Optimize cbo roaring bitmaps merge

milli/src/heed_codec/roaring_bitmap/cbo_roaring_bitmap_codec.rs

@@ -52,6 +52,46 @@ impl CboRoaringBitmapCodec {
             RoaringBitmap::deserialize_from(bytes)
         }
     }
+
+    /// Merge serialized CboRoaringBitmaps in a buffer.
+    ///
+    /// if the merged values len is under the threshold,
+    /// values are directly serialized in the buffer;
+    /// else a RoaringBitmap is created from the values and is serialized in the buffer.
+    pub fn merge_into(slices: &[Cow<[u8]>], buffer: &mut Vec<u8>) -> io::Result<()> {
+        let mut roaring = RoaringBitmap::new();
+        let mut vec = Vec::new();
+
+        for bytes in slices {
+            if bytes.len() <= THRESHOLD * size_of::<u32>() {
+                let mut reader = bytes.as_ref();
+                while let Ok(integer) = reader.read_u32::<NativeEndian>() {
+                    vec.push(integer);
+                }
+            } else {
+                roaring |= RoaringBitmap::deserialize_from(bytes.as_ref())?;
+            }
+        }
+
+        if roaring.is_empty() {
+            vec.sort_unstable();
+            vec.dedup();
+
+            if vec.len() <= THRESHOLD {
+                for integer in vec {
+                    buffer.extend_from_slice(&integer.to_ne_bytes());
+                }
+            } else {
+                let roaring = RoaringBitmap::from_sorted_iter(vec.into_iter());
+                roaring.serialize_into(buffer)?;
+            }
+        } else {
+            roaring.extend(vec);
+            roaring.serialize_into(buffer)?;
+        }
+
+        Ok(())
+    }
 }
 
 impl heed::BytesDecode<'_> for CboRoaringBitmapCodec {
@@ -106,4 +146,40 @@ mod tests {
 
         assert!(roaring_size > bo_size);
     }
+
+    #[test]
+    fn merge_cbo_roaring_bitmaps() {
+        let mut buffer = Vec::new();
+
+        let small_data = vec![
+            RoaringBitmap::from_sorted_iter(1..4),
+            RoaringBitmap::from_sorted_iter(2..5),
+            RoaringBitmap::from_sorted_iter(4..6),
+            RoaringBitmap::from_sorted_iter(1..3),
+        ];
+
+        let small_data: Vec<_> =
+            small_data.iter().map(|b| CboRoaringBitmapCodec::bytes_encode(b).unwrap()).collect();
+        CboRoaringBitmapCodec::merge_into(small_data.as_slice(), &mut buffer).unwrap();
+        let bitmap = CboRoaringBitmapCodec::deserialize_from(&buffer).unwrap();
+        let expected = RoaringBitmap::from_sorted_iter(1..6);
+        assert_eq!(bitmap, expected);
+
+        let medium_data = vec![
+            RoaringBitmap::from_sorted_iter(1..4),
+            RoaringBitmap::from_sorted_iter(2..5),
+            RoaringBitmap::from_sorted_iter(4..8),
+            RoaringBitmap::from_sorted_iter(0..3),
+            RoaringBitmap::from_sorted_iter(7..23),
+        ];
+
+        let medium_data: Vec<_> =
+            medium_data.iter().map(|b| CboRoaringBitmapCodec::bytes_encode(b).unwrap()).collect();
+        buffer.clear();
+        CboRoaringBitmapCodec::merge_into(medium_data.as_slice(), &mut buffer).unwrap();
+
+        let bitmap = CboRoaringBitmapCodec::deserialize_from(&buffer).unwrap();
+        let expected = RoaringBitmap::from_sorted_iter(0..23);
+        assert_eq!(bitmap, expected);
+    }
 }

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

@@ -120,52 +120,11 @@ pub fn merge_cbo_roaring_bitmaps<'a>(
     _key: &[u8],
     values: &[Cow<'a, [u8]>],
 ) -> Result<Cow<'a, [u8]>> {
-    match values.split_first().unwrap() {
+    if values.len() == 1 {
-        (head, []) => Ok(head.clone()),
+        Ok(values[0].clone())
-        (head, tail) => {
+    } else {
-            let mut head = CboRoaringBitmapCodec::deserialize_from(&head[..])?;
-
-            for value in tail {
-                head |= CboRoaringBitmapCodec::deserialize_from(&value[..])?;
-            }
-
         let mut vec = Vec::new();
-            CboRoaringBitmapCodec::serialize_into(&head, &mut vec);
+        CboRoaringBitmapCodec::merge_into(values, &mut vec)?;
         Ok(Cow::from(vec))
     }
-    }
 }
-
-// /// Uses the FacetStringLevelZeroValueCodec to merge the values.
-// pub fn tuple_string_cbo_roaring_bitmap_merge<'a>(
-//     _key: &[u8],
-//     values: &[Cow<[u8]>],
-// ) -> Result<Cow<'a, [u8]>> {
-//     let (head, tail) = values.split_first().unwrap();
-//     let (head_string, mut head_rb) = FacetStringLevelZeroValueCodec::bytes_decode(&head[..])
-//         .ok_or(SerializationError::Decoding { db_name: None })?;
-
-//     for value in tail {
-//         let (_string, rb) = FacetStringLevelZeroValueCodec::bytes_decode(&value[..])
-//             .ok_or(SerializationError::Decoding { db_name: None })?;
-//         head_rb |= rb;
-//     }
-
-//     FacetStringLevelZeroValueCodec::bytes_encode(&(head_string, head_rb))
-//         .map(|cow| cow.into_owned())
-//         .ok_or(SerializationError::Encoding { db_name: None })
-//         .map_err(Into::into)
-// }
-
-// pub fn cbo_roaring_bitmap_merge<'a>(_key: &[u8], values: &[Cow<[u8]>]) -> Result<Cow<'a, [u8]>> {
-//     let (head, tail) = values.split_first().unwrap();
-//     let mut head = CboRoaringBitmapCodec::deserialize_from(&head[..])?;
-
-//     for value in tail {
-//         head |= CboRoaringBitmapCodec::deserialize_from(&value[..])?;
-//     }
-
-//     let mut vec = Vec::new();
-//     CboRoaringBitmapCodec::serialize_into(&head, &mut vec);
-//     Ok(vec)
-// }

milli/src/update/index_documents/typed_chunk.rs

@@ -188,15 +188,22 @@ fn merge_roaring_bitmaps(new_value: &[u8], db_value: &[u8], buffer: &mut Vec<u8>
     Ok(serialize_roaring_bitmap(&value, buffer)?)
 }
 
+use std::borrow::Cow;
+
 fn merge_cbo_roaring_bitmaps(
     new_value: &[u8],
     db_value: &[u8],
     buffer: &mut Vec<u8>,
 ) -> Result<()> {
-    let new_value = CboRoaringBitmapCodec::deserialize_from(new_value)?;
+    Ok(CboRoaringBitmapCodec::merge_into(
-    let db_value = CboRoaringBitmapCodec::deserialize_from(db_value)?;
+        &[Cow::Borrowed(db_value), Cow::Borrowed(new_value)],
-    let value = new_value | db_value;
+        buffer,
-    Ok(CboRoaringBitmapCodec::serialize_into(&value, buffer))
+    )?)
+
+    // let new_value = CboRoaringBitmapCodec::deserialize_from(new_value)?;
+    // let db_value = CboRoaringBitmapCodec::deserialize_from(db_value)?;
+    // let value = new_value | db_value;
+    // Ok(CboRoaringBitmapCodec::serialize_into(&value, buffer))
 }
 
 /// Write provided entries in database using serialize_value function.