diff --git a/milli/src/update/del_add.rs b/milli/src/update/del_add.rs
index 346ae0afa..c8b7f0f6a 100644
--- a/milli/src/update/del_add.rs
+++ b/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)
+}
diff --git a/milli/src/update/index_documents/extract/extract_word_docids.rs b/milli/src/update/index_documents/extract/extract_word_docids.rs
index a9821e2f5..462c8ae25 100644
--- a/milli/src/update/index_documents/extract/extract_word_docids.rs
+++ b/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() {
-            words.insert(word.to_vec());
+        let del_add_reader = KvReaderDelAdd::new(&value);
+        // 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()? {
-        word_fid_docids_writer.insert(key, value)?;
+        // 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(())
 }