Don't recreate so many sets

1 files changed, 6 insertions, 5 deletions

diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 545d3d3a99..5f044a3f18 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -274,24 +274,25 @@ class RoomMemberStore(SQLBaseStore):
 
         return rows
 
-    @cached(max_entries=500000, iterable=True)
+    @cachedInlineCallbacks(max_entries=500000, iterable=True)
     def get_rooms_for_user(self, user_id):
-        return self.get_rooms_for_user_where_membership_is(
+        rooms = yield self.get_rooms_for_user_where_membership_is(
             user_id, membership_list=[Membership.JOIN],
         )
+        defer.returnValue(frozenset(r.room_id for r in rooms))
 
     @cachedInlineCallbacks(max_entries=500000, cache_context=True, iterable=True)
     def get_users_who_share_room_with_user(self, user_id, cache_context):
         """Returns the set of users who share a room with `user_id`
         """
-        rooms = yield self.get_rooms_for_user(
+        room_ids = yield self.get_rooms_for_user(
             user_id, on_invalidate=cache_context.invalidate,
         )
 
         user_who_share_room = set()
-        for room in rooms:
+        for room_id in room_ids:
             user_ids = yield self.get_users_in_room(
-                room.room_id, on_invalidate=cache_context.invalidate,
+                room_id, on_invalidate=cache_context.invalidate,
             )
             user_who_share_room.update(user_ids)