feat: support IVF_FLAT, binary vectors and hamming distance (#1955)

binary vectors and hamming distance can work on only IVF_FLAT, so
introduce them all in this PR.

---------

Signed-off-by: BubbleCal <bubble-cal@outlook.com>

python/src/index.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use lancedb::index::vector::IvfFlatIndexBuilder;
 use lancedb::index::{
     scalar::{BTreeIndexBuilder, FtsIndexBuilder, TokenizerConfig},
     vector::{IvfHnswPqIndexBuilder, IvfHnswSqIndexBuilder, IvfPqIndexBuilder},
@@ -59,6 +60,18 @@ pub fn extract_index_params(source: &Option<Bound<'_, PyAny>>) -> PyResult<Lance
                 opts.tokenizer_configs = inner_opts;
                 Ok(LanceDbIndex::FTS(opts))
             },
+            "IvfFlat" => {
+                let params = source.extract::<IvfFlatParams>()?;
+                let distance_type = parse_distance_type(params.distance_type)?;
+                let mut ivf_flat_builder = IvfFlatIndexBuilder::default()
+                    .distance_type(distance_type)
+                    .max_iterations(params.max_iterations)
+                    .sample_rate(params.sample_rate);
+                if let Some(num_partitions) = params.num_partitions {
+                    ivf_flat_builder = ivf_flat_builder.num_partitions(num_partitions);
+                }
+                Ok(LanceDbIndex::IvfFlat(ivf_flat_builder))
+            },
             "IvfPq" => {
                 let params = source.extract::<IvfPqParams>()?;
                 let distance_type = parse_distance_type(params.distance_type)?;
@@ -129,6 +142,14 @@ struct FtsParams {
     ascii_folding: bool,
 }
 
+#[derive(FromPyObject)]
+struct IvfFlatParams {
+    distance_type: String,
+    num_partitions: Option<u32>,
+    max_iterations: u32,
+    sample_rate: u32,
+}
+
 #[derive(FromPyObject)]
 struct IvfPqParams {
     distance_type: String,

python/src/util.rs

@@ -43,8 +43,9 @@ pub fn parse_distance_type(distance_type: impl AsRef<str>) -> PyResult<DistanceT
         "l2" => Ok(DistanceType::L2),
         "cosine" => Ok(DistanceType::Cosine),
         "dot" => Ok(DistanceType::Dot),
+        "hamming" => Ok(DistanceType::Hamming),
         _ => Err(PyValueError::new_err(format!(
-            "Invalid distance type '{}'.  Must be one of l2, cosine, or dot",
+            "Invalid distance type '{}'.  Must be one of l2, cosine, dot, or hamming",
             distance_type.as_ref()
         ))),
     }