Also batch persist

synapse/handlers/federation_event.py

@@ -1367,9 +1367,9 @@ async def _get_state_ids_after_missing_prev_event(
             )
 
         if remote_event.is_state() and remote_event.rejected_reason is None:
-            state_map[
-                (remote_event.type, remote_event.state_key)
-            ] = remote_event.event_id
+            state_map[(remote_event.type, remote_event.state_key)] = (
+                remote_event.event_id
+            )
 
         return state_map
 
@@ -1766,14 +1766,16 @@ async def prep(event: EventBase) -> None:
             if (i + 1) % 1000 == 0:
                 await self._clock.sleep(0)
 
-        await self.persist_events_and_notify(
-            room_id,
-            events_and_contexts_to_persist,
-            # Mark these events backfilled as they're historic events that will
-            # eventually be backfilled. For example, missing events we fetch
-            # during backfill should be marked as backfilled as well.
-            backfilled=True,
-        )
+        # Also persist the new event in batches for similar reasons as above.
+        for batch in batch_iter(events_and_contexts_to_persist, 1000):
+            await self.persist_events_and_notify(
+                room_id,
+                batch,
+                # Mark these events backfilled as they're historic events that will
+                # eventually be backfilled. For example, missing events we fetch
+                # during backfill should be marked as backfilled as well.
+                backfilled=True,
+            )
 
     @trace
     async def _check_event_auth(