Avoid unnecessary database access.

synapse/handlers/relations.py

@@ -273,13 +273,28 @@ async def _get_threads_for_events(
  # Fetch thread summaries.
  summaries = await self._main_store.get_thread_summaries(event_ids)
 
- # Only fetch participated for a limited selection based on what had
+ # Only fetch whether the current user has participated in a thread based
+ # on which returned for a limited selection based on what had
  # summaries.
  thread_event_ids = [
  event_id for event_id, summary in summaries.items() if summary
  ]
- participated = await self._main_store.get_threads_participated(
- thread_event_ids, user_id
+
+ # Preseed thread participation with whether the requester send the event.
+ participated = {
+ event_id: events_by_id[event_id].sender == user_id
+ for event_id in thread_event_ids
+ }
+ # Check other events against the database.
+ participated.update(
+ await self._main_store.get_threads_participated(
+ [
+ event_id
+ for event_id in thread_event_ids
+ if not participated[event_id]
+ ],
+ user_id,
+ )
  )
 
  # Then subtract off the results for any ignored users.

tests/rest/client/test_relations.py

@@ -1073,7 +1073,7 @@ def assert_thread(bundled_aggregations: JsonDict) -> None:
  return assert_thread
 
  # A user which has sent the root event or replied has participated.
- self._test_bundled_aggregations(RelationTypes.THREAD, _gen_assert(True), 10)
+ self._test_bundled_aggregations(RelationTypes.THREAD, _gen_assert(True), 9)
  # Note that this re-uses some cached values, so the total number of
  # queries is much smaller.
  self._test_bundled_aggregations(
@@ -1131,7 +1131,7 @@ def assert_thread(bundled_aggregations: JsonDict) -> None:
  bundled_aggregations["latest_event"].get("unsigned"),
  )
 
- self._test_bundled_aggregations(RelationTypes.THREAD, assert_thread, 10)
+ self._test_bundled_aggregations(RelationTypes.THREAD, assert_thread, 9)
 
  def test_nested_thread(self) -> None:
  """