Add debug logs on incremental facet indexing

milli/src/update/facet/incremental.rs

@@ -66,6 +66,7 @@ impl FacetsUpdateIncremental {
     #[logging_timer::time("FacetsUpdateIncremental::{}")]
     pub fn execute(self, wtxn: &mut RwTxn) -> crate::Result<()> {
         let mut iter = self.delta_data.into_stream_merger_iter()?;
+        let mut current_field_id = None;
 
         while let Some((key, value)) = iter.next()? {
             if !valid_lmdb_key(key) {
@@ -75,6 +76,22 @@ impl FacetsUpdateIncremental {
             let key = FacetGroupKeyCodec::<BytesRefCodec>::bytes_decode(key)
                 .map_err(heed::Error::Encoding)?;
             let value = KvReader::new(value);
+
+            if current_field_id.map_or(true, |fid| fid != key.field_id) {
+                if let Some(fid) = current_field_id {
+                    let highest_level = get_highest_level(wtxn, self.inner.db, fid)?;
+                    let field_id_prefix = &fid.to_be_bytes();
+                    let line_count = self
+                        .inner
+                        .db
+                        .remap_types::<Bytes, DecodeIgnore>()
+                        .prefix_iter(wtxn, field_id_prefix)?
+                        .count();
+                    log::debug!("field_id {fid} contains {line_count} keys and the highest level is {highest_level}");
+                }
+
+                current_field_id = Some(key.field_id)
+            }
             let docids_to_delete = value
                 .get(DelAdd::Deletion)
                 .map(CboRoaringBitmapCodec::bytes_decode)

milli/src/update/facet/mod.rs

@@ -150,6 +150,7 @@ impl<'i> FacetsUpdate<'i> {
 
         // See self::comparison_bench::benchmark_facet_indexing
         if self.data_size >= (self.database.len(wtxn)? / 50) {
+            debug!("Incremental indexing of {} keys", self.data_size);
             let field_ids =
                 self.index.faceted_fields_ids(wtxn)?.iter().copied().collect::<Vec<_>>();
             let bulk_update = FacetsUpdateBulk::new(