Merge pull request #4141 from meilisearch/diff-indexing-searchable

Diff indexing searchable

milli/src/update/del_add.rs

@@ -98,3 +98,7 @@ pub fn del_add_from_two_obkvs<K: obkv::Key + PartialOrd + Ord>(
 
     writer.finish()
 }
+
+pub fn is_noop_del_add_obkv(del_add: KvReaderDelAdd) -> bool {
+    del_add.get(DelAdd::Deletion) == del_add.get(DelAdd::Addition)
+}

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

@@ -13,7 +13,7 @@ use crate::error::{InternalError, SerializationError};
 use crate::update::del_add::{del_add_from_two_obkvs, DelAdd, KvReaderDelAdd};
 use crate::{FieldId, Result, MAX_POSITION_PER_ATTRIBUTE, MAX_WORD_LENGTH};
 
-pub type ScriptLanguageDocidsMap = HashMap<(Script, Language), RoaringBitmap>;
+pub type ScriptLanguageDocidsMap = HashMap<(Script, Language), (RoaringBitmap, RoaringBitmap)>;
 
 /// Extracts the word and positions where this word appear and
 /// prefixes it by the document id.
@@ -29,8 +29,7 @@ pub fn extract_docid_word_positions<R: io::Read + io::Seek>(
     allowed_separators: Option<&[&str]>,
     dictionary: Option<&[&str]>,
     max_positions_per_attributes: Option<u32>,
-) -> Result<(RoaringBitmap, grenad::Reader<File>, (ScriptLanguageDocidsMap, ScriptLanguageDocidsMap))>
+) -> Result<(RoaringBitmap, grenad::Reader<File>, ScriptLanguageDocidsMap)> {
-{
     puffin::profile_function!();
 
     let max_positions_per_attributes = max_positions_per_attributes
@@ -39,8 +38,7 @@ pub fn extract_docid_word_positions<R: io::Read + io::Seek>(
 
     // initialize destination values.
     let mut documents_ids = RoaringBitmap::new();
-    let mut del_script_language_docids = HashMap::new();
+    let mut script_language_docids = HashMap::new();
-    let mut add_script_language_docids = HashMap::new();
     let mut docid_word_positions_sorter = create_sorter(
         grenad::SortAlgorithm::Stable,
         keep_latest_obkv,
@@ -134,25 +132,24 @@ pub fn extract_docid_word_positions<R: io::Read + io::Seek>(
         // update script_language_docids deletions.
         for (script, languages_frequency) in del_script_language_word_count {
             for (language, _) in languages_frequency {
-                let entry = del_script_language_docids
+                let entry = script_language_docids
                     .entry((script, language))
-                    .or_insert_with(RoaringBitmap::new);
+                    .or_insert_with(|| (RoaringBitmap::new(), RoaringBitmap::new()));
-                entry.push(document_id);
+                entry.0.push(document_id);
             }
         }
 
         // update script_language_docids additions.
         for (script, languages_frequency) in add_script_language_word_count {
             for (language, _) in languages_frequency {
-                let entry = add_script_language_docids
+                let entry = script_language_docids
                     .entry((script, language))
-                    .or_insert_with(RoaringBitmap::new);
+                    .or_insert_with(|| (RoaringBitmap::new(), RoaringBitmap::new()));
-                entry.push(document_id);
+                entry.1.push(document_id);
             }
         }
     }
 
-    let script_language_docids = (del_script_language_docids, add_script_language_docids);
     sorter_into_reader(docid_word_positions_sorter, indexer)
         .map(|reader| (documents_ids, reader, script_language_docids))
 }

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

@@ -6,12 +6,13 @@ use heed::BytesDecode;
 use obkv::KvReaderU16;
 
 use super::helpers::{
-    create_sorter, create_writer, merge_cbo_roaring_bitmaps, sorter_into_reader,
+    create_sorter, create_writer, merge_deladd_cbo_roaring_bitmaps, sorter_into_reader,
     try_split_array_at, writer_into_reader, GrenadParameters,
 };
 use crate::error::SerializationError;
 use crate::heed_codec::StrBEU16Codec;
 use crate::index::db_name::DOCID_WORD_POSITIONS;
+use crate::update::del_add::{is_noop_del_add_obkv, DelAdd, KvReaderDelAdd, KvWriterDelAdd};
 use crate::update::MergeFn;
 use crate::{DocumentId, FieldId, Result};
 
@@ -34,14 +35,15 @@ pub fn extract_word_docids<R: io::Read + io::Seek>(
 
     let mut word_fid_docids_sorter = create_sorter(
         grenad::SortAlgorithm::Unstable,
-        merge_cbo_roaring_bitmaps,
+        merge_deladd_cbo_roaring_bitmaps,
         indexer.chunk_compression_type,
         indexer.chunk_compression_level,
         indexer.max_nb_chunks,
         max_memory.map(|x| x / 3),
     );
     let mut key_buffer = Vec::new();
-    let mut words = BTreeSet::new();
+    let mut del_words = BTreeSet::new();
+    let mut add_words = BTreeSet::new();
     let mut cursor = docid_word_positions.into_cursor()?;
     while let Some((key, value)) = cursor.move_on_next()? {
         let (document_id_bytes, fid_bytes) = try_split_array_at(key)
@@ -51,24 +53,37 @@ pub fn extract_word_docids<R: io::Read + io::Seek>(
         let document_id = u32::from_be_bytes(document_id_bytes);
         let fid = u16::from_be_bytes(fid_bytes);
 
-        for (_pos, word) in KvReaderU16::new(&value).iter() {
+        let del_add_reader = KvReaderDelAdd::new(&value);
-            words.insert(word.to_vec());
+        // extract all unique words to remove.
+        if let Some(deletion) = del_add_reader.get(DelAdd::Deletion) {
+            for (_pos, word) in KvReaderU16::new(&deletion).iter() {
+                del_words.insert(word.to_vec());
+            }
+        }
+
+        // extract all unique additional words.
+        if let Some(addition) = del_add_reader.get(DelAdd::Addition) {
+            for (_pos, word) in KvReaderU16::new(&addition).iter() {
+                add_words.insert(word.to_vec());
+            }
         }
 
         words_into_sorter(
             document_id,
             fid,
             &mut key_buffer,
-            &mut words,
+            &del_words,
+            &add_words,
             &mut word_fid_docids_sorter,
         )?;
 
-        words.clear();
+        del_words.clear();
+        add_words.clear();
     }
 
     let mut word_docids_sorter = create_sorter(
         grenad::SortAlgorithm::Unstable,
-        merge_cbo_roaring_bitmaps,
+        merge_deladd_cbo_roaring_bitmaps,
         indexer.chunk_compression_type,
         indexer.chunk_compression_level,
         indexer.max_nb_chunks,
@@ -77,7 +92,7 @@ pub fn extract_word_docids<R: io::Read + io::Seek>(
 
     let mut exact_word_docids_sorter = create_sorter(
         grenad::SortAlgorithm::Unstable,
-        merge_cbo_roaring_bitmaps,
+        merge_deladd_cbo_roaring_bitmaps,
         indexer.chunk_compression_type,
         indexer.chunk_compression_level,
         indexer.max_nb_chunks,
@@ -91,8 +106,12 @@ pub fn extract_word_docids<R: io::Read + io::Seek>(
     );
 
     let mut iter = word_fid_docids_sorter.into_stream_merger_iter()?;
+    // TODO: replace sorters by writers by accumulating values into a buffer before inserting them.
     while let Some((key, value)) = iter.next()? {
+        // only keep the value if their is a change to apply in the DB.
+        if !is_noop_del_add_obkv(KvReaderDelAdd::new(value)) {
             word_fid_docids_writer.insert(key, value)?;
+        }
 
         let (word, fid) = StrBEU16Codec::bytes_decode(key)
             .ok_or(SerializationError::Decoding { db_name: Some(DOCID_WORD_POSITIONS) })?;
@@ -116,20 +135,41 @@ fn words_into_sorter(
     document_id: DocumentId,
     fid: FieldId,
     key_buffer: &mut Vec<u8>,
-    words: &mut BTreeSet<Vec<u8>>,
+    del_words: &BTreeSet<Vec<u8>>,
+    add_words: &BTreeSet<Vec<u8>>,
     word_fid_docids_sorter: &mut grenad::Sorter<MergeFn>,
 ) -> Result<()> {
     puffin::profile_function!();
 
-    for word_bytes in words.iter() {
+    use itertools::merge_join_by;
+    use itertools::EitherOrBoth::{Both, Left, Right};
+
+    let mut buffer = Vec::new();
+    for eob in merge_join_by(del_words.iter(), add_words.iter(), |d, a| d.cmp(a)) {
+        buffer.clear();
+        let mut value_writer = KvWriterDelAdd::new(&mut buffer);
+        let word_bytes = match eob {
+            Left(word_bytes) => {
+                value_writer.insert(DelAdd::Deletion, document_id.to_ne_bytes()).unwrap();
+                word_bytes
+            }
+            Right(word_bytes) => {
+                value_writer.insert(DelAdd::Addition, document_id.to_ne_bytes()).unwrap();
+                word_bytes
+            }
+            Both(word_bytes, _) => {
+                value_writer.insert(DelAdd::Deletion, document_id.to_ne_bytes()).unwrap();
+                value_writer.insert(DelAdd::Addition, document_id.to_ne_bytes()).unwrap();
+                word_bytes
+            }
+        };
+
         key_buffer.clear();
         key_buffer.extend_from_slice(&word_bytes);
         key_buffer.push(0);
         key_buffer.extend_from_slice(&fid.to_be_bytes());
-        word_fid_docids_sorter.insert(&key_buffer, document_id.to_ne_bytes())?;
+        word_fid_docids_sorter.insert(&key_buffer, value_writer.into_inner().unwrap())?;
     }
 
-    words.clear();
-
     Ok(())
 }

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

@@ -1,16 +1,17 @@
-use std::collections::{HashMap, VecDeque};
+use std::collections::{BTreeMap, VecDeque};
 use std::fs::File;
 use std::{cmp, io};
 
 use obkv::KvReaderU16;
 
 use super::helpers::{
-    create_sorter, create_writer, merge_cbo_roaring_bitmaps, sorter_into_reader,
+    create_sorter, create_writer, merge_deladd_cbo_roaring_bitmaps, try_split_array_at,
-    try_split_array_at, writer_into_reader, GrenadParameters, MergeFn,
+    writer_into_reader, GrenadParameters, MergeFn,
 };
 use crate::error::SerializationError;
 use crate::index::db_name::DOCID_WORD_POSITIONS;
 use crate::proximity::{index_proximity, MAX_DISTANCE};
+use crate::update::del_add::{DelAdd, KvReaderDelAdd, KvWriterDelAdd};
 use crate::{DocumentId, Result};
 
 /// Extracts the best proximity between pairs of words and the documents ids where this pair appear.
@@ -31,7 +32,7 @@ pub fn extract_word_pair_proximity_docids<R: io::Read + io::Seek>(
         .map(|_| {
             create_sorter(
                 grenad::SortAlgorithm::Unstable,
-                merge_cbo_roaring_bitmaps,
+                merge_deladd_cbo_roaring_bitmaps,
                 indexer.chunk_compression_type,
                 indexer.chunk_compression_level,
                 indexer.max_nb_chunks,
@@ -40,9 +41,12 @@ pub fn extract_word_pair_proximity_docids<R: io::Read + io::Seek>(
         })
         .collect();
 
-    let mut word_positions: VecDeque<(String, u16)> =
+    let mut del_word_positions: VecDeque<(String, u16)> =
         VecDeque::with_capacity(MAX_DISTANCE as usize);
-    let mut word_pair_proximity = HashMap::new();
+    let mut add_word_positions: VecDeque<(String, u16)> =
+        VecDeque::with_capacity(MAX_DISTANCE as usize);
+    let mut del_word_pair_proximity = BTreeMap::new();
+    let mut add_word_pair_proximity = BTreeMap::new();
     let mut current_document_id = None;
 
     let mut cursor = docid_word_positions.into_cursor()?;
@@ -54,50 +58,90 @@ pub fn extract_word_pair_proximity_docids<R: io::Read + io::Seek>(
         // if we change document, we fill the sorter
         if current_document_id.map_or(false, |id| id != document_id) {
             puffin::profile_scope!("Document into sorter");
-            while !word_positions.is_empty() {
-                word_positions_into_word_pair_proximity(
-                    &mut word_positions,
-                    &mut word_pair_proximity,
-                )?;
-            }
 
             document_word_positions_into_sorter(
                 current_document_id.unwrap(),
-                &word_pair_proximity,
+                &del_word_pair_proximity,
+                &add_word_pair_proximity,
                 &mut word_pair_proximity_docids_sorters,
             )?;
-            word_pair_proximity.clear();
+            del_word_pair_proximity.clear();
-            word_positions.clear();
+            add_word_pair_proximity.clear();
         }
 
         current_document_id = Some(document_id);
 
-        for (position, word) in KvReaderU16::new(&value).iter() {
+        let (del, add): (Result<_>, Result<_>) = rayon::join(
+            || {
+                // deletions
+                if let Some(deletion) = KvReaderDelAdd::new(&value).get(DelAdd::Deletion) {
+                    for (position, word) in KvReaderU16::new(deletion).iter() {
                         // drain the proximity window until the head word is considered close to the word we are inserting.
-            while word_positions.get(0).map_or(false, |(_w, p)| {
+                        while del_word_positions.get(0).map_or(false, |(_w, p)| {
                             index_proximity(*p as u32, position as u32) >= MAX_DISTANCE
                         }) {
                             word_positions_into_word_pair_proximity(
-                    &mut word_positions,
+                                &mut del_word_positions,
-                    &mut word_pair_proximity,
+                                &mut del_word_pair_proximity,
                             )?;
                         }
 
                         // insert the new word.
                         let word = std::str::from_utf8(word)?;
-            word_positions.push_back((word.to_string(), position));
+                        del_word_positions.push_back((word.to_string(), position));
                     }
+
+                    while !del_word_positions.is_empty() {
+                        word_positions_into_word_pair_proximity(
+                            &mut del_word_positions,
+                            &mut del_word_pair_proximity,
+                        )?;
+                    }
+                }
+
+                Ok(())
+            },
+            || {
+                // additions
+                if let Some(addition) = KvReaderDelAdd::new(&value).get(DelAdd::Addition) {
+                    for (position, word) in KvReaderU16::new(addition).iter() {
+                        // drain the proximity window until the head word is considered close to the word we are inserting.
+                        while add_word_positions.get(0).map_or(false, |(_w, p)| {
+                            index_proximity(*p as u32, position as u32) >= MAX_DISTANCE
+                        }) {
+                            word_positions_into_word_pair_proximity(
+                                &mut add_word_positions,
+                                &mut add_word_pair_proximity,
+                            )?;
+                        }
+
+                        // insert the new word.
+                        let word = std::str::from_utf8(word)?;
+                        add_word_positions.push_back((word.to_string(), position));
+                    }
+
+                    while !add_word_positions.is_empty() {
+                        word_positions_into_word_pair_proximity(
+                            &mut add_word_positions,
+                            &mut add_word_pair_proximity,
+                        )?;
+                    }
+                }
+
+                Ok(())
+            },
+        );
+
+        del?;
+        add?;
     }
 
     if let Some(document_id) = current_document_id {
         puffin::profile_scope!("Final document into sorter");
-        while !word_positions.is_empty() {
-            word_positions_into_word_pair_proximity(&mut word_positions, &mut word_pair_proximity)?;
-        }
-
         document_word_positions_into_sorter(
             document_id,
-            &word_pair_proximity,
+            &del_word_pair_proximity,
+            &add_word_pair_proximity,
             &mut word_pair_proximity_docids_sorters,
         )?;
     }
@@ -123,11 +167,38 @@ pub fn extract_word_pair_proximity_docids<R: io::Read + io::Seek>(
 /// close to each other.
 fn document_word_positions_into_sorter(
     document_id: DocumentId,
-    word_pair_proximity: &HashMap<(String, String), u8>,
+    del_word_pair_proximity: &BTreeMap<(String, String), u8>,
+    add_word_pair_proximity: &BTreeMap<(String, String), u8>,
     word_pair_proximity_docids_sorters: &mut Vec<grenad::Sorter<MergeFn>>,
 ) -> Result<()> {
+    use itertools::merge_join_by;
+    use itertools::EitherOrBoth::{Both, Left, Right};
+
+    let mut buffer = Vec::new();
     let mut key_buffer = Vec::new();
-    for ((w1, w2), prox) in word_pair_proximity {
+    for eob in
+        merge_join_by(del_word_pair_proximity.iter(), add_word_pair_proximity.iter(), |d, a| {
+            d.cmp(a)
+        })
+    {
+        buffer.clear();
+        let mut value_writer = KvWriterDelAdd::new(&mut buffer);
+        let ((w1, w2), prox) = match eob {
+            Left(key_value) => {
+                value_writer.insert(DelAdd::Deletion, document_id.to_ne_bytes()).unwrap();
+                key_value
+            }
+            Right(key_value) => {
+                value_writer.insert(DelAdd::Addition, document_id.to_ne_bytes()).unwrap();
+                key_value
+            }
+            Both(key_value, _) => {
+                value_writer.insert(DelAdd::Deletion, document_id.to_ne_bytes()).unwrap();
+                value_writer.insert(DelAdd::Addition, document_id.to_ne_bytes()).unwrap();
+                key_value
+            }
+        };
+
         key_buffer.clear();
         key_buffer.push(*prox as u8);
         key_buffer.extend_from_slice(w1.as_bytes());
@@ -135,7 +206,7 @@ fn document_word_positions_into_sorter(
         key_buffer.extend_from_slice(w2.as_bytes());
 
         word_pair_proximity_docids_sorters[*prox as usize - 1]
-            .insert(&key_buffer, document_id.to_ne_bytes())?;
+            .insert(&key_buffer, value_writer.into_inner().unwrap())?;
     }
 
     Ok(())
@@ -143,7 +214,7 @@ fn document_word_positions_into_sorter(
 
 fn word_positions_into_word_pair_proximity(
     word_positions: &mut VecDeque<(String, u16)>,
-    word_pair_proximity: &mut HashMap<(String, String), u8>,
+    word_pair_proximity: &mut BTreeMap<(String, String), u8>,
 ) -> Result<()> {
     let (head_word, head_position) = word_positions.pop_front().unwrap();
     for (word, position) in word_positions.iter() {

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

@@ -1,15 +1,17 @@
-use std::collections::HashSet;
+use std::collections::BTreeSet;
 use std::fs::File;
 use std::io;
 
 use obkv::KvReaderU16;
 
 use super::helpers::{
-    create_sorter, merge_cbo_roaring_bitmaps, sorter_into_reader, try_split_array_at,
+    create_sorter, merge_deladd_cbo_roaring_bitmaps, sorter_into_reader, try_split_array_at,
     GrenadParameters,
 };
 use crate::error::SerializationError;
 use crate::index::db_name::DOCID_WORD_POSITIONS;
+use crate::update::del_add::{DelAdd, KvReaderDelAdd, KvWriterDelAdd};
+use crate::update::MergeFn;
 use crate::{bucketed_position, DocumentId, Result};
 
 /// Extracts the word positions and the documents ids where this word appear.
@@ -27,14 +29,15 @@ pub fn extract_word_position_docids<R: io::Read + io::Seek>(
 
     let mut word_position_docids_sorter = create_sorter(
         grenad::SortAlgorithm::Unstable,
-        merge_cbo_roaring_bitmaps,
+        merge_deladd_cbo_roaring_bitmaps,
         indexer.chunk_compression_type,
         indexer.chunk_compression_level,
         indexer.max_nb_chunks,
         max_memory,
     );
 
-    let mut word_positions: HashSet<(u16, Vec<u8>)> = HashSet::new();
+    let mut del_word_positions: BTreeSet<(u16, Vec<u8>)> = BTreeSet::new();
+    let mut add_word_positions: BTreeSet<(u16, Vec<u8>)> = BTreeSet::new();
     let mut current_document_id: Option<u32> = None;
     let mut key_buffer = Vec::new();
     let mut cursor = docid_word_positions.into_cursor()?;
@@ -44,36 +47,92 @@ pub fn extract_word_position_docids<R: io::Read + io::Seek>(
         let document_id = DocumentId::from_be_bytes(document_id_bytes);
 
         if current_document_id.map_or(false, |id| document_id != id) {
-            for (position, word_bytes) in word_positions.iter() {
+            words_position_into_sorter(
-                key_buffer.clear();
+                current_document_id.unwrap(),
-                key_buffer.extend_from_slice(word_bytes);
+                &mut key_buffer,
-                key_buffer.push(0);
+                &del_word_positions,
-                key_buffer.extend_from_slice(&position.to_be_bytes());
+                &add_word_positions,
-                word_position_docids_sorter
+                &mut word_position_docids_sorter,
-                    .insert(&key_buffer, current_document_id.unwrap().to_ne_bytes())?;
+            )?;
-            }
+            del_word_positions.clear();
-            word_positions.clear();
+            add_word_positions.clear();
         }
 
         current_document_id = Some(document_id);
 
-        for (position, word_bytes) in KvReaderU16::new(&value).iter() {
+        let del_add_reader = KvReaderDelAdd::new(&value);
+        // extract all unique words to remove.
+        if let Some(deletion) = del_add_reader.get(DelAdd::Deletion) {
+            for (position, word_bytes) in KvReaderU16::new(deletion).iter() {
                 let position = bucketed_position(position);
-            word_positions.insert((position, word_bytes.to_vec()));
+                del_word_positions.insert((position, word_bytes.to_vec()));
+            }
+        }
+
+        // extract all unique additional words.
+        if let Some(addition) = del_add_reader.get(DelAdd::Addition) {
+            for (position, word_bytes) in KvReaderU16::new(addition).iter() {
+                let position = bucketed_position(position);
+                add_word_positions.insert((position, word_bytes.to_vec()));
+            }
         }
     }
 
     if let Some(document_id) = current_document_id {
-        for (position, word_bytes) in word_positions {
+        words_position_into_sorter(
-            key_buffer.clear();
+            document_id,
-            key_buffer.extend_from_slice(&word_bytes);
+            &mut key_buffer,
-            key_buffer.push(0);
+            &del_word_positions,
-            key_buffer.extend_from_slice(&position.to_be_bytes());
+            &add_word_positions,
-            word_position_docids_sorter.insert(&key_buffer, document_id.to_ne_bytes())?;
+            &mut word_position_docids_sorter,
-        }
+        )?;
     }
 
+    // TODO remove noop DelAdd OBKV
     let word_position_docids_reader = sorter_into_reader(word_position_docids_sorter, indexer)?;
 
     Ok(word_position_docids_reader)
 }
+
+fn words_position_into_sorter(
+    document_id: DocumentId,
+    key_buffer: &mut Vec<u8>,
+    del_word_positions: &BTreeSet<(u16, Vec<u8>)>,
+    add_word_positions: &BTreeSet<(u16, Vec<u8>)>,
+    word_position_docids_sorter: &mut grenad::Sorter<MergeFn>,
+) -> Result<()> {
+    puffin::profile_function!();
+
+    use itertools::merge_join_by;
+    use itertools::EitherOrBoth::{Both, Left, Right};
+
+    let mut buffer = Vec::new();
+    for eob in merge_join_by(del_word_positions.iter(), add_word_positions.iter(), |d, a| d.cmp(a))
+    {
+        buffer.clear();
+        let mut value_writer = KvWriterDelAdd::new(&mut buffer);
+        let (position, word_bytes) = match eob {
+            Left(key) => {
+                value_writer.insert(DelAdd::Deletion, document_id.to_ne_bytes()).unwrap();
+                key
+            }
+            Right(key) => {
+                value_writer.insert(DelAdd::Addition, document_id.to_ne_bytes()).unwrap();
+                key
+            }
+            Both(key, _) => {
+                value_writer.insert(DelAdd::Deletion, document_id.to_ne_bytes()).unwrap();
+                value_writer.insert(DelAdd::Addition, document_id.to_ne_bytes()).unwrap();
+                key
+            }
+        };
+
+        key_buffer.clear();
+        key_buffer.extend_from_slice(word_bytes);
+        key_buffer.push(0);
+        key_buffer.extend_from_slice(&position.to_be_bytes());
+        word_position_docids_sorter.insert(&key_buffer, value_writer.into_inner().unwrap())?;
+    }
+
+    Ok(())
+}

milli/src/update/index_documents/typed_chunk.rs

@@ -43,9 +43,7 @@ pub(crate) enum TypedChunk {
     FieldIdFacetIsEmptyDocids(grenad::Reader<File>),
     GeoPoints(grenad::Reader<File>),
     VectorPoints(grenad::Reader<File>),
-    ScriptLanguageDocids(
+    ScriptLanguageDocids(HashMap<(Script, Language), (RoaringBitmap, RoaringBitmap)>),
-        (HashMap<(Script, Language), RoaringBitmap>, HashMap<(Script, Language), RoaringBitmap>),
-    ),
 }
 
 impl TypedChunk {
@@ -103,8 +101,8 @@ impl TypedChunk {
             TypedChunk::VectorPoints(grenad) => {
                 format!("VectorPoints {{ number_of_entries: {} }}", grenad.len())
             }
-            TypedChunk::ScriptLanguageDocids((_, addition)) => {
+            TypedChunk::ScriptLanguageDocids(sl_map) => {
-                format!("ScriptLanguageDocids {{ number_of_entries: {} }}", addition.len())
+                format!("ScriptLanguageDocids {{ number_of_entries: {} }}", sl_map.len())
             }
         }
     }
@@ -346,27 +344,28 @@ pub(crate) fn write_typed_chunk_into_index(
             log::debug!("There are {} entries in the HNSW so far", hnsw_length);
             index.put_vector_hnsw(wtxn, &new_hnsw)?;
         }
-        TypedChunk::ScriptLanguageDocids((deletion, addition)) => {
+        TypedChunk::ScriptLanguageDocids(sl_map) => {
-            for (key, value) in deletion {
+            for (key, (deletion, addition)) in sl_map {
-                if let Some(mut db_values) = index.script_language_docids.get(wtxn, &key)? {
+                let mut db_key_exists = false;
-                    db_values -= value;
-                    if db_values.is_empty() {
-                        index.script_language_docids.delete(wtxn, &key)?;
-                    } else {
-                        index.script_language_docids.put(wtxn, &key, &db_values)?;
-                    }
-                }
-            }
-
-            for (key, value) in addition {
                 let final_value = match index.script_language_docids.get(wtxn, &key)? {
-                    Some(mut db_values) => db_values | value,
+                    Some(db_values) => {
-                    None => value,
+                        db_key_exists = true;
+                        (db_values - deletion) | addition
+                    }
+                    None => addition,
                 };
+
+                if final_value.is_empty() {
+                    // If the database entry exists, delete it.
+                    if db_key_exists == true {
+                        index.script_language_docids.delete(wtxn, &key)?;
+                    }
+                } else {
                     index.script_language_docids.put(wtxn, &key, &final_value)?;
                 }
             }
         }
+    }
 
     Ok((RoaringBitmap::new(), is_merged_database))
 }
@@ -388,13 +387,6 @@ fn merge_word_docids_reader_into_fst(
     Ok(builder.into_set())
 }
 
-fn merge_roaring_bitmaps(new_value: &[u8], db_value: &[u8], buffer: &mut Vec<u8>) -> Result<()> {
-    let new_value = RoaringBitmap::deserialize_from(new_value)?;
-    let db_value = RoaringBitmap::deserialize_from(db_value)?;
-    let value = new_value | db_value;
-    Ok(serialize_roaring_bitmap(&value, buffer)?)
-}
-
 fn merge_cbo_roaring_bitmaps(
     new_value: &[u8],
     db_value: &[u8],