Use get_room_events_stream to get changes to the rooms if the number of changes is small

synapse/handlers/sync.py

@@ -216,19 +216,53 @@ class SyncHandler(BaseHandler):
         typing_by_room = {event["room_id"]: event for event in typing}
         logger.debug("Typing %r", typing_by_room)
 
-        room_list = yield self.store.get_rooms_for_user_where_membership_is(
-            user_id=sync_config.user.to_string(),
-            membership_list=[Membership.INVITE, Membership.JOIN]
-        )
+        rm_handler = self.hs.get_handlers().room_member_handler
+        room_ids = yield rm_handler.get_rooms_for_user(sync_config.user)
 
         # TODO (mjark): Does public mean "published"?
         published_rooms = yield self.store.get_rooms(is_public=True)
         published_room_ids = set(r["room_id"] for r in published_rooms)
 
+        room_events, _ = yield self.store.get_room_events_stream(
+            sync_config.user.to_string(),
+            from_key=since_token.room_key,
+            to_key=now_token.room_key,
+            room_id=None,
+            limit=sync_config.limit + 1,
+        )
+
         rooms = []
-        for event in room_list:
+        if len(room_events) <= sync_config.limit:
+            # There is no gap in any of the rooms. Therefore we can just
+            # partition the new events by room and return them.
+            events_by_room_id = {}
+            for event in room_events:
+                events_by_room_id.setdefault(event.room_id, []).append(event)
+
+            for room_id in room_ids:
+                recents = events_by_room_id.get(room_id, [])
+                state = [event for event in recents if event.is_state()]
+                if recents:
+                    prev_batch = now_token.copy_and_replace(
+                        "room_key", recents[0].internal_metadata.before
+                    )
+                else:
+                    prev_batch = now_token
+                room_sync = RoomSyncResult(
+                    room_id=room_id,
+                    published=room_id in published_room_ids,
+                    events=recents,
+                    prev_batch=prev_batch,
+                    state=state,
+                    limited=False,
+                    typing=typing_by_room.get(room_id, None)
+                )
+                if room_sync is not None:
+                    rooms.append(room_sync)
+        else:
+            for room_id in room_ids:
                 room_sync = yield self.incremental_sync_with_gap_for_room(
-                event.room_id, sync_config, since_token, now_token,
+                    room_id, sync_config, since_token, now_token,
                     published_room_ids, typing_by_room
                 )
                 if room_sync:

synapse/storage/stream.py

@@ -181,6 +181,13 @@ class StreamStore(SQLBaseStore):
                 get_prev_content=True
             )
 
+            for event, row in zip(ret, rows):
+                stream = row["stream_ordering"]
+                topo = event.depth
+                internal = event.internal_metadata
+                internal.before = str(_StreamToken(topo, stream - 1))
+                internal.after = str(_StreamToken(topo, stream))
+
             if rows:
                 key = "s%d" % max([r["stream_ordering"] for r in rows])
             else: