diff --git a/changelog.d/6954.misc b/changelog.d/6954.misc
new file mode 100644
index 0000000000..8b84ce2f19
--- /dev/null
+++ b/changelog.d/6954.misc
@@ -0,0 +1 @@
+Minor perf fixes to `get_auth_chain_ids`.
diff --git a/synapse/storage/data_stores/main/event_federation.py b/synapse/storage/data_stores/main/event_federation.py
index e16da2577d..750ec1b70d 100644
--- a/synapse/storage/data_stores/main/event_federation.py
+++ b/synapse/storage/data_stores/main/event_federation.py
@@ -16,7 +16,6 @@ import itertools
import logging
from typing import List, Optional, Set
-from six.moves import range
from six.moves.queue import Empty, PriorityQueue
from twisted.internet import defer
@@ -28,6 +27,7 @@ from synapse.storage.data_stores.main.events_worker import EventsWorkerStore
from synapse.storage.data_stores.main.signatures import SignatureWorkerStore
from synapse.storage.database import Database
from synapse.util.caches.descriptors import cached
+from synapse.util.iterutils import batch_iter
logger = logging.getLogger(__name__)
@@ -88,14 +88,12 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
front = set(event_ids)
while front:
new_front = set()
- front_list = list(front)
- chunks = [front_list[x : x + 100] for x in range(0, len(front), 100)]
- for chunk in chunks:
+ for chunk in batch_iter(front, 100):
clause, args = make_in_list_sql_clause(
txn.database_engine, "event_id", chunk
)
- txn.execute(base_sql + clause, list(args))
- new_front.update([r[0] for r in txn])
+ txn.execute(base_sql + clause, args)
+ new_front.update(r[0] for r in txn)
new_front -= ignore_events
new_front -= results
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index 3eeb2f7c04..6dcb5c04da 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -1504,7 +1504,7 @@ class Database(object):
def make_in_list_sql_clause(
database_engine, column: str, iterable: Iterable
-) -> Tuple[str, Iterable]:
+) -> Tuple[str, list]:
"""Returns an SQL clause that checks the given column is in the iterable.
On SQLite this expands to `column IN (?, ?, ...)`, whereas on Postgres
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