Fix downgrading to previous version of Synapse (#15907)

We do this by marking the constraint as deferrable.

1 files changed, 3 insertions, 1 deletions

diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py

index dabe603c8c..b2cda52ce5 100644
--- a/synapse/storage/databases/main/event_federation.py
+++ b/synapse/storage/databases/main/event_federation.py
@@ -146,7 +146,9 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
                 update_name="event_forward_extremities_event_id_foreign_key_constraint_update",
                 table="event_forward_extremities",
                 constraint_name="event_forward_extremities_event_id",
-                constraint=ForeignKeyConstraint("events", [("event_id", "event_id")]),
+                constraint=ForeignKeyConstraint(
+                    "events", [("event_id", "event_id")], deferred=True
+                ),
                 unique_columns=("event_id", "room_id"),
             )