Write the NULL facet values in the database

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

@@ -99,6 +99,22 @@ pub(crate) fn data_from_obkv_documents(
         });
     }
 
+    // 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_cbo_roaring_bitmaps, &indexer) {
+                Ok(reader) => {
+                    let _ = lmdb_writer_sx.send(Ok(TypedChunk::FieldIdFacetIsNullDocids(reader)));
+                }
+                Err(e) => {
+                    let _ = lmdb_writer_sx.send(Err(e));
+                }
+            }
+        });
+    }
+
     spawn_extraction_task::<_, _, Vec<grenad::Reader<File>>>(
         docid_word_positions_chunks.clone(),
         indexer,

milli/src/update/index_documents/typed_chunk.rs

@@ -39,6 +39,7 @@ pub(crate) enum TypedChunk {
     FieldIdFacetStringDocids(grenad::Reader<File>),
     FieldIdFacetNumberDocids(grenad::Reader<File>),
     FieldIdFacetExistsDocids(grenad::Reader<File>),
+    FieldIdFacetIsNullDocids(grenad::Reader<File>),
     GeoPoints(grenad::Reader<File>),
     ScriptLanguageDocids(HashMap<(Script, Language), RoaringBitmap>),
 }
@@ -161,6 +162,17 @@ pub(crate) fn write_typed_chunk_into_index(
             )?;
             is_merged_database = true;
         }
+        TypedChunk::FieldIdFacetIsNullDocids(facet_id_is_null_docids) => {
+            append_entries_into_database(
+                facet_id_is_null_docids,
+                &index.facet_id_is_null_docids,
+                wtxn,
+                index_is_empty,
+                |value, _buffer| Ok(value),
+                merge_cbo_roaring_bitmaps,
+            )?;
+            is_merged_database = true;
+        }
         TypedChunk::WordPairProximityDocids(word_pair_proximity_docids_iter) => {
             append_entries_into_database(
                 word_pair_proximity_docids_iter,