Sliding sync: don't fetch room summary for named rooms. (#17683)

For rooms with a name we can skip fetching a full room summary, as we
don't need to calculate heroes, and instead just fetch the room counts
directly.

This also changes things to not return counts and heroes for non-joined
rooms. For left/banned rooms we were returning zero values anyway, and
for invite/knock rooms we don't really want to leak such information
(even if some of is included in the stripped state).

1 files changed, 8 insertions, 0 deletions

diff --git a/synapse/storage/databases/main/state.py b/synapse/storage/databases/main/state.py

index c5caaf56b0..ca31122ad3 100644
--- a/synapse/storage/databases/main/state.py
+++ b/synapse/storage/databases/main/state.py
@@ -736,6 +736,7 @@ class MainStateBackgroundUpdateStore(RoomMemberWorkerStore):
     CURRENT_STATE_INDEX_UPDATE_NAME = "current_state_members_idx"
     EVENT_STATE_GROUP_INDEX_UPDATE_NAME = "event_to_state_groups_sg_index"
     DELETE_CURRENT_STATE_UPDATE_NAME = "delete_old_current_state_events"
+    MEMBERS_CURRENT_STATE_UPDATE_NAME = "current_state_events_members_room_index"
 
     def __init__(
         self,
@@ -764,6 +765,13 @@ class MainStateBackgroundUpdateStore(RoomMemberWorkerStore):
             self.DELETE_CURRENT_STATE_UPDATE_NAME,
             self._background_remove_left_rooms,
         )
+        self.db_pool.updates.register_background_index_update(
+            self.MEMBERS_CURRENT_STATE_UPDATE_NAME,
+            index_name="current_state_events_members_room_index",
+            table="current_state_events",
+            columns=["room_id", "membership"],
+            where_clause="type='m.room.member'",
+        )
 
     async def _background_remove_left_rooms(
         self, progress: JsonDict, batch_size: int