Remove the experimental implementation of MSC3772. (#14094)

MSC3772 has been abandoned.

synapse/storage/databases/main/relations.py

@@ -776,59 +776,6 @@ class RelationsWorkerStore(SQLBaseStore):
             "get_if_user_has_annotated_event", _get_if_user_has_annotated_event
         )
 
-    @cached(iterable=True)
-    async def get_mutual_event_relations_for_rel_type(
-        self, event_id: str, relation_type: str
-    ) -> Set[Tuple[str, str]]:
-        raise NotImplementedError()
-
-    @cachedList(
-        cached_method_name="get_mutual_event_relations_for_rel_type",
-        list_name="relation_types",
-    )
-    async def get_mutual_event_relations(
-        self, event_id: str, relation_types: Collection[str]
-    ) -> Dict[str, Set[Tuple[str, str]]]:
-        """
-        Fetch event metadata for events which related to the same event as the given event.
-
-        If the given event has no relation information, returns an empty dictionary.
-
-        Args:
-            event_id: The event ID which is targeted by relations.
-            relation_types: The relation types to check for mutual relations.
-
-        Returns:
-            A dictionary of relation type to:
-                A set of tuples of:
-                    The sender
-                    The event type
-        """
-        rel_type_sql, rel_type_args = make_in_list_sql_clause(
-            self.database_engine, "relation_type", relation_types
-        )
-
-        sql = f"""
-            SELECT DISTINCT relation_type, sender, type FROM event_relations
-            INNER JOIN events USING (event_id)
-            WHERE relates_to_id = ? AND {rel_type_sql}
-        """
-
-        def _get_event_relations(
-            txn: LoggingTransaction,
-        ) -> Dict[str, Set[Tuple[str, str]]]:
-            txn.execute(sql, [event_id] + rel_type_args)
-            result: Dict[str, Set[Tuple[str, str]]] = {
-                rel_type: set() for rel_type in relation_types
-            }
-            for rel_type, sender, type in txn.fetchall():
-                result[rel_type].add((sender, type))
-            return result
-
-        return await self.db_pool.runInteraction(
-            "get_event_relations", _get_event_relations
-        )
-
     @cached()
     async def get_thread_id(self, event_id: str) -> Optional[str]:
         """