Skip filtering during push if there are no push actions

changelog.d/13992.misc

@@ -0,0 +1 @@
+Speed up calculating push actions in large rooms.

synapse/push/bulk_push_rule_evaluator.py

@@ -332,6 +332,11 @@ async def action_for_event_by_user(
                 # Push rules say we should notify the user of this event
                 actions_by_user[uid] = actions
 
+        # If there aren't any actions then we can skip the rest of the
+        # processing.
+        if not actions_by_user:
+            return
+
         # This is a check for the case where user joins a room without being
         # allowed to see history, and then the server receives a delayed event
         # from before the user joined, which they should not be pushed for

synapse/visibility.py

@@ -162,6 +162,10 @@ async def filter_event_for_clients_with_state(
     if event.internal_metadata.is_soft_failed():
         return []
 
+    # Fast path if we don't have any user IDs to check.
+    if not user_ids:
+        return ()
+
     # Make a set for all user IDs that haven't been filtered out by a check.
     allowed_user_ids = set(user_ids)
 

tests/rest/client/test_rooms.py

@@ -710,7 +710,7 @@ def test_post_room_no_keys(self) -> None:
         self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
         self.assertTrue("room_id" in channel.json_body)
         assert channel.resource_usage is not None
-        self.assertEqual(35, channel.resource_usage.db_txn_count)
+        self.assertEqual(34, channel.resource_usage.db_txn_count)
 
     def test_post_room_initial_state(self) -> None:
         # POST with initial_state config key, expect new room id
@@ -723,7 +723,7 @@ def test_post_room_initial_state(self) -> None:
         self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
         self.assertTrue("room_id" in channel.json_body)
         assert channel.resource_usage is not None
-        self.assertEqual(38, channel.resource_usage.db_txn_count)
+        self.assertEqual(37, channel.resource_usage.db_txn_count)
 
     def test_post_room_visibility_key(self) -> None:
         # POST with visibility config key, expect new room id