Re: pg_upgrade and wraparound

Andres Freund <andres(at)anarazel(dot)de> writes:
> I suspect the issue is that pg_resetwal does:
> if (set_xid != 0)
> {
> ControlFile.checkPointCopy.nextXid = set_xid;

> /*
> * For the moment, just set oldestXid to a value that will force
> * immediate autovacuum-for-wraparound. It's not clear whether adding
> * user control of this is useful, so let's just do something that's
> * reasonably safe. The magic constant here corresponds to the
> * maximum allowed value of autovacuum_freeze_max_age.
> */
> ControlFile.checkPointCopy.oldestXid = set_xid - 2000000000;
> if (ControlFile.checkPointCopy.oldestXid < FirstNormalTransactionId)
> ControlFile.checkPointCopy.oldestXid += FirstNormalTransactionId;
> ControlFile.checkPointCopy.oldestXidDB = InvalidOid;
> }

> but we have codepath that doesn't check for oldestXidDB being
> InvalidOid. Not great.

Hm, I think I'd define the problem as "pg_resetwal is violating the
expectation that oldestXidDB be valid".

However, this just explains the basically-cosmetic issue that the
complaint message mentions OID 0. It doesn't really get us to the
answer to why Alexander is seeing a failure. It might be useful
to see pg_controldata output for the old cluster, as well as
"select datname, datfrozenxid from pg_database" output from the
old cluster.

regards, tom lane