Speed up calculating push actions in large rooms

changelog.d/13973.misc

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

synapse/push/bulk_push_rule_evaluator.py

@@ -303,20 +303,10 @@ async def action_for_event_by_user(
  event.room_id, users
  )
 
- # 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
- uids_with_visibility = await filter_event_for_clients_with_state(
- self.store, users, event, context
- )
-
  for uid, rules in rules_by_user.items():
  if event.sender == uid:
  continue
 
- if uid not in uids_with_visibility:
- continue
-
  display_name = None
  profile = profiles.get(uid)
  if profile:
@@ -342,6 +332,21 @@ async def action_for_event_by_user(
  # Push rules say we should notify the user of this event
  actions_by_user[uid] = actions
 
+ # 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
+ #
+ # We do this *after* calculating the push actions as a) its unlikely
+ # that we'll filter anyone out and b) for large rooms its likely that
+ # most users will have push disabled and so the set of users to check is
+ # much smaller.
+ uids_with_visibility = await filter_event_for_clients_with_state(
+ self.store, actions_by_user.keys(), event, context
+ )
+
+ for user_id in set(uids_with_visibility).difference(uids_with_visibility):
+ actions_by_user.pop(user_id, None)
+
  # Mark in the DB staging area the push actions for users who should be
  # notified for this event. (This will then get handled when we persist
  # the event)