Improve redact_on_ban performance (#18851)

Co-authored-by: Erik Johnston <[email protected]>

Author: H-Shay

changelog.d/18851.bugfix

@@ -0,0 +1 @@
+Improve database performance of [MSC4293](https://github.com/matrix-org/matrix-spec-proposals/pull/4293) - Redact on Kick/Ban.

synapse/storage/databases/main/events_worker.py

@@ -81,6 +81,7 @@
     DatabasePool,
     LoggingDatabaseConnection,
     LoggingTransaction,
+    make_tuple_in_list_sql_clause,
 )
 from synapse.storage.types import Cursor
 from synapse.storage.util.id_generators import (
@@ -1617,21 +1618,28 @@ def _fetch_event_rows(
             # likely that some of these events may be for the same room/user combo, in
             # which case we don't need to do redundant queries
             to_check_set = set(to_check)
-            for room_and_user in to_check_set:
-                room_redactions_sql = "SELECT redacting_event_id, redact_end_ordering FROM room_ban_redactions WHERE room_id = ? and user_id = ?"
-                txn.execute(room_redactions_sql, room_and_user)
-
-                res = txn.fetchone()
-                # we have a redaction for a room, user_id combo - apply it to matching events
-                if not res:
-                    continue
+            room_redaction_sql = "SELECT room_id, user_id, redacting_event_id, redact_end_ordering FROM room_ban_redactions WHERE "
+            (
+                in_list_clause,
+                room_redaction_args,
+            ) = make_tuple_in_list_sql_clause(
+                self.database_engine, ("room_id", "user_id"), to_check_set
+            )
+            txn.execute(room_redaction_sql + in_list_clause, room_redaction_args)
+            for (
+                returned_room_id,
+                returned_user_id,
+                redacting_event_id,
+                redact_end_ordering,
+            ) in txn:
                 for e_row in events:
                     e_json = json.loads(e_row.json)
                     room_id = e_json.get("room_id")
                     user_id = e_json.get("sender")
+                    room_and_user = (returned_room_id, returned_user_id)
+                    # check if we have a redaction match for this room, user combination
                     if room_and_user != (room_id, user_id):
                         continue
-                    redacting_event_id, redact_end_ordering = res
                     if redact_end_ordering:
                         # Avoid redacting any events arriving *after* the membership event which
                         # ends an active redaction - note that this will always redact