Add type hints to synapse/storage/databases/main (#11984)

synapse/storage/databases/main/purge_events.py

@@ -13,9 +13,10 @@
 # limitations under the License.
 
 import logging
-from typing import Any, List, Set, Tuple
+from typing import Any, List, Set, Tuple, cast
 
 from synapse.api.errors import SynapseError
+from synapse.storage.database import LoggingTransaction
 from synapse.storage.databases.main import CacheInvalidationWorkerStore
 from synapse.storage.databases.main.state import StateGroupWorkerStore
 from synapse.types import RoomStreamToken
@@ -55,7 +56,11 @@ class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
         )
 
     def _purge_history_txn(
-        self, txn, room_id: str, token: RoomStreamToken, delete_local_events: bool
+        self,
+        txn: LoggingTransaction,
+        room_id: str,
+        token: RoomStreamToken,
+        delete_local_events: bool,
     ) -> Set[int]:
         # Tables that should be pruned:
         #     event_auth
@@ -273,7 +278,7 @@ class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
         """,
             (room_id,),
         )
-        (min_depth,) = txn.fetchone()
+        (min_depth,) = cast(Tuple[int], txn.fetchone())
 
         logger.info("[purge] updating room_depth to %d", min_depth)
 
@@ -318,7 +323,7 @@ class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
             "purge_room", self._purge_room_txn, room_id
         )
 
-    def _purge_room_txn(self, txn, room_id: str) -> List[int]:
+    def _purge_room_txn(self, txn: LoggingTransaction, room_id: str) -> List[int]:
         # First we fetch all the state groups that should be deleted, before
         # we delete that information.
         txn.execute(