Return an immutable value from get_latest_event_ids_in_room. (#16326)

1 files changed, 4 insertions, 5 deletions

diff --git a/synapse/storage/controllers/persist_events.py b/synapse/storage/controllers/persist_events.py
index 6864f93090..f39ae2d635 100644
--- a/synapse/storage/controllers/persist_events.py
+++ b/synapse/storage/controllers/persist_events.py
@@ -19,6 +19,7 @@ import logging
 from collections import deque
 from typing import (
     TYPE_CHECKING,
+    AbstractSet,
     Any,
     Awaitable,
     Callable,
@@ -618,7 +619,7 @@ class EventsPersistenceStorageController:
                         )
 
                     for room_id, ev_ctx_rm in events_by_room.items():
-                        latest_event_ids = set(
+                        latest_event_ids = (
                             await self.main_store.get_latest_event_ids_in_room(room_id)
                         )
                         new_latest_event_ids = await self._calculate_new_extremities(
@@ -740,7 +741,7 @@ class EventsPersistenceStorageController:
         self,
         room_id: str,
         event_contexts: List[Tuple[EventBase, EventContext]],
-        latest_event_ids: Collection[str],
+        latest_event_ids: AbstractSet[str],
     ) -> Set[str]:
         """Calculates the new forward extremities for a room given events to
         persist.
@@ -758,8 +759,6 @@ class EventsPersistenceStorageController:
             and not event.internal_metadata.is_soft_failed()
         ]
 
-        latest_event_ids = set(latest_event_ids)
-
         # start with the existing forward extremities
         result = set(latest_event_ids)
 
@@ -798,7 +797,7 @@ class EventsPersistenceStorageController:
         self,
         room_id: str,
         events_context: List[Tuple[EventBase, EventContext]],
-        old_latest_event_ids: Set[str],
+        old_latest_event_ids: AbstractSet[str],
         new_latest_event_ids: Set[str],
     ) -> Tuple[Optional[StateMap[str]], Optional[StateMap[str]], Set[str]]:
         """Calculate the current state dict after adding some new events to