Fix 'rejected_events_metadata' background update (#9537)

Turns out matrix.org has an event that has duplicate auth events (which really isn't supposed to happen, but here we are). This caused the background update to fail due to `UniqueViolation`.
matrix-org · Mar 3, 2021 · a4fa044 · a4fa044
1 parent 922788c
commit a4fa044
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diff --git a/changelog.d/9537.bugfix b/changelog.d/9537.bugfix
@@ -0,0 +1 @@
+Fix rare edge case that caused a background update to fail if the server had rejected an event that had duplicate auth events.
diff --git a/synapse/storage/databases/main/events_bg_updates.py b/synapse/storage/databases/main/events_bg_updates.py
@@ -696,7 +696,9 @@ def get_rejected_events(
                 )
 
             if not has_event_auth:
-                for auth_id in event.auth_event_ids():
+                # Old, dodgy, events may have duplicate auth events, which we
+                # need to deduplicate as we have a unique constraint.
+                for auth_id in set(event.auth_event_ids()):
                     auth_events.append(
                         {
                             "room_id": event.room_id,
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fix rare edge case that caused a background update to fail if the server had rejected an event that had duplicate auth events.