Make get_room_version use cached get_room_version_id.

changelog.d/11808.misc

@@ -0,0 +1 @@
+Make method `get_room_version` use cached `get_room_version_id`.

synapse/storage/databases/main/state.py

@@ -62,11 +62,8 @@ async def get_room_version(self, room_id: str) -> RoomVersion:
                 Typically this happens if support for the room's version has been
                 removed from Synapse.
         """
-        return await self.db_pool.runInteraction(
-            "get_room_version_txn",
-            self.get_room_version_txn,
-            room_id,
-        )
+        room_version_id = await self.get_room_version_id(room_id)
+        return self.__retrieve_and_check_room_version(room_id, room_version_id)
 
     def get_room_version_txn(
         self, txn: LoggingTransaction, room_id: str
@@ -82,14 +79,17 @@ def get_room_version_txn(
                 removed from Synapse.
         """
         room_version_id = self.get_room_version_id_txn(txn, room_id)
-        v = KNOWN_ROOM_VERSIONS.get(room_version_id)
+        return self.__retrieve_and_check_room_version(room_id, room_version_id)
 
+    def __retrieve_and_check_room_version(
+        self, room_id: str, room_version_id: str
+    ) -> RoomVersion:
+        v = KNOWN_ROOM_VERSIONS.get(room_version_id)
         if not v:
             raise UnsupportedRoomVersionError(
                 "Room %s uses a room version %s which is no longer supported"
                 % (room_id, room_version_id)
             )
-
         return v
 
     @cached(max_entries=10000)