feat: remote index stats (#1702)

BREAKING CHANGE: the return value of `index_stats` method has changed
and all `index_stats` APIs now take index name instead of UUID. Also
several deprecated index statistics methods were removed.

* Removes deprecated methods for individual index statistics
* Aligns public `IndexStatistics` struct with API response from LanceDB
Cloud.
* Implements `index_stats` for remote Rust SDK and Python async API.

nodejs/__test__/table.test.ts

@@ -479,6 +479,9 @@ describe("When creating an index", () => {
     expect(stats).toBeDefined();
     expect(stats?.numIndexedRows).toEqual(300);
     expect(stats?.numUnindexedRows).toEqual(0);
+    expect(stats?.distanceType).toBeUndefined();
+    expect(stats?.indexType).toEqual("BTREE");
+    expect(stats?.numIndices).toEqual(1);
   });
 
   test("when getting stats on non-existent index", async () => {

nodejs/lancedb/index.ts

@@ -32,7 +32,6 @@ export {
   ColumnAlteration,
   ConnectionOptions,
   IndexStatistics,
-  IndexMetadata,
   IndexConfig,
 } from "./native.js";
 

nodejs/src/table.rs

@@ -337,7 +337,7 @@ impl Table {
 
     #[napi(catch_unwind)]
     pub async fn index_stats(&self, index_name: String) -> napi::Result<Option<IndexStatistics>> {
-        let tbl = self.inner_ref()?.as_native().unwrap();
+        let tbl = self.inner_ref()?;
         let stats = tbl.index_stats(&index_name).await.default_error()?;
         Ok(stats.map(IndexStatistics::from))
     }
@@ -480,32 +480,22 @@ pub struct IndexStatistics {
     /// The number of rows not indexed
     pub num_unindexed_rows: f64,
     /// The type of the index
-    pub index_type: Option<String>,
-    /// The metadata for each index
-    pub indices: Vec<IndexMetadata>,
+    pub index_type: String,
+    /// The type of the distance function used by the index. This is only
+    /// present for vector indices. Scalar and full text search indices do
+    /// not have a distance function.
+    pub distance_type: Option<String>,
+    /// The number of parts this index is split into.
+    pub num_indices: Option<u32>,
 }
 impl From<lancedb::index::IndexStatistics> for IndexStatistics {
     fn from(value: lancedb::index::IndexStatistics) -> Self {
         Self {
             num_indexed_rows: value.num_indexed_rows as f64,
             num_unindexed_rows: value.num_unindexed_rows as f64,
-            index_type: value.index_type.map(|t| format!("{:?}", t)),
-            indices: value.indices.into_iter().map(Into::into).collect(),
-        }
-    }
-}
-
-#[napi(object)]
-pub struct IndexMetadata {
-    pub metric_type: Option<String>,
-    pub index_type: Option<String>,
-}
-
-impl From<lancedb::index::IndexMetadata> for IndexMetadata {
-    fn from(value: lancedb::index::IndexMetadata) -> Self {
-        Self {
-            metric_type: value.metric_type,
-            index_type: value.index_type,
+            index_type: value.index_type.to_string(),
+            distance_type: value.distance_type.map(|d| d.to_string()),
+            num_indices: value.num_indices,
         }
     }
 }