Fix alias query.

synapse/storage/directory.py

@@ -141,20 +141,19 @@ class DirectoryStore(SQLBaseStore):
         Returns:
             A list of RoomAliasMappings.
         """
-        results = self._simple_select_list(
-            "room_aliases",
-            None,
-            ["room_alias", "room_id"]
+        results = yield self._execute_and_decode(
+            "SELECT room_id, room_alias FROM room_aliases"
         )
+
         # TODO(kegan): It feels wrong to be specifying no servers here, but
         # equally this function isn't required to obtain all servers so
         # retrieving them "just for the sake of it" also seems wrong, but we
         # want to conform to passing Objects around and not dicts..
-        return [
+        defer.returnValue([
             RoomAliasMapping(
                 room_id=r["room_id"], room_alias=r["room_alias"], servers=""
             ) for r in results
-        ]
+        ])
 
 
     def get_aliases_for_room(self, room_id):