state resets still happen in v2 rooms

This issue has been migrated from #8629.

I just upgraded #synapse:matrix.org because I got fed up of losing my ops bit. It was a v4 room.

EDIT 2022-08-03 by @DMRobertson: if you suspect you have seen a state reset, please provide:

the room_id of the room with the reset
the type and state_key that suffered a reset
the event_id of the piece of state after the reset
ideally, the event_id of the piece of state before the reset
- failing that, a rough time range before and after the reset occurred (including timezone information)

To confirm if this really is a server-side state reset (rather than e.g. matrix-org/matrix-spec#1209), server administrators can run the following queries.

SELECT *
FROM current_state_delta_stream 
WHERE
    room_id ='<room id>'
    and type='<type of event>'' 
    and state_key='<state key>'
ORDER BY stream_id asc;

SELECT *
FROM current_state_events
WHERE
    room_id ='<room id>'
    and type='<type of event>'' 
    and state_key='<state key>';

The last row in the event_id columns from these two queries should match. It represents the event which currently describes the relevant piece of state from your server's point of view.

element-hq / synapse

state resets still happen in v2 rooms #8629