Revert "Look for bump stamp in the room timeline"

This reverts commit a3c49565.

synapse/handlers/sliding_sync/__init__.py

@@ -1045,36 +1045,24 @@ class SlidingSyncHandler:
 
         # Figure out the last bump event in the room if we're in the room.
         if room_membership_for_user_at_to_token.membership == Membership.JOIN:
-            new_bump_stamp: Optional[int] = None
-
-            # First check the timeline events we're returning to see if one of
-            # those matches. We iterate backwards and take the stream ordering
-            # of the first event that matches the bump event types.
-            for timeline_event in reversed(timeline_events):
-                if timeline_event.type in SLIDING_SYNC_DEFAULT_BUMP_EVENT_TYPES:
-                    new_bump_stamp = timeline_event.internal_metadata.stream_ordering
-                    break
-            else:
-                # If not then we query the DB for it.
-                last_bump_event_result = (
-                    await self.store.get_last_event_pos_in_room_before_stream_ordering(
-                        room_id,
-                        to_token.room_key,
-                        event_types=SLIDING_SYNC_DEFAULT_BUMP_EVENT_TYPES,
-                    )
+            last_bump_event_result = (
+                await self.store.get_last_event_pos_in_room_before_stream_ordering(
+                    room_id,
+                    to_token.room_key,
+                    event_types=SLIDING_SYNC_DEFAULT_BUMP_EVENT_TYPES,
                 )
-                if last_bump_event_result is not None:
-                    _, new_bump_event_pos = last_bump_event_result
-                    new_bump_stamp = new_bump_event_pos.stream
+            )
+
+            # But if we found a bump event, use that instead
+            if last_bump_event_result is not None:
+                _, new_bump_event_pos = last_bump_event_result
 
-            # If we found a bump event, use that instead
-            if new_bump_stamp is not None:
                 # If we've just joined a remote room, then the last bump event may
                 # have been backfilled (and so have a negative stream ordering).
                 # These negative stream orderings can't sensibly be compared, so
                 # instead we use the membership event position.
-                if new_bump_stamp > 0:
-                    bump_stamp = new_bump_stamp
+                if new_bump_event_pos.stream > 0:
+                    bump_stamp = new_bump_event_pos.stream
 
         unstable_expanded_timeline = False
         prev_room_sync_config = previous_connection_state.room_configs.get(room_id)