On Wed, Nov 23, 2022 at 2:54 AM Alvaro Herrera <alvhe...@alvh.no-ip.org> wrote: > Something like the attached. It would result in output like this: > WARNING: new multixact has more than one updating member: 0 2[17378 (keysh), > 17381 (nokeyupd)] > > Then it should be possible to trace (in pg_waldump output) the > operations of each of the transactions that have any status in the > multixact that includes some form of "upd".
That seems very useful. Separately, I wonder if it would make sense to add additional defensive checks to FreezeMultiXactId() for this. There is an assertion that should catch the presence of multiple updaters in a single Multi when it looks like we have to generate a new Multi to carry the XID members forward (typically something we only need to do during a VACUUM FREEZE). We could at least make that "Assert(!TransactionIdIsValid(update_xid));" line into a defensive "can't happen" ereport(). It couldn't hurt, at least -- we already have a similar relfrozenxid check nearby, added after the "freeze the dead" bug was fixed. -- Peter Geoghegan
