community[patch]: Update lancedb.py (#21192)

very minor update in LanceDB integration, 'metric' argument was missing.

libs/community/langchain_community/vectorstores/lancedb.py

@@ -151,10 +151,30 @@ class LanceDB(VectorStore):
             self._connection.create_table(self._table_name, data=docs)
         return ids
 
-    def get_table(self, name: Optional[str] = None) -> Any:
+    def get_table(
+        self, name: Optional[str] = None, set_default: Optional[bool] = False
+    ) -> Any:
+        """
+        Fetches a table object from the database.
+
+        Args:
+            name (str, optional): The name of the table to fetch. Defaults to None
+                                    and fetches current table object.
+            set_default (bool, optional): Sets fetched table as the default table.
+                                        Defaults to False.
+
+        Returns:
+            Any: The fetched table object.
+
+        Raises:
+            ValueError: If the specified table is not found in the database.
+
+        """
         if name is not None:
             try:
-                self._connection.open_table(name)
+                if set_default:
+                    self._table_name = name
+                    return self._connection.open_table(name)
             except Exception:
                 raise ValueError(f"Table {name} not found in the database")
         else:
@@ -167,6 +187,7 @@ class LanceDB(VectorStore):
         num_partitions: Optional[int] = 256,
         num_sub_vectors: Optional[int] = 96,
         index_cache_size: Optional[int] = None,
+        metric: Optional[str] = "L2",
     ) -> None:
         """
         Create a scalar(for non-vector cols) or a vector index on a table.
@@ -181,15 +202,18 @@ class LanceDB(VectorStore):
         Returns:
             None
         """
+        tbl = self.get_table()
+
         if vector_col:
-            self._connection.create_index(
+            tbl.create_index(
+                metric=metric,
                 vector_column_name=vector_col,
                 num_partitions=num_partitions,
                 num_sub_vectors=num_sub_vectors,
                 index_cache_size=index_cache_size,
             )
         elif col_name:
-            self._connection.create_scalar_index(col_name)
+            tbl.create_scalar_index(col_name)
         else:
             raise ValueError("Provide either vector_col or col_name")