add rename_table fn and more data for index_stats to return (#1234)

1. added rename_table fn to enable dashboard to rename a table
2. added index_type and distance_type (for vector index) to index_stats
so that more detailed data can be shown on the table page.

rust/lancedb/src/index/vector.rs

@@ -46,10 +46,18 @@ impl VectorIndex {
     }
 }
 
+#[derive(Debug, Deserialize)]
+pub struct VectorIndexMetadata {
+    pub metric_type: String,
+    pub index_type: String,
+}
+
 #[derive(Debug, Deserialize)]
 pub struct VectorIndexStatistics {
     pub num_indexed_rows: usize,
     pub num_unindexed_rows: usize,
+    pub index_type: String,
+    pub indices: Vec<VectorIndexMetadata>,
 }
 
 /// Builder for an IVF PQ index.

rust/lancedb/src/table.rs

@@ -1061,6 +1061,26 @@ impl NativeTable {
         }
     }
 
+    pub async fn get_index_type(&self, index_uuid: &str) -> Result<Option<String>> {
+        match self.load_index_stats(index_uuid).await? {
+            Some(stats) => Ok(Some(stats.index_type)),
+            None => Ok(None),
+        }
+    }
+
+    pub async fn get_distance_type(&self, index_uuid: &str) -> Result<Option<String>> {
+        match self.load_index_stats(index_uuid).await? {
+            Some(stats) => Ok(Some(
+                stats
+                    .indices
+                    .iter()
+                    .map(|i| i.metric_type.clone())
+                    .collect(),
+            )),
+            None => Ok(None),
+        }
+    }
+
     pub async fn load_indices(&self) -> Result<Vec<VectorIndex>> {
         let dataset = self.dataset.get().await?;
         let (indices, mf) = futures::try_join!(dataset.load_indices(), dataset.latest_manifest())?;