Add index to help delete old push actions

changelog.d/13141.bugfix

@@ -0,0 +1 @@
+Fix DB performance when deleting old push notifications. Introduced in v1.62.0rc1.

synapse/storage/databases/main/event_push_actions.py

@@ -1189,6 +1189,16 @@ def __init__(
             where_clause="highlight=1",
         )
 
+        # Add index to make deleting old push actions faster.
+        self.db_pool.updates.register_background_index_update(
+            "event_push_actions_stream_highlight_index",
+            index_name="event_push_actions_stream_highlight_index",
+            table="event_push_actions",
+            columns=["highlight", "stream_ordering"],
+            where_clause="highlight=0",
+            psql_only=True,
+        )
+
     async def get_push_actions_for_user(
         self,
         user_id: str,

synapse/storage/schema/main/delta/72/02event_push_actions_index.sql

@@ -0,0 +1,19 @@
+/* Copyright 2022 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- Add an index to `event_push_actions` to make deleting old non-highlight push
+-- actions faster.
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (7002, 'event_push_actions_stream_highlight_index', '{}');