Send directly each chunk to the main thread instead of merging them at the end of the extracting

4319: Update README r=curquiza a=codesmith-emmy

# Pull Request

## Related issue
Fixes #<issue_number>

## What does this PR do?
- ...

## PR checklist
Please check if your PR fulfills the following requirements:
- [ ] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [ ] Have you read the contributing guidelines?
- [ ] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!


Co-authored-by: emmanuel <154705254+codesmith-emmy@users.noreply.github.com>

.github/workflows/sdks-tests.yml

@@ -22,7 +22,7 @@ jobs:
     outputs:
       docker-image: ${{ steps.define-image.outputs.docker-image }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Define the Docker image we need to use
         id: define-image
         run: |
@@ -46,11 +46,11 @@ jobs:
       MEILISEARCH_VERSION: ${{ needs.define-docker-image.outputs.docker-image }}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-dotnet
       - name: Setup .NET Core
-        uses: actions/setup-dotnet@v3
+        uses: actions/setup-dotnet@v4
         with:
           dotnet-version: "6.0.x"
       - name: Install dependencies
@@ -75,12 +75,12 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-dart
       - uses: dart-lang/setup-dart@v1
         with:
-          sdk: 3.1.1
+          sdk: 'latest'
       - name: Install dependencies
         run: dart pub get
       - name: Run integration tests
@@ -100,10 +100,10 @@ jobs:
           - '7700:7700'
     steps:
       - name: Set up Go
-        uses: actions/setup-go@v4
+        uses: actions/setup-go@v5
         with:
           go-version: stable
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-go
       - name: Get dependencies
@@ -129,11 +129,11 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-java
       - name: Set up Java
-        uses: actions/setup-java@v3
+        uses: actions/setup-java@v4
         with:
           java-version: 8
           distribution: 'zulu'
@@ -156,7 +156,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-js
       - name: Setup node
@@ -191,7 +191,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-php
       - name: Install PHP
@@ -220,11 +220,11 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-python
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
       - name: Install pipenv
         uses: dschep/install-pipenv-action@v1
       - name: Install dependencies
@@ -245,7 +245,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-ruby
       - name: Set up Ruby 3
@@ -270,7 +270,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-rust
       - name: Build
@@ -291,7 +291,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-swift
       - name: Run tests
@@ -314,7 +314,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-js-plugins
       - name: Setup node
@@ -345,7 +345,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-rails
       - name: Set up Ruby 3
@@ -369,7 +369,7 @@ jobs:
         ports:
           - '7700:7700'
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           repository: meilisearch/meilisearch-symfony
       - name: Install PHP

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2019-2022 Meili SAS
+Copyright (c) 2019-2024 Meili SAS
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -42,7 +42,7 @@ Meilisearch helps you shape a delightful search experience in a snap, offering f
 
 - **Search-as-you-type:** find search results in less than 50 milliseconds
 - **[Typo tolerance](https://www.meilisearch.com/docs/learn/getting_started/customizing_relevancy?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features#typo-tolerance):** get relevant matches even when queries contain typos and misspellings
-- **[Filtering](https://www.meilisearch.com/docs/learn/fine_tuning_results/filtering?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features) and [faceted search](https://www.meilisearch.com/docs/learn/fine_tuning_results/faceted_search?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features):** enhance your user's search experience with custom filters and build a faceted search interface in a few lines of code
+- **[Filtering](https://www.meilisearch.com/docs/learn/fine_tuning_results/filtering?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features) and [faceted search](https://www.meilisearch.com/docs/learn/fine_tuning_results/faceted_search?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features):** enhance your users' search experience with custom filters and build a faceted search interface in a few lines of code
 - **[Sorting](https://www.meilisearch.com/docs/learn/fine_tuning_results/sorting?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features):** sort results based on price, date, or pretty much anything else your users need
 - **[Synonym support](https://www.meilisearch.com/docs/learn/getting_started/customizing_relevancy?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features#synonyms):** configure synonyms to include more relevant content in your search results
 - **[Geosearch](https://www.meilisearch.com/docs/learn/fine_tuning_results/geosearch?utm_campaign=oss&utm_source=github&utm_medium=meilisearch&utm_content=features):** filter and sort documents based on geographic data

index-scheduler/src/batch.rs

@@ -60,7 +60,7 @@ pub(crate) enum Batch {
         /// The list of tasks that were processing when this task cancelation appeared.
         previous_processing_tasks: RoaringBitmap,
     },
-    TaskDeletion(Task),
+    TaskDeletions(Vec<Task>),
     SnapshotCreation(Vec<Task>),
     Dump(Task),
     IndexOperation {
@@ -146,13 +146,12 @@ impl Batch {
     pub fn ids(&self) -> Vec<TaskId> {
         match self {
             Batch::TaskCancelation { task, .. }
-            | Batch::TaskDeletion(task)
             | Batch::Dump(task)
             | Batch::IndexCreation { task, .. }
             | Batch::IndexUpdate { task, .. } => vec![task.uid],
-            Batch::SnapshotCreation(tasks) | Batch::IndexDeletion { tasks, .. } => {
-                tasks.iter().map(|task| task.uid).collect()
-            }
+            Batch::SnapshotCreation(tasks)
+            | Batch::TaskDeletions(tasks)
+            | Batch::IndexDeletion { tasks, .. } => tasks.iter().map(|task| task.uid).collect(),
             Batch::IndexOperation { op, .. } => match op {
                 IndexOperation::DocumentOperation { tasks, .. }
                 | IndexOperation::Settings { tasks, .. }
@@ -180,7 +179,7 @@ impl Batch {
         use Batch::*;
         match self {
             TaskCancelation { .. }
-            | TaskDeletion(_)
+            | TaskDeletions(_)
             | SnapshotCreation(_)
             | Dump(_)
             | IndexSwap { .. } => None,
@@ -199,7 +198,7 @@ impl fmt::Display for Batch {
         let tasks = self.ids();
         match self {
             Batch::TaskCancelation { .. } => f.write_str("TaskCancelation")?,
-            Batch::TaskDeletion(_) => f.write_str("TaskDeletion")?,
+            Batch::TaskDeletions(_) => f.write_str("TaskDeletion")?,
             Batch::SnapshotCreation(_) => f.write_str("SnapshotCreation")?,
             Batch::Dump(_) => f.write_str("Dump")?,
             Batch::IndexOperation { op, .. } => write!(f, "{op}")?,
@@ -539,9 +538,9 @@ impl IndexScheduler {
 
         // 2. we get the next task to delete
         let to_delete = self.get_kind(rtxn, Kind::TaskDeletion)? & enqueued;
-        if let Some(task_id) = to_delete.min() {
-            let task = self.get_task(rtxn, task_id)?.ok_or(Error::CorruptedTaskQueue)?;
-            return Ok(Some(Batch::TaskDeletion(task)));
+        if !to_delete.is_empty() {
+            let tasks = self.get_existing_tasks(rtxn, to_delete)?;
+            return Ok(Some(Batch::TaskDeletions(tasks)));
         }
 
         // 3. we batch the snapshot.
@@ -681,31 +680,43 @@ impl IndexScheduler {
 
                 Ok(vec![task])
             }
-            Batch::TaskDeletion(mut task) => {
+            Batch::TaskDeletions(mut tasks) => {
                 // 1. Retrieve the tasks that matched the query at enqueue-time.
-                let matched_tasks =
+                let mut matched_tasks = RoaringBitmap::new();
+
+                for task in tasks.iter() {
                     if let KindWithContent::TaskDeletion { tasks, query: _ } = &task.kind {
-                        tasks
+                        matched_tasks |= tasks;
                     } else {
                         unreachable!()
+                    }
+                }
+
+                let mut wtxn = self.env.write_txn()?;
+                let mut deleted_tasks = self.delete_matched_tasks(&mut wtxn, &matched_tasks)?;
+                wtxn.commit()?;
+
+                for task in tasks.iter_mut() {
+                    task.status = Status::Succeeded;
+                    let KindWithContent::TaskDeletion { tasks, query: _ } = &task.kind else {
+                        unreachable!()
                     };
 
-                let mut wtxn = self.env.write_txn()?;
-                let deleted_tasks_count = self.delete_matched_tasks(&mut wtxn, matched_tasks)?;
+                    let deleted_tasks_count = deleted_tasks.intersection_len(tasks);
+                    deleted_tasks -= tasks;
 
-                task.status = Status::Succeeded;
-                match &mut task.details {
-                    Some(Details::TaskDeletion {
-                        matched_tasks: _,
-                        deleted_tasks,
-                        original_filter: _,
-                    }) => {
-                        *deleted_tasks = Some(deleted_tasks_count);
+                    match &mut task.details {
+                        Some(Details::TaskDeletion {
+                            matched_tasks: _,
+                            deleted_tasks,
+                            original_filter: _,
+                        }) => {
+                            *deleted_tasks = Some(deleted_tasks_count);
+                        }
+                        _ => unreachable!(),
                     }
-                    _ => unreachable!(),
                 }
-                wtxn.commit()?;
-                Ok(vec![task])
+                Ok(tasks)
             }
             Batch::SnapshotCreation(mut tasks) => {
                 fs::create_dir_all(&self.snapshots_path)?;
@@ -1435,7 +1446,11 @@ impl IndexScheduler {
     /// Delete each given task from all the databases (if it is deleteable).
     ///
     /// Return the number of tasks that were actually deleted.
-    fn delete_matched_tasks(&self, wtxn: &mut RwTxn, matched_tasks: &RoaringBitmap) -> Result<u64> {
+    fn delete_matched_tasks(
+        &self,
+        wtxn: &mut RwTxn,
+        matched_tasks: &RoaringBitmap,
+    ) -> Result<RoaringBitmap> {
         // 1. Remove from this list the tasks that we are not allowed to delete
         let enqueued_tasks = self.get_status(wtxn, Status::Enqueued)?;
         let processing_tasks = &self.processing_tasks.read().unwrap().processing.clone();
@@ -1500,7 +1515,7 @@ impl IndexScheduler {
             }
         }
 
-        Ok(to_delete_tasks.len())
+        Ok(to_delete_tasks)
     }
 
     /// Cancel each given task from all the databases (if it is cancelable).

index-scheduler/src/lib.rs

@@ -2244,10 +2244,7 @@ mod tests {
                 .unwrap();
             index_scheduler.assert_internally_consistent();
         }
-        for _ in 0..2 {
-            handle.advance_one_successful_batch();
-            index_scheduler.assert_internally_consistent();
-        }
+        handle.advance_one_successful_batch();
 
         snapshot!(snapshot_index_scheduler(&index_scheduler), name: "task_deletion_processed");
     }

index-scheduler/src/snapshots/lib.rs/task_deletion_delete_same_task_twice/task_deletion_processed.snap

@@ -34,12 +34,10 @@ catto: { number_of_documents: 1, field_distribution: {"id": 1} }
 [timestamp] [3,]
 ----------------------------------------------------------------------
 ### Started At:
-[timestamp] [2,]
-[timestamp] [3,]
+[timestamp] [2,3,]
 ----------------------------------------------------------------------
 ### Finished At:
-[timestamp] [2,]
-[timestamp] [3,]
+[timestamp] [2,3,]
 ----------------------------------------------------------------------
 ### File Store:
 00000000-0000-0000-0000-000000000001

milli/src/update/index_documents/extract/extract_docid_word_positions.rs

@@ -26,7 +26,7 @@ pub fn extract_docid_word_positions<R: io::Read + io::Seek>(
     obkv_documents: grenad::Reader<R>,
     indexer: GrenadParameters,
     searchable_fields: &Option<HashSet<FieldId>>,
-    stop_words: Option<&fst::Set<&[u8]>>,
+    stop_words: Option<&fst::Set<Vec<u8>>>,
     allowed_separators: Option<&[&str]>,
     dictionary: Option<&[&str]>,
     max_positions_per_attributes: Option<u32>,
@@ -181,11 +181,11 @@ fn searchable_fields_changed(
 
 /// Factorize tokenizer building.
 fn tokenizer_builder<'a>(
-    stop_words: Option<&'a fst::Set<&[u8]>>,
+    stop_words: Option<&'a fst::Set<Vec<u8>>>,
     allowed_separators: Option<&'a [&str]>,
     dictionary: Option<&'a [&str]>,
     script_language: Option<&'a HashMap<Script, Vec<Language>>>,
-) -> TokenizerBuilder<'a, &'a [u8]> {
+) -> TokenizerBuilder<'a, Vec<u8>> {
     let mut tokenizer_builder = TokenizerBuilder::new();
     if let Some(stop_words) = stop_words {
         tokenizer_builder.stop_words(stop_words);
@@ -211,7 +211,7 @@ fn lang_safe_tokens_from_document<'a>(
     obkv: &KvReader<FieldId>,
     searchable_fields: &Option<HashSet<FieldId>>,
     tokenizer: &Tokenizer,
-    stop_words: Option<&fst::Set<&[u8]>>,
+    stop_words: Option<&fst::Set<Vec<u8>>>,
     allowed_separators: Option<&[&str]>,
     dictionary: Option<&[&str]>,
     max_positions_per_attributes: u32,

milli/src/update/index_documents/extract/mod.rs

@@ -14,7 +14,6 @@ use std::fs::File;
 use std::io::BufReader;
 
 use crossbeam_channel::Sender;
-use log::debug;
 use rayon::prelude::*;
 
 use self::extract_docid_word_positions::extract_docid_word_positions;
@@ -29,10 +28,7 @@ use self::extract_vector_points::{
 use self::extract_word_docids::extract_word_docids;
 use self::extract_word_pair_proximity_docids::extract_word_pair_proximity_docids;
 use self::extract_word_position_docids::extract_word_position_docids;
-use super::helpers::{
-    as_cloneable_grenad, merge_deladd_cbo_roaring_bitmaps, CursorClonableMmap, GrenadParameters,
-    MergeFn, MergeableReader,
-};
+use super::helpers::{as_cloneable_grenad, CursorClonableMmap, GrenadParameters};
 use super::{helpers, TypedChunk};
 use crate::proximity::ProximityPrecision;
 use crate::vector::EmbeddingConfigs;
@@ -51,7 +47,7 @@ pub(crate) fn data_from_obkv_documents(
     primary_key_id: FieldId,
     geo_fields_ids: Option<(FieldId, FieldId)>,
     field_id_map: FieldsIdsMap,
-    stop_words: Option<fst::Set<&[u8]>>,
+    stop_words: Option<fst::Set<Vec<u8>>>,
     allowed_separators: Option<&[&str]>,
     dictionary: Option<&[&str]>,
     max_positions_per_attributes: Option<u32>,
@@ -61,218 +57,170 @@ pub(crate) fn data_from_obkv_documents(
 ) -> Result<()> {
     puffin::profile_function!();
 
-    original_obkv_chunks
-        .par_bridge()
-        .map(|original_documents_chunk| {
-            send_original_documents_data(
-                original_documents_chunk,
-                indexer,
-                lmdb_writer_sx.clone(),
-                field_id_map.clone(),
-                embedders.clone(),
-            )
-        })
-        .collect::<Result<()>>()?;
-
-    #[allow(clippy::type_complexity)]
-    let result: Result<(Vec<_>, (Vec<_>, (Vec<_>, (Vec<_>, (Vec<_>, Vec<_>)))))> =
-        flattened_obkv_chunks
-            .par_bridge()
-            .map(|flattened_obkv_chunks| {
-                send_and_extract_flattened_documents_data(
-                    flattened_obkv_chunks,
-                    indexer,
-                    lmdb_writer_sx.clone(),
-                    &searchable_fields,
-                    &faceted_fields,
-                    primary_key_id,
-                    geo_fields_ids,
-                    &stop_words,
-                    &allowed_separators,
-                    &dictionary,
-                    max_positions_per_attributes,
-                )
-            })
-            .collect();
-
-    let (
-        docid_word_positions_chunks,
-        (
-            fid_docid_facet_numbers_chunks,
-            (
-                fid_docid_facet_strings_chunks,
-                (
-                    facet_is_null_docids_chunks,
-                    (facet_is_empty_docids_chunks, facet_exists_docids_chunks),
-                ),
-            ),
-        ),
-    ) = result?;
-
-    // merge facet_exists_docids and send them as a typed chunk
-    {
-        let lmdb_writer_sx = lmdb_writer_sx.clone();
-        rayon::spawn(move || {
-            debug!("merge {} database", "facet-id-exists-docids");
-            match facet_exists_docids_chunks.merge(merge_deladd_cbo_roaring_bitmaps, &indexer) {
-                Ok(reader) => {
-                    let _ = lmdb_writer_sx.send(Ok(TypedChunk::FieldIdFacetExistsDocids(reader)));
-                }
-                Err(e) => {
-                    let _ = lmdb_writer_sx.send(Err(e));
-                }
-            }
-        });
-    }
-
-    // merge facet_is_null_docids and send them as a typed chunk
-    {
-        let lmdb_writer_sx = lmdb_writer_sx.clone();
-        rayon::spawn(move || {
-            debug!("merge {} database", "facet-id-is-null-docids");
-            match facet_is_null_docids_chunks.merge(merge_deladd_cbo_roaring_bitmaps, &indexer) {
-                Ok(reader) => {
-                    let _ = lmdb_writer_sx.send(Ok(TypedChunk::FieldIdFacetIsNullDocids(reader)));
-                }
-                Err(e) => {
-                    let _ = lmdb_writer_sx.send(Err(e));
-                }
-            }
-        });
-    }
-
-    // merge facet_is_empty_docids and send them as a typed chunk
-    {
-        let lmdb_writer_sx = lmdb_writer_sx.clone();
-        rayon::spawn(move || {
-            debug!("merge {} database", "facet-id-is-empty-docids");
-            match facet_is_empty_docids_chunks.merge(merge_deladd_cbo_roaring_bitmaps, &indexer) {
-                Ok(reader) => {
-                    let _ = lmdb_writer_sx.send(Ok(TypedChunk::FieldIdFacetIsEmptyDocids(reader)));
-                }
-                Err(e) => {
-                    let _ = lmdb_writer_sx.send(Err(e));
-                }
-            }
-        });
-    }
-
-    if proximity_precision == ProximityPrecision::ByWord {
-        spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
-            docid_word_positions_chunks.clone(),
-            indexer,
-            lmdb_writer_sx.clone(),
-            extract_word_pair_proximity_docids,
-            merge_deladd_cbo_roaring_bitmaps,
-            TypedChunk::WordPairProximityDocids,
-            "word-pair-proximity-docids",
-        );
-    }
-
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
-        docid_word_positions_chunks.clone(),
-        indexer,
-        lmdb_writer_sx.clone(),
-        extract_fid_word_count_docids,
-        merge_deladd_cbo_roaring_bitmaps,
-        TypedChunk::FieldIdWordCountDocids,
-        "field-id-wordcount-docids",
-    );
-
-    spawn_extraction_task::<
-        _,
-        _,
-        Vec<(
-            grenad::Reader<BufReader<File>>,
-            grenad::Reader<BufReader<File>>,
-            grenad::Reader<BufReader<File>>,
-        )>,
-    >(
-        docid_word_positions_chunks.clone(),
-        indexer,
-        lmdb_writer_sx.clone(),
-        move |doc_word_pos, indexer| extract_word_docids(doc_word_pos, indexer, &exact_attributes),
-        merge_deladd_cbo_roaring_bitmaps,
-        |(word_docids_reader, exact_word_docids_reader, word_fid_docids_reader)| {
-            TypedChunk::WordDocids {
-                word_docids_reader,
-                exact_word_docids_reader,
-                word_fid_docids_reader,
-            }
+    let (original_pipeline_result, flattened_pipeline_result): (Result<_>, Result<_>) = rayon::join(
+        || {
+            original_obkv_chunks
+                .par_bridge()
+                .map(|original_documents_chunk| {
+                    send_original_documents_data(
+                        original_documents_chunk,
+                        indexer,
+                        lmdb_writer_sx.clone(),
+                        field_id_map.clone(),
+                        embedders.clone(),
+                    )
+                })
+                .collect::<Result<()>>()
+        },
+        || {
+            flattened_obkv_chunks
+                .par_bridge()
+                .map(|flattened_obkv_chunks| {
+                    send_and_extract_flattened_documents_data(
+                        flattened_obkv_chunks,
+                        indexer,
+                        lmdb_writer_sx.clone(),
+                        &searchable_fields,
+                        &faceted_fields,
+                        primary_key_id,
+                        geo_fields_ids,
+                        &stop_words,
+                        &allowed_separators,
+                        &dictionary,
+                        max_positions_per_attributes,
+                    )
+                })
+                .inspect(|result| {
+                    if proximity_precision == ProximityPrecision::ByWord {
+                        if let Ok((docid_word_positions_chunk, _)) = result {
+                            run_extraction_task::<_, _, grenad::Reader<BufReader<File>>>(
+                                docid_word_positions_chunk.clone(),
+                                indexer,
+                                lmdb_writer_sx.clone(),
+                                extract_word_pair_proximity_docids,
+                                TypedChunk::WordPairProximityDocids,
+                                "word-pair-proximity-docids",
+                            );
+                        }
+                    }
+                })
+                .inspect(|result| {
+                    if let Ok((docid_word_positions_chunk, _)) = result {
+                        run_extraction_task::<_, _, grenad::Reader<BufReader<File>>>(
+                            docid_word_positions_chunk.clone(),
+                            indexer,
+                            lmdb_writer_sx.clone(),
+                            extract_fid_word_count_docids,
+                            TypedChunk::FieldIdWordCountDocids,
+                            "field-id-wordcount-docids",
+                        );
+                    }
+                })
+                .inspect(|result| {
+                    if let Ok((docid_word_positions_chunk, _)) = result {
+                        let exact_attributes = exact_attributes.clone();
+                        run_extraction_task::<
+                            _,
+                            _,
+                            (
+                                grenad::Reader<BufReader<File>>,
+                                grenad::Reader<BufReader<File>>,
+                                grenad::Reader<BufReader<File>>,
+                            ),
+                        >(
+                            docid_word_positions_chunk.clone(),
+                            indexer,
+                            lmdb_writer_sx.clone(),
+                            move |doc_word_pos, indexer| {
+                                extract_word_docids(doc_word_pos, indexer, &exact_attributes)
+                            },
+                            |(
+                                word_docids_reader,
+                                exact_word_docids_reader,
+                                word_fid_docids_reader,
+                            )| {
+                                TypedChunk::WordDocids {
+                                    word_docids_reader,
+                                    exact_word_docids_reader,
+                                    word_fid_docids_reader,
+                                }
+                            },
+                            "word-docids",
+                        );
+                    }
+                })
+                .inspect(|result| {
+                    if let Ok((docid_word_positions_chunk, _)) = result {
+                        run_extraction_task::<_, _, grenad::Reader<BufReader<File>>>(
+                            docid_word_positions_chunk.clone(),
+                            indexer,
+                            lmdb_writer_sx.clone(),
+                            extract_word_position_docids,
+                            TypedChunk::WordPositionDocids,
+                            "word-position-docids",
+                        );
+                    }
+                })
+                .inspect(|result| {
+                    if let Ok((_, (_, fid_docid_facet_strings_chunk))) = result {
+                        run_extraction_task::<_, _, grenad::Reader<BufReader<File>>>(
+                            fid_docid_facet_strings_chunk.clone(),
+                            indexer,
+                            lmdb_writer_sx.clone(),
+                            extract_facet_string_docids,
+                            TypedChunk::FieldIdFacetStringDocids,
+                            "field-id-facet-string-docids",
+                        );
+                    }
+                })
+                .inspect(|result| {
+                    if let Ok((_, (fid_docid_facet_numbers_chunk, _))) = result {
+                        run_extraction_task::<_, _, grenad::Reader<BufReader<File>>>(
+                            fid_docid_facet_numbers_chunk.clone(),
+                            indexer,
+                            lmdb_writer_sx.clone(),
+                            extract_facet_number_docids,
+                            TypedChunk::FieldIdFacetNumberDocids,
+                            "field-id-facet-number-docids",
+                        );
+                    }
+                })
+                .map(|r| r.map(|_| ()))
+                .collect::<Result<()>>()
         },
-        "word-docids",
     );
 
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
-        docid_word_positions_chunks.clone(),
-        indexer,
-        lmdb_writer_sx.clone(),
-        extract_word_position_docids,
-        merge_deladd_cbo_roaring_bitmaps,
-        TypedChunk::WordPositionDocids,
-        "word-position-docids",
-    );
-
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
-        fid_docid_facet_strings_chunks,
-        indexer,
-        lmdb_writer_sx.clone(),
-        extract_facet_string_docids,
-        merge_deladd_cbo_roaring_bitmaps,
-        TypedChunk::FieldIdFacetStringDocids,
-        "field-id-facet-string-docids",
-    );
-
-    spawn_extraction_task::<_, _, Vec<grenad::Reader<BufReader<File>>>>(
-        fid_docid_facet_numbers_chunks,
-        indexer,
-        lmdb_writer_sx,
-        extract_facet_number_docids,
-        merge_deladd_cbo_roaring_bitmaps,
-        TypedChunk::FieldIdFacetNumberDocids,
-        "field-id-facet-number-docids",
-    );
-
-    Ok(())
+    original_pipeline_result.and(flattened_pipeline_result)
 }
 
 /// Spawn a new task to extract data for a specific DB using extract_fn.
 /// Generated grenad chunks are merged using the merge_fn.
 /// The result of merged chunks is serialized as TypedChunk using the serialize_fn
 /// and sent into lmdb_writer_sx.
-fn spawn_extraction_task<FE, FS, M>(
-    chunks: Vec<grenad::Reader<CursorClonableMmap>>,
+fn run_extraction_task<FE, FS, M>(
+    chunk: grenad::Reader<CursorClonableMmap>,
     indexer: GrenadParameters,
     lmdb_writer_sx: Sender<Result<TypedChunk>>,
     extract_fn: FE,
-    merge_fn: MergeFn,
     serialize_fn: FS,
     name: &'static str,
 ) where
-    FE: Fn(grenad::Reader<CursorClonableMmap>, GrenadParameters) -> Result<M::Output>
+    FE: Fn(grenad::Reader<CursorClonableMmap>, GrenadParameters) -> Result<M>
         + Sync
         + Send
         + 'static,
-    FS: Fn(M::Output) -> TypedChunk + Sync + Send + 'static,
-    M: MergeableReader + FromParallelIterator<M::Output> + Send + 'static,
-    M::Output: Send,
+    FS: Fn(M) -> TypedChunk + Sync + Send + 'static,
+    M: Send,
 {
-    rayon::spawn(move || {
-        puffin::profile_scope!("extract_multiple_chunks", name);
-        let chunks: Result<M> =
-            chunks.into_par_iter().map(|chunk| extract_fn(chunk, indexer)).collect();
-        rayon::spawn(move || match chunks {
-            Ok(chunks) => {
-                debug!("merge {} database", name);
-                puffin::profile_scope!("merge_multiple_chunks", name);
-                let reader = chunks.merge(merge_fn, &indexer);
-                let _ = lmdb_writer_sx.send(reader.map(serialize_fn));
-            }
-            Err(e) => {
-                let _ = lmdb_writer_sx.send(Err(e));
-            }
-        })
-    });
+    puffin::profile_scope!("extract_chunk", name);
+    match extract_fn(chunk, indexer) {
+        Ok(chunk) => {
+            let _ = lmdb_writer_sx.send(Ok(serialize_fn(chunk)));
+        }
+        Err(e) => {
+            let _ = lmdb_writer_sx.send(Err(e));
+        }
+    }
 }
 
 /// Extract chunked data and send it into lmdb_writer_sx sender:
@@ -350,22 +298,13 @@ fn send_and_extract_flattened_documents_data(
     faceted_fields: &HashSet<FieldId>,
     primary_key_id: FieldId,
     geo_fields_ids: Option<(FieldId, FieldId)>,
-    stop_words: &Option<fst::Set<&[u8]>>,
+    stop_words: &Option<fst::Set<Vec<u8>>>,
     allowed_separators: &Option<&[&str]>,
     dictionary: &Option<&[&str]>,
     max_positions_per_attributes: Option<u32>,
 ) -> Result<(
     grenad::Reader<CursorClonableMmap>,
-    (
-        grenad::Reader<CursorClonableMmap>,
-        (
-            grenad::Reader<CursorClonableMmap>,
-            (
-                grenad::Reader<BufReader<File>>,
-                (grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>),
-            ),
-        ),
-    ),
+    (grenad::Reader<CursorClonableMmap>, grenad::Reader<CursorClonableMmap>),
 )> {
     let flattened_documents_chunk =
         flattened_documents_chunk.and_then(|c| unsafe { as_cloneable_grenad(&c) })?;
@@ -436,16 +375,17 @@ fn send_and_extract_flattened_documents_data(
                     fid_docid_facet_strings_chunk.clone(),
                 )));
 
-                Ok((
-                    fid_docid_facet_numbers_chunk,
-                    (
-                        fid_docid_facet_strings_chunk,
-                        (
-                            fid_facet_is_null_docids_chunk,
-                            (fid_facet_is_empty_docids_chunk, fid_facet_exists_docids_chunk),
-                        ),
-                    ),
-                ))
+                let _ = lmdb_writer_sx
+                    .send(Ok(TypedChunk::FieldIdFacetIsNullDocids(fid_facet_is_null_docids_chunk)));
+
+                let _ = lmdb_writer_sx.send(Ok(TypedChunk::FieldIdFacetIsEmptyDocids(
+                    fid_facet_is_empty_docids_chunk,
+                )));
+
+                let _ = lmdb_writer_sx
+                    .send(Ok(TypedChunk::FieldIdFacetExistsDocids(fid_facet_exists_docids_chunk)));
+
+                Ok((fid_docid_facet_numbers_chunk, fid_docid_facet_strings_chunk))
             },
         );
 

milli/src/update/index_documents/helpers/grenad_helpers.rs

@@ -82,90 +82,6 @@ pub unsafe fn as_cloneable_grenad(
     Ok(reader)
 }
 
-pub trait MergeableReader
-where
-    Self: Sized,
-{
-    type Output;
-
-    fn merge(self, merge_fn: MergeFn, indexer: &GrenadParameters) -> Result<Self::Output>;
-}
-
-impl MergeableReader for Vec<grenad::Reader<BufReader<File>>> {
-    type Output = grenad::Reader<BufReader<File>>;
-
-    fn merge(self, merge_fn: MergeFn, params: &GrenadParameters) -> Result<Self::Output> {
-        let mut merger = MergerBuilder::new(merge_fn);
-        self.into_iter().try_for_each(|r| merger.push(r))?;
-        merger.finish(params)
-    }
-}
-
-impl MergeableReader for Vec<(grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>)> {
-    type Output = (grenad::Reader<BufReader<File>>, grenad::Reader<BufReader<File>>);
-
-    fn merge(self, merge_fn: MergeFn, params: &GrenadParameters) -> Result<Self::Output> {
-        let mut m1 = MergerBuilder::new(merge_fn);
-        let mut m2 = MergerBuilder::new(merge_fn);
-        for (r1, r2) in self.into_iter() {
-            m1.push(r1)?;
-            m2.push(r2)?;
-        }
-        Ok((m1.finish(params)?, m2.finish(params)?))
-    }
-}
-
-impl MergeableReader
-    for Vec<(
-        grenad::Reader<BufReader<File>>,
-        grenad::Reader<BufReader<File>>,
-        grenad::Reader<BufReader<File>>,
-    )>
-{
-    type Output = (
-        grenad::Reader<BufReader<File>>,
-        grenad::Reader<BufReader<File>>,
-        grenad::Reader<BufReader<File>>,
-    );
-
-    fn merge(self, merge_fn: MergeFn, params: &GrenadParameters) -> Result<Self::Output> {
-        let mut m1 = MergerBuilder::new(merge_fn);
-        let mut m2 = MergerBuilder::new(merge_fn);
-        let mut m3 = MergerBuilder::new(merge_fn);
-        for (r1, r2, r3) in self.into_iter() {
-            m1.push(r1)?;
-            m2.push(r2)?;
-            m3.push(r3)?;
-        }
-        Ok((m1.finish(params)?, m2.finish(params)?, m3.finish(params)?))
-    }
-}
-
-struct MergerBuilder<R>(grenad::MergerBuilder<R, MergeFn>);
-
-impl<R: io::Read + io::Seek> MergerBuilder<R> {
-    fn new(merge_fn: MergeFn) -> Self {
-        Self(grenad::MergerBuilder::new(merge_fn))
-    }
-
-    fn push(&mut self, reader: grenad::Reader<R>) -> Result<()> {
-        self.0.push(reader.into_cursor()?);
-        Ok(())
-    }
-
-    fn finish(self, params: &GrenadParameters) -> Result<grenad::Reader<BufReader<File>>> {
-        let merger = self.0.build();
-        let mut writer = create_writer(
-            params.chunk_compression_type,
-            params.chunk_compression_level,
-            tempfile::tempfile()?,
-        );
-        merger.write_into_stream_writer(&mut writer)?;
-
-        writer_into_reader(writer)
-    }
-}
-
 #[derive(Debug, Clone, Copy)]
 pub struct GrenadParameters {
     pub chunk_compression_type: CompressionType,

milli/src/update/index_documents/helpers/mod.rs

@@ -10,7 +10,7 @@ use fst::{IntoStreamer, Streamer};
 pub use grenad_helpers::{
     as_cloneable_grenad, create_sorter, create_writer, grenad_obkv_into_chunks,
     merge_ignore_values, sorter_into_reader, write_sorter_into_database, writer_into_reader,
-    GrenadParameters, MergeableReader,
+    GrenadParameters,
 };
 pub use merge_functions::{
     keep_first, keep_latest_obkv, merge_btreeset_string, merge_cbo_roaring_bitmaps,

milli/src/update/index_documents/mod.rs

@@ -5,12 +5,13 @@ mod transform;
 mod typed_chunk;
 
 use std::collections::{HashMap, HashSet};
-use std::io::{Cursor, Read, Seek};
+use std::io::{Read, Seek};
 use std::iter::FromIterator;
 use std::num::NonZeroU32;
 use std::result::Result as StdResult;
 
 use crossbeam_channel::{Receiver, Sender};
+use grenad::{Merger, MergerBuilder};
 use heed::types::Str;
 use heed::Database;
 use log::debug;
@@ -313,9 +314,6 @@ where
             }
         };
 
-        let original_documents = grenad::Reader::new(original_documents)?;
-        let flattened_documents = grenad::Reader::new(flattened_documents)?;
-
         // create LMDB writer channel
         let (lmdb_writer_sx, lmdb_writer_rx): (
             Sender<Result<TypedChunk>>,
@@ -354,11 +352,7 @@ where
 
         let stop_words = self.index.stop_words(self.wtxn)?;
         let separators = self.index.allowed_separators(self.wtxn)?;
-        let separators: Option<Vec<_>> =
-            separators.as_ref().map(|x| x.iter().map(String::as_str).collect());
         let dictionary = self.index.dictionary(self.wtxn)?;
-        let dictionary: Option<Vec<_>> =
-            dictionary.as_ref().map(|x| x.iter().map(String::as_str).collect());
         let exact_attributes = self.index.exact_attributes_ids(self.wtxn)?;
         let proximity_precision = self.index.proximity_precision(self.wtxn)?.unwrap_or_default();
 
@@ -368,55 +362,77 @@ where
             max_memory: self.indexer_config.max_memory,
             max_nb_chunks: self.indexer_config.max_nb_chunks, // default value, may be chosen.
         };
-        let documents_chunk_size =
-            self.indexer_config.documents_chunk_size.unwrap_or(1024 * 1024 * 4); // 4MiB
+        let documents_chunk_size = match self.indexer_config.documents_chunk_size {
+            Some(chunk_size) => chunk_size,
+            None => {
+                let default_chunk_size = 1024 * 1024 * 4; // 4MiB
+                let min_chunk_size = 1024 * 512; // 512KiB
+
+                // compute the chunk size from the number of available threads and the inputed data size.
+                let total_size = flattened_documents.metadata().map(|m| m.len());
+                let current_num_threads = pool.current_num_threads();
+                total_size
+                    .map_or(default_chunk_size, |size| (size as usize) / current_num_threads)
+                    .max(min_chunk_size)
+            }
+        };
+
+        let original_documents = grenad::Reader::new(original_documents)?;
+        let flattened_documents = grenad::Reader::new(flattened_documents)?;
+
         let max_positions_per_attributes = self.indexer_config.max_positions_per_attributes;
 
         let cloned_embedder = self.embedders.clone();
 
         // Run extraction pipeline in parallel.
         pool.install(|| {
-            puffin::profile_scope!("extract_and_send_grenad_chunks");
-            // split obkv file into several chunks
-            let original_chunk_iter =
-                grenad_obkv_into_chunks(original_documents, pool_params, documents_chunk_size);
+            let stop_words = stop_words.map(|sw| sw.map_data(Vec::from).unwrap());
+            rayon::spawn(move || {
+                puffin::profile_scope!("extract_and_send_grenad_chunks");
+                // split obkv file into several chunks
+                let original_chunk_iter =
+                    grenad_obkv_into_chunks(original_documents, pool_params, documents_chunk_size);
 
-            // split obkv file into several chunks
-            let flattened_chunk_iter =
-                grenad_obkv_into_chunks(flattened_documents, pool_params, documents_chunk_size);
+                // split obkv file into several chunks
+                let flattened_chunk_iter =
+                    grenad_obkv_into_chunks(flattened_documents, pool_params, documents_chunk_size);
 
-            let result = original_chunk_iter.and_then(|original_chunk| {
-                let flattened_chunk = flattened_chunk_iter?;
-                // extract all databases from the chunked obkv douments
-                extract::data_from_obkv_documents(
-                    original_chunk,
-                    flattened_chunk,
-                    pool_params,
-                    lmdb_writer_sx.clone(),
-                    searchable_fields,
-                    faceted_fields,
-                    primary_key_id,
-                    geo_fields_ids,
-                    field_id_map,
-                    stop_words,
-                    separators.as_deref(),
-                    dictionary.as_deref(),
-                    max_positions_per_attributes,
-                    exact_attributes,
-                    proximity_precision,
-                    cloned_embedder,
-                )
+                let separators: Option<Vec<_>> =
+                    separators.as_ref().map(|x| x.iter().map(String::as_str).collect());
+                let dictionary: Option<Vec<_>> =
+                    dictionary.as_ref().map(|x| x.iter().map(String::as_str).collect());
+                let result = original_chunk_iter.and_then(|original_chunk| {
+                    let flattened_chunk = flattened_chunk_iter?;
+                    // extract all databases from the chunked obkv douments
+                    extract::data_from_obkv_documents(
+                        original_chunk,
+                        flattened_chunk,
+                        pool_params,
+                        lmdb_writer_sx.clone(),
+                        searchable_fields,
+                        faceted_fields,
+                        primary_key_id,
+                        geo_fields_ids,
+                        field_id_map,
+                        stop_words,
+                        separators.as_deref(),
+                        dictionary.as_deref(),
+                        max_positions_per_attributes,
+                        exact_attributes,
+                        proximity_precision,
+                        cloned_embedder,
+                    )
+                });
+
+                if let Err(e) = result {
+                    let _ = lmdb_writer_sx.send(Err(e));
+                }
+
+                // needs to be dropped to avoid channel waiting lock.
+                drop(lmdb_writer_sx);
             });
-
-            if let Err(e) = result {
-                let _ = lmdb_writer_sx.send(Err(e));
-            }
-
-            // needs to be dropped to avoid channel waiting lock.
-            drop(lmdb_writer_sx);
         });
 
-        let index_is_empty = self.index.number_of_documents(self.wtxn)? == 0;
         let mut final_documents_ids = RoaringBitmap::new();
 
         let mut databases_seen = 0;
@@ -444,12 +460,21 @@ where
                     word_fid_docids_reader,
                 } => {
                     let cloneable_chunk = unsafe { as_cloneable_grenad(&word_docids_reader)? };
-                    word_docids = Some(cloneable_chunk);
+                    let word_docids = word_docids.get_or_insert_with(|| {
+                        MergerBuilder::new(merge_deladd_cbo_roaring_bitmaps as MergeFn)
+                    });
+                    word_docids.push(cloneable_chunk.into_cursor()?);
                     let cloneable_chunk =
                         unsafe { as_cloneable_grenad(&exact_word_docids_reader)? };
-                    exact_word_docids = Some(cloneable_chunk);
+                    let exact_word_docids = exact_word_docids.get_or_insert_with(|| {
+                        MergerBuilder::new(merge_deladd_cbo_roaring_bitmaps as MergeFn)
+                    });
+                    exact_word_docids.push(cloneable_chunk.into_cursor()?);
                     let cloneable_chunk = unsafe { as_cloneable_grenad(&word_fid_docids_reader)? };
-                    word_fid_docids = Some(cloneable_chunk);
+                    let word_fid_docids = word_fid_docids.get_or_insert_with(|| {
+                        MergerBuilder::new(merge_deladd_cbo_roaring_bitmaps as MergeFn)
+                    });
+                    word_fid_docids.push(cloneable_chunk.into_cursor()?);
                     TypedChunk::WordDocids {
                         word_docids_reader,
                         exact_word_docids_reader,
@@ -458,7 +483,10 @@ where
                 }
                 TypedChunk::WordPositionDocids(chunk) => {
                     let cloneable_chunk = unsafe { as_cloneable_grenad(&chunk)? };
-                    word_position_docids = Some(cloneable_chunk);
+                    let word_position_docids = word_position_docids.get_or_insert_with(|| {
+                        MergerBuilder::new(merge_deladd_cbo_roaring_bitmaps as MergeFn)
+                    });
+                    word_position_docids.push(cloneable_chunk.into_cursor()?);
                     TypedChunk::WordPositionDocids(chunk)
                 }
                 TypedChunk::VectorPoints {
@@ -481,7 +509,7 @@ where
             };
 
             let (docids, is_merged_database) =
-                write_typed_chunk_into_index(typed_chunk, self.index, self.wtxn, index_is_empty)?;
+                write_typed_chunk_into_index(typed_chunk, self.index, self.wtxn)?;
             if !docids.is_empty() {
                 final_documents_ids |= docids;
                 let documents_seen_count = final_documents_ids.len();
@@ -538,10 +566,10 @@ where
         }
 
         self.execute_prefix_databases(
-            word_docids,
-            exact_word_docids,
-            word_position_docids,
-            word_fid_docids,
+            word_docids.map(MergerBuilder::build),
+            exact_word_docids.map(MergerBuilder::build),
+            word_position_docids.map(MergerBuilder::build),
+            word_fid_docids.map(MergerBuilder::build),
         )?;
 
         Ok(number_of_documents)
@@ -550,10 +578,10 @@ where
     #[logging_timer::time("IndexDocuments::{}")]
     pub fn execute_prefix_databases(
         self,
-        word_docids: Option<grenad::Reader<CursorClonableMmap>>,
-        exact_word_docids: Option<grenad::Reader<CursorClonableMmap>>,
-        word_position_docids: Option<grenad::Reader<CursorClonableMmap>>,
-        word_fid_docids: Option<grenad::Reader<CursorClonableMmap>>,
+        word_docids: Option<Merger<CursorClonableMmap, MergeFn>>,
+        exact_word_docids: Option<Merger<CursorClonableMmap, MergeFn>>,
+        word_position_docids: Option<Merger<CursorClonableMmap, MergeFn>>,
+        word_fid_docids: Option<Merger<CursorClonableMmap, MergeFn>>,
     ) -> Result<()>
     where
         FP: Fn(UpdateIndexingStep) + Sync,
@@ -728,7 +756,7 @@ where
 #[allow(clippy::too_many_arguments)]
 fn execute_word_prefix_docids(
     txn: &mut heed::RwTxn,
-    reader: grenad::Reader<Cursor<ClonableMmap>>,
+    merger: Merger<CursorClonableMmap, MergeFn>,
     word_docids_db: Database<Str, CboRoaringBitmapCodec>,
     word_prefix_docids_db: Database<Str, CboRoaringBitmapCodec>,
     indexer_config: &IndexerConfig,
@@ -738,13 +766,12 @@ fn execute_word_prefix_docids(
 ) -> Result<()> {
     puffin::profile_function!();
 
-    let cursor = reader.into_cursor()?;
     let mut builder = WordPrefixDocids::new(txn, word_docids_db, word_prefix_docids_db);
     builder.chunk_compression_type = indexer_config.chunk_compression_type;
     builder.chunk_compression_level = indexer_config.chunk_compression_level;
     builder.max_nb_chunks = indexer_config.max_nb_chunks;
     builder.max_memory = indexer_config.max_memory;
-    builder.execute(cursor, new_prefix_fst_words, common_prefix_fst_words, del_prefix_fst_words)?;
+    builder.execute(merger, new_prefix_fst_words, common_prefix_fst_words, del_prefix_fst_words)?;
     Ok(())
 }
 

milli/src/update/index_documents/typed_chunk.rs

@@ -7,7 +7,7 @@ use bytemuck::allocation::pod_collect_to_vec;
 use charabia::{Language, Script};
 use grenad::MergerBuilder;
 use heed::types::Bytes;
-use heed::{PutFlags, RwTxn};
+use heed::RwTxn;
 use obkv::{KvReader, KvWriter};
 use roaring::RoaringBitmap;
 
@@ -119,7 +119,6 @@ pub(crate) fn write_typed_chunk_into_index(
     typed_chunk: TypedChunk,
     index: &Index,
     wtxn: &mut RwTxn,
-    index_is_empty: bool,
 ) -> Result<(RoaringBitmap, bool)> {
     puffin::profile_function!(typed_chunk.to_debug_string());
 
@@ -172,11 +171,10 @@ pub(crate) fn write_typed_chunk_into_index(
             index.put_documents_ids(wtxn, &docids)?;
         }
         TypedChunk::FieldIdWordCountDocids(fid_word_count_docids_iter) => {
-            append_entries_into_database(
+            write_entries_into_database(
                 fid_word_count_docids_iter,
                 &index.field_id_word_count_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
@@ -188,31 +186,28 @@ pub(crate) fn write_typed_chunk_into_index(
             word_fid_docids_reader,
         } => {
             let word_docids_iter = unsafe { as_cloneable_grenad(&word_docids_reader) }?;
-            append_entries_into_database(
+            write_entries_into_database(
                 word_docids_iter.clone(),
                 &index.word_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
 
             let exact_word_docids_iter = unsafe { as_cloneable_grenad(&exact_word_docids_reader) }?;
-            append_entries_into_database(
+            write_entries_into_database(
                 exact_word_docids_iter.clone(),
                 &index.exact_word_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
 
             let word_fid_docids_iter = unsafe { as_cloneable_grenad(&word_fid_docids_reader) }?;
-            append_entries_into_database(
+            write_entries_into_database(
                 word_fid_docids_iter,
                 &index.word_fid_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
@@ -230,11 +225,10 @@ pub(crate) fn write_typed_chunk_into_index(
             is_merged_database = true;
         }
         TypedChunk::WordPositionDocids(word_position_docids_iter) => {
-            append_entries_into_database(
+            write_entries_into_database(
                 word_position_docids_iter,
                 &index.word_position_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
@@ -251,44 +245,40 @@ pub(crate) fn write_typed_chunk_into_index(
             is_merged_database = true;
         }
         TypedChunk::FieldIdFacetExistsDocids(facet_id_exists_docids) => {
-            append_entries_into_database(
+            write_entries_into_database(
                 facet_id_exists_docids,
                 &index.facet_id_exists_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
             is_merged_database = true;
         }
         TypedChunk::FieldIdFacetIsNullDocids(facet_id_is_null_docids) => {
-            append_entries_into_database(
+            write_entries_into_database(
                 facet_id_is_null_docids,
                 &index.facet_id_is_null_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
             is_merged_database = true;
         }
         TypedChunk::FieldIdFacetIsEmptyDocids(facet_id_is_empty_docids) => {
-            append_entries_into_database(
+            write_entries_into_database(
                 facet_id_is_empty_docids,
                 &index.facet_id_is_empty_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
             is_merged_database = true;
         }
         TypedChunk::WordPairProximityDocids(word_pair_proximity_docids_iter) => {
-            append_entries_into_database(
+            write_entries_into_database(
                 word_pair_proximity_docids_iter,
                 &index.word_pair_proximity_docids,
                 wtxn,
-                index_is_empty,
                 deladd_serialize_add_side,
                 merge_deladd_cbo_roaring_bitmaps_into_cbo_roaring_bitmap,
             )?;
@@ -541,7 +531,6 @@ fn write_entries_into_database<R, K, V, FS, FM>(
     data: grenad::Reader<R>,
     database: &heed::Database<K, V>,
     wtxn: &mut RwTxn,
-    index_is_empty: bool,
     serialize_value: FS,
     merge_values: FM,
 ) -> Result<()>
@@ -559,13 +548,9 @@ where
     while let Some((key, value)) = cursor.move_on_next()? {
         if valid_lmdb_key(key) {
             buffer.clear();
-            let value = if index_is_empty {
-                Some(serialize_value(value, &mut buffer)?)
-            } else {
-                match database.get(wtxn, key)? {
-                    Some(prev_value) => merge_values(value, prev_value, &mut buffer)?,
-                    None => Some(serialize_value(value, &mut buffer)?),
-                }
+            let value = match database.get(wtxn, key)? {
+                Some(prev_value) => merge_values(value, prev_value, &mut buffer)?,
+                None => Some(serialize_value(value, &mut buffer)?),
             };
             match value {
                 Some(value) => database.put(wtxn, key, value)?,
@@ -578,58 +563,3 @@ where
 
     Ok(())
 }
-
-/// Write provided entries in database using serialize_value function.
-/// merge_values function is used if an entry already exist in the database.
-/// All provided entries must be ordered.
-/// If the index is not empty, write_entries_into_database is called instead.
-fn append_entries_into_database<R, K, V, FS, FM>(
-    data: grenad::Reader<R>,
-    database: &heed::Database<K, V>,
-    wtxn: &mut RwTxn,
-    index_is_empty: bool,
-    serialize_value: FS,
-    merge_values: FM,
-) -> Result<()>
-where
-    R: io::Read + io::Seek,
-    FS: for<'a> Fn(&'a [u8], &'a mut Vec<u8>) -> Result<&'a [u8]>,
-    FM: for<'a> Fn(&[u8], &[u8], &'a mut Vec<u8>) -> Result<Option<&'a [u8]>>,
-    K: for<'a> heed::BytesDecode<'a>,
-{
-    puffin::profile_function!(format!("number of entries: {}", data.len()));
-
-    if !index_is_empty {
-        return write_entries_into_database(
-            data,
-            database,
-            wtxn,
-            false,
-            serialize_value,
-            merge_values,
-        );
-    }
-
-    let mut buffer = Vec::new();
-    let mut database = database.iter_mut(wtxn)?.remap_types::<Bytes, Bytes>();
-
-    let mut cursor = data.into_cursor()?;
-    while let Some((key, value)) = cursor.move_on_next()? {
-        if valid_lmdb_key(key) {
-            debug_assert!(
-                K::bytes_decode(key).is_ok(),
-                "Couldn't decode key with the database decoder, key length: {} - key bytes: {:x?}",
-                key.len(),
-                &key
-            );
-            buffer.clear();
-            let value = serialize_value(value, &mut buffer)?;
-            unsafe {
-                // safety: We do not keep a reference to anything that lives inside the database
-                database.put_current_with_options::<Bytes>(PutFlags::APPEND, key, value)?
-            };
-        }
-    }
-
-    Ok(())
-}

milli/src/update/word_prefix_docids.rs

@@ -42,7 +42,7 @@ impl<'t, 'i> WordPrefixDocids<'t, 'i> {
     #[logging_timer::time("WordPrefixDocids::{}")]
     pub fn execute(
         self,
-        mut new_word_docids_iter: grenad::ReaderCursor<CursorClonableMmap>,
+        new_word_docids: grenad::Merger<CursorClonableMmap, MergeFn>,
         new_prefix_fst_words: &[String],
         common_prefix_fst_words: &[&[String]],
         del_prefix_fst_words: &HashSet<Vec<u8>>,
@@ -63,7 +63,8 @@ impl<'t, 'i> WordPrefixDocids<'t, 'i> {
         if !common_prefix_fst_words.is_empty() {
             let mut current_prefixes: Option<&&[String]> = None;
             let mut prefixes_cache = HashMap::new();
-            while let Some((word, data)) = new_word_docids_iter.move_on_next()? {
+            let mut new_word_docids_iter = new_word_docids.into_stream_merger_iter()?;
+            while let Some((word, data)) = new_word_docids_iter.next()? {
                 current_prefixes = match current_prefixes.take() {
                     Some(prefixes) if word.starts_with(prefixes[0].as_bytes()) => Some(prefixes),
                     _otherwise => {

milli/src/update/words_prefix_integer_docids.rs

@@ -47,7 +47,7 @@ impl<'t, 'i> WordPrefixIntegerDocids<'t, 'i> {
     #[logging_timer::time("WordPrefixIntegerDocids::{}")]
     pub fn execute(
         self,
-        new_word_integer_docids: grenad::Reader<CursorClonableMmap>,
+        new_word_integer_docids: grenad::Merger<CursorClonableMmap, MergeFn>,
         new_prefix_fst_words: &[String],
         common_prefix_fst_words: &[&[String]],
         del_prefix_fst_words: &HashSet<Vec<u8>>,
@@ -64,14 +64,14 @@ impl<'t, 'i> WordPrefixIntegerDocids<'t, 'i> {
             self.max_memory,
         );
 
-        let mut new_word_integer_docids_iter = new_word_integer_docids.into_cursor()?;
-
         if !common_prefix_fst_words.is_empty() {
             // We fetch all the new common prefixes between the previous and new prefix fst.
             let mut buffer = Vec::new();
             let mut current_prefixes: Option<&&[String]> = None;
             let mut prefixes_cache = HashMap::new();
-            while let Some((key, data)) = new_word_integer_docids_iter.move_on_next()? {
+            let mut new_word_integer_docids_iter =
+                new_word_integer_docids.into_stream_merger_iter()?;
+            while let Some((key, data)) = new_word_integer_docids_iter.next()? {
                 let (word, pos) =
                     StrBEU16Codec::bytes_decode(key).map_err(heed::Error::Decoding)?;