Faster load recents for sync (#16783)

This hopefully reduces the amount of state we need to keep in memory

1 files changed, 16 insertions, 1 deletions

diff --git a/synapse/storage/databases/main/state.py b/synapse/storage/databases/main/state.py
index 06c44bb563..8006046453 100644
--- a/synapse/storage/databases/main/state.py
+++ b/synapse/storage/databases/main/state.py
@@ -24,6 +24,7 @@ from typing import (
     Any,
     Collection,
     Dict,
+    FrozenSet,
     Iterable,
     List,
     Mapping,
@@ -55,7 +56,7 @@ from synapse.storage.database import (
 )
 from synapse.storage.databases.main.events_worker import EventsWorkerStore
 from synapse.storage.databases.main.roommember import RoomMemberWorkerStore
-from synapse.types import JsonDict, JsonMapping, StateKey, StateMap
+from synapse.types import JsonDict, JsonMapping, StateKey, StateMap, StrCollection
 from synapse.types.state import StateFilter
 from synapse.util.caches import intern_string
 from synapse.util.caches.descriptors import cached, cachedList
@@ -323,6 +324,20 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
             "get_partial_current_state_ids", _get_current_state_ids_txn
         )
 
+    async def check_if_events_in_current_state(
+        self, event_ids: StrCollection
+    ) -> FrozenSet[str]:
+        """Checks and returns which of the given events is part of the current state."""
+        rows = await self.db_pool.simple_select_many_batch(
+            table="current_state_events",
+            column="event_id",
+            iterable=event_ids,
+            retcols=("event_id",),
+            desc="check_if_events_in_current_state",
+        )
+
+        return frozenset(event_id for event_id, in rows)
+
     # FIXME: how should this be cached?
     @cancellable
     async def get_partial_filtered_current_state_ids(