Skip unused calculations in sync handler. (#14908)

If a sync request does not need to calculate per-room entries &
is not generating presence & is not generating device list data
(e.g. during initial sync) avoid the expensive calculation of room
specific data.

This is a micro-optimisation for clients syncing simply to receive
to-device information.

1 files changed, 3 insertions, 0 deletions

diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index 4cf8f0cc8e..2b5af264b4 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -283,6 +283,9 @@ class FilterCollection:
             await self._room_filter.filter(events)
         )
 
+    def blocks_all_rooms(self) -> bool:
+        return self._room_filter.filters_all_rooms()
+
     def blocks_all_presence(self) -> bool:
         return (
             self._presence_filter.filters_all_types()