+                  "description": "n, number of docs containing this term"
+                },
+                {
+                  "value": 1003.0,
+                  "description": "N, total number of docs"
+                }
+              ]
+            },
+            {
+              "value": 0.5262329,
+              "description": "freq / (freq + k1 * (1 - b + b * dl / avgdl))",
+              "details": [
+                {
+                  "value": 1.0,
+                  "description": "freq, occurrences of term within document"
+                },
+                {
+                  "value": 1.2,
+                  "description": "k1, term saturation parameter"
+                },
+                {
+                  "value": 0.75,
+                  "description": "b, length normalization parameter"
+                },
+                {
+                  "value": 4.0,
+                  "description": "dl, length of field"
+                },
+                {
+                  "value": 5.997009,
+                  "description": "avgdl, average length of field"
+                }
+              ]
+            }
+          ]
+        },
+        {
+          "value": 6.446235,
+          "description": "TermQuery, product of...",
+          "details": [
+            {
+              "value": 2.2,
+              "description": "(K1+1)"
+            },
+            {
+              "value": 5.9954567,
+              "description": "idf, computed as log(1 + (N - n + 0.5) / (n + 0.5))",
+              "details": [
+                {
+                  "value": 2.0,
+                  "description": "n, number of docs containing this term"
+                },
+                {
+                  "value": 1003.0,
+                  "description": "N, total number of docs"
+                }
+              ]
+            },
+            {
+              "value": 0.4887212,
+              "description": "freq / (freq + k1 * (1 - b + b * dl / avgdl))",
+              "details": [
+                {
+                  "value": 1.0,
+                  "description": "freq, occurrences of term within document"
+                },
+                {
+                  "value": 1.2,
+                  "description": "k1, term saturation parameter"
+                },
+                {
+                  "value": 0.75,
+                  "description": "b, length normalization parameter"
+                },
+                {
+                  "value": 20.0,
+                  "description": "dl, length of field"
+                },
+                {
+                  "value": 24.123629,
+                  "description": "avgdl, average length of field"
+                }
+              ]
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}"#
+        );
+    }
 }

src/query/boost_query.rs

@@ -1,7 +1,8 @@
+use crate::common::BitSet;
 use crate::fastfield::DeleteBitSet;
 use crate::query::explanation::does_not_match;
 use crate::query::{Explanation, Query, Scorer, Weight};
-use crate::{DocId, DocSet, Score, Searcher, SegmentReader, Term};
+use crate::{DocId, DocSet, Searcher, SegmentReader, SkipResult, Term};
 use std::collections::BTreeSet;
 use std::fmt;
 
@@ -12,12 +13,12 @@ use std::fmt;
 /// factor.
 pub struct BoostQuery {
     query: Box<dyn Query>,
-    boost: Score,
+    boost: f32,
 }
 
 impl BoostQuery {
     /// Builds a boost query.
-    pub fn new(query: Box<dyn Query>, boost: Score) -> BoostQuery {
+    pub fn new(query: Box<dyn Query>, boost: f32) -> BoostQuery {
         BoostQuery { query, boost }
     }
 }
@@ -55,23 +56,23 @@ impl Query for BoostQuery {
 
 pub(crate) struct BoostWeight {
     weight: Box<dyn Weight>,
-    boost: Score,
+    boost: f32,
 }
 
 impl BoostWeight {
-    pub fn new(weight: Box<dyn Weight>, boost: Score) -> Self {
+    pub fn new(weight: Box<dyn Weight>, boost: f32) -> Self {
         BoostWeight { weight, boost }
     }
 }
 
 impl Weight for BoostWeight {
-    fn scorer(&self, reader: &SegmentReader, boost: Score) -> crate::Result<Box<dyn Scorer>> {
+    fn scorer(&self, reader: &SegmentReader, boost: f32) -> crate::Result<Box<dyn Scorer>> {
         self.weight.scorer(reader, boost * self.boost)
     }
 
     fn explain(&self, reader: &SegmentReader, doc: u32) -> crate::Result<Explanation> {
-        let mut scorer = self.scorer(reader, 1.0)?;
-        if scorer.seek(doc) != doc {
+        let mut scorer = self.scorer(reader, 1.0f32)?;
+        if scorer.skip_next(doc) != SkipResult::Reached {
             return Err(does_not_match(doc));
         }
         let mut explanation =
@@ -88,22 +89,22 @@ impl Weight for BoostWeight {
 
 pub(crate) struct BoostScorer<S: Scorer> {
     underlying: S,
-    boost: Score,
+    boost: f32,
 }
 
 impl<S: Scorer> BoostScorer<S> {
-    pub fn new(underlying: S, boost: Score) -> BoostScorer<S> {
+    pub fn new(underlying: S, boost: f32) -> BoostScorer<S> {
         BoostScorer { underlying, boost }
     }
 }
 
 impl<S: Scorer> DocSet for BoostScorer<S> {
-    fn advance(&mut self) -> DocId {
+    fn advance(&mut self) -> bool {
         self.underlying.advance()
     }
 
-    fn seek(&mut self, target: DocId) -> DocId {
-        self.underlying.seek(target)
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
+        self.underlying.skip_next(target)
     }
 
     fn fill_buffer(&mut self, buffer: &mut [DocId]) -> usize {
@@ -118,6 +119,10 @@ impl<S: Scorer> DocSet for BoostScorer<S> {
         self.underlying.size_hint()
     }
 
+    fn append_to_bitset(&mut self, bitset: &mut BitSet) {
+        self.underlying.append_to_bitset(bitset)
+    }
+
     fn count(&mut self, delete_bitset: &DeleteBitSet) -> u32 {
         self.underlying.count(delete_bitset)
     }
@@ -128,7 +133,7 @@ impl<S: Scorer> DocSet for BoostScorer<S> {
 }
 
 impl<S: Scorer> Scorer for BoostScorer<S> {
-    fn score(&mut self) -> Score {
+    fn score(&mut self) -> f32 {
         self.underlying.score() * self.boost
     }
 }
@@ -144,7 +149,7 @@ 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();

src/query/empty_query.rs

@@ -1,5 +1,4 @@
 use super::Scorer;
-use crate::docset::TERMINATED;
 use crate::query::explanation::does_not_match;
 use crate::query::Weight;
 use crate::query::{Explanation, Query};
@@ -34,7 +33,7 @@ impl Query for EmptyQuery {
 /// It is useful for tests and handling edge cases.
 pub struct EmptyWeight;
 impl Weight for EmptyWeight {
-    fn scorer(&self, _reader: &SegmentReader, _boost: Score) -> crate::Result<Box<dyn Scorer>> {
+    fn scorer(&self, _reader: &SegmentReader, _boost: f32) -> crate::Result<Box<dyn Scorer>> {
         Ok(Box::new(EmptyScorer))
     }
 
@@ -49,12 +48,15 @@ impl Weight for EmptyWeight {
 pub struct EmptyScorer;
 
 impl DocSet for EmptyScorer {
-    fn advance(&mut self) -> DocId {
-        TERMINATED
+    fn advance(&mut self) -> bool {
+        false
     }
 
     fn doc(&self) -> DocId {
-        TERMINATED
+        panic!(
+            "You may not call .doc() on a scorer \
+             where the last call to advance() did not return true."
+        );
     }
 
     fn size_hint(&self) -> u32 {
@@ -64,21 +66,24 @@ impl DocSet for EmptyScorer {
 
 impl Scorer for EmptyScorer {
     fn score(&mut self) -> Score {
-        0.0
+        0f32
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::docset::TERMINATED;
     use crate::query::EmptyScorer;
     use crate::DocSet;
 
     #[test]
     fn test_empty_scorer() {
         let mut empty_scorer = EmptyScorer;
-        assert_eq!(empty_scorer.doc(), TERMINATED);
-        assert_eq!(empty_scorer.advance(), TERMINATED);
-        assert_eq!(empty_scorer.doc(), TERMINATED);
+        assert!(!empty_scorer.advance());
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_empty_scorer_panic_on_doc_call() {
+        EmptyScorer.doc();
     }
 }

src/query/exclude.rs

@@ -1,11 +1,12 @@
-use crate::docset::{DocSet, TERMINATED};
+use crate::docset::{DocSet, SkipResult};
 use crate::query::Scorer;
 use crate::DocId;
 use crate::Score;
 
-#[inline(always)]
-fn is_within<TDocSetExclude: DocSet>(docset: &mut TDocSetExclude, doc: DocId) -> bool {
-    docset.doc() <= doc && docset.seek(doc) == doc
+#[derive(Clone, Copy, Debug)]
+enum State {
+    ExcludeOne(DocId),
+    Finished,
 }
 
 /// Filters a given `DocSet` by removing the docs from a given `DocSet`.
@@ -14,6 +15,29 @@ fn is_within<TDocSetExclude: DocSet>(docset: &mut TDocSetExclude, doc: DocId) ->
 pub struct Exclude<TDocSet, TDocSetExclude> {
     underlying_docset: TDocSet,
     excluding_docset: TDocSetExclude,
+    excluding_state: State,
+}
+
+impl<TDocSet, TDocSetExclude> Exclude<TDocSet, TDocSetExclude>
+where
+    TDocSetExclude: DocSet,
+{
+    /// Creates a new `ExcludeScorer`
+    pub fn new(
+        underlying_docset: TDocSet,
+        mut excluding_docset: TDocSetExclude,
+    ) -> Exclude<TDocSet, TDocSetExclude> {
+        let state = if excluding_docset.advance() {
+            State::ExcludeOne(excluding_docset.doc())
+        } else {
+            State::Finished
+        };
+        Exclude {
+            underlying_docset,
+            excluding_docset,
+            excluding_state: state,
+        }
+    }
 }
 
 impl<TDocSet, TDocSetExclude> Exclude<TDocSet, TDocSetExclude>
@@ -21,21 +45,33 @@ where
     TDocSet: DocSet,
     TDocSetExclude: DocSet,
 {
-    /// Creates a new `ExcludeScorer`
-    pub fn new(
-        mut underlying_docset: TDocSet,
-        mut excluding_docset: TDocSetExclude,
-    ) -> Exclude<TDocSet, TDocSetExclude> {
-        while underlying_docset.doc() != TERMINATED {
-            let target = underlying_docset.doc();
-            if !is_within(&mut excluding_docset, target) {
-                break;
+    /// Returns true iff the doc is not removed.
+    ///
+    /// The method has to be called with non strictly
+    /// increasing `doc`.
+    fn accept(&mut self) -> bool {
+        let doc = self.underlying_docset.doc();
+        match self.excluding_state {
+            State::ExcludeOne(excluded_doc) => {
+                if doc == excluded_doc {
+                    return false;
+                }
+                if excluded_doc > doc {
+                    return true;
+                }
+                match self.excluding_docset.skip_next(doc) {
+                    SkipResult::OverStep => {
+                        self.excluding_state = State::ExcludeOne(self.excluding_docset.doc());
+                        true
+                    }
+                    SkipResult::End => {
+                        self.excluding_state = State::Finished;
+                        true
+                    }
+                    SkipResult::Reached => false,
+                }
             }
-            underlying_docset.advance();
-        }
-        Exclude {
-            underlying_docset,
-            excluding_docset,
+            State::Finished => true,
         }
     }
 }
@@ -45,27 +81,27 @@ where
     TDocSet: DocSet,
     TDocSetExclude: DocSet,
 {
-    fn advance(&mut self) -> DocId {
-        loop {
-            let candidate = self.underlying_docset.advance();
-            if candidate == TERMINATED {
-                return TERMINATED;
-            }
-            if !is_within(&mut self.excluding_docset, candidate) {
-                return candidate;
+    fn advance(&mut self) -> bool {
+        while self.underlying_docset.advance() {
+            if self.accept() {
+                return true;
             }
         }
+        false
     }
 
-    fn seek(&mut self, target: DocId) -> DocId {
-        let candidate = self.underlying_docset.seek(target);
-        if candidate == TERMINATED {
-            return TERMINATED;
+    fn skip_next(&mut self, target: DocId) -> SkipResult {
+        let underlying_skip_result = self.underlying_docset.skip_next(target);
+        if underlying_skip_result == SkipResult::End {
+            return SkipResult::End;
         }
-        if !is_within(&mut self.excluding_docset, candidate) {
-            return candidate;
+        if self.accept() {
+            underlying_skip_result
+        } else if self.advance() {
+            SkipResult::OverStep
+        } else {
+            SkipResult::End
         }
-        self.advance()
     }
 
     fn doc(&self) -> DocId {
@@ -105,9 +141,8 @@ mod tests {
             VecDocSet::from(vec![1, 2, 3, 10, 16, 24]),
         );
         let mut els = vec![];
-        while exclude_scorer.doc() != TERMINATED {
+        while exclude_scorer.advance() {
             els.push(exclude_scorer.doc());
-            exclude_scorer.advance();
         }
         assert_eq!(els, vec![5, 8, 15]);
     }
@@ -121,7 +156,7 @@ mod tests {
                     VecDocSet::from(vec![1, 2, 3, 10, 16, 24]),
                 ))
             },
-            vec![5, 8, 10, 15, 24],
+            vec![1, 2, 5, 8, 10, 15, 24],
         );
     }