Review comments

synapse/storage/databases/main/group_server.py

@@ -45,7 +45,7 @@ def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"
             update_name="local_group_updates_index",
             index_name="local_group_updates_stream_id_index",
             table="local_group_updates",
-            columns=("stream_id"),
+            columns=("stream_id",),
             unique=True,
         )
         super().__init__(database, db_conn, hs)

synapse/storage/schema/main/delta/65/03_local_group_updates.sql

@@ -13,6 +13,6 @@
  * limitations under the License.
  */
 
--- Check old events for thread relations.
+-- Check index on `local_group_updates.stream_id`.
 INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
   (6503, 'local_group_updates_index', '{}');