Richard van der Hoff

For reference, here is a query which will confirm if your system has been affected by this bug: ```sql select * from event_forward_extremities efe left join events e using (event_id)...

> I lost all attachments sometime last year. attachments as in uploaded media? shouldn't be a factor. > I've dumped and restored the postgresql database a few weeks back due...

To work around the problem, it should be safe to remove the bad rows from `event_forward_extremities` with: ```sql DELETE FROM event_forward_extremities WHERE event_id='$....'; ``` ... and then restart synapse. (Note:...

@travisghansen: > EDIT: after some time the issue cleared itself up (after deleting the db entries). Likely Synapse had cached the deleted rows. I've updated the instructions to suggest restarting...

People encountering this issue **as confirmed by the query at https://github.com/matrix-org/synapse/issues/12507#issuecomment-1104903000**: First: note that this error is reporting corruption in your database which may have happened **a long time ago**....

@MparkG: as the earlier comments make very clear: "If it doesn't [return any rows] you likely have a different problem and should open a separate issue".

@travisghansen thanks for the answers, though honestly they don't help me get any closer to understanding what can have caused this. Be wary of retention: it's not a well-used feature...

I've seen history purges cause a big explosion in state groups in the past: https://github.com/matrix-org/synapse/issues/3364#issuecomment-395263702.

sigh. That's annoying, as it makes #9677 harder.

I've created a separate issue (#10545) to handle removing `trust_identity_server_for_password_reset`, since that's rather easier.