Use simple_upsert_txn for sliding_sync_membership_snapshots in background update

synapse/storage/databases/main/events_bg_updates.py

@@ -1982,42 +1982,41 @@ class EventsBackgroundUpdatesStore(StreamWorkerStore, StateDeltasStore, SQLBaseS
                     membership_info.membership_event_stream_ordering
                 )
 
-                # Pulling keys/values separately is safe and will produce congruent
-                # lists
-                insert_keys = insert_map.keys()
-                insert_values = insert_map.values()
-                # We don't need to update the state `ON CONFLICT` because we never
-                # partially insert/update the snapshots and anything already there is
-                # up-to-date EXCEPT for the `forgotten` field since that is updated out
-                # of band from the membership changes.
+                # We don't need to upsert the state because we never partially
+                # insert/update the snapshots and anything already there is up-to-date
+                # EXCEPT for the `forgotten` field since that is updated out-of-band
+                # from the membership changes.
                 #
+                # Even though we're only doing insertions, we're using
+                # `simple_upsert_txn()` here to avoid unique violation errors that would
+                # happen from `simple_insert_txn()`
+                self.db_pool.simple_upsert_txn(
+                    txn,
+                    table="sliding_sync_membership_snapshots",
+                    keyvalues={"room_id": room_id, "user_id": user_id},
+                    values={},
+                    insertion_values={
+                        **insert_map,
+                        "sender": sender,
+                        "membership_event_id": membership_event_id,
+                        "membership": membership,
+                        "event_stream_ordering": membership_event_stream_ordering,
+                    },
+                )
                 # We need to find the `forgotten` value during the transaction because
                 # we can't risk inserting stale data.
                 txn.execute(
-                    f"""
-                    INSERT INTO sliding_sync_membership_snapshots
-                        (room_id, user_id, sender, membership_event_id, membership, forgotten, event_stream_ordering
-                        {("," + ", ".join(insert_keys)) if insert_keys else ""})
-                    VALUES (
-                        ?, ?, ?, ?, ?,
-                        (SELECT forgotten FROM room_memberships WHERE event_id = ?),
-                        ?
-                        {("," + ", ".join("?" for _ in insert_values)) if insert_values else ""}
-                    )
-                    ON CONFLICT (room_id, user_id)
-                    DO UPDATE SET
-                        forgotten = EXCLUDED.forgotten
+                    """
+                    UPDATE sliding_sync_membership_snapshots
+                    SET
+                        forgotten = (SELECT forgotten FROM room_memberships WHERE event_id = ?)
+                    WHERE room_id = ? and user_id = ?
                     """,
-                    [
+                    (
+                        membership_event_id,
                         room_id,
                         user_id,
-                        sender,
-                        membership_event_id,
-                        membership,
-                        membership_event_id,
-                        membership_event_stream_ordering,
-                    ]
-                    + list(insert_values),
+                    ),
                 )
 
         await self.db_pool.runInteraction(