def _collection_length(self, final_set):
        conn = self.cls.get_connection()
        if self._has_sortedsets:
            return conn.zcard(final_set)
        elif self.stored_key and not self._lazy_collection['sets']\
                and len(self._lazy_collection['intersects']) == 1:
            return conn.llen(final_set)
        return super(ExtendedCollectionManager, self)._collection_length(final_set)