Add clobbered event_id

synapse/storage/events.py

@@ -749,6 +749,7 @@ class EventsStore(SQLBaseStore):
                             "type": key[0],
                             "state_key": key[1],
                             "event_id": ev_id,
+                            "prev_event_id": to_delete.get(key, None),
                         }
                         for key, ev_id in state_deltas.iteritems()
                     ]

synapse/storage/schema/delta/42/current_state_delta.sql

@@ -19,7 +19,8 @@ CREATE TABLE current_state_delta_stream (
     room_id TEXT NOT NULL,
     type TEXT NOT NULL,
     state_key TEXT NOT NULL,
-    event_id TEXT  -- Is null if the key was removed
+    event_id TEXT,  -- Is null if the key was removed
+    prev_event_id TEXT
 );
 
 CREATE INDEX current_state_delta_stream_idx ON current_state_delta_stream(stream_id);