On Sun, May 16, 2021 at 04:23:02PM -0400, Tom Lane wrote:
> And the reason oldestXID contains that is that pg_upgrade applied
> pg_resetwal, which does this:
>
> /*
> * 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;
>
> So it seems like we should do some combination of these things:
>
> 1. Fix FullXidRelativeTo to be a little less trusting. It'd
> probably be sane to make it return FirstNormalTransactionId
> when it'd otherwise produce a wrapped-around FullXid, but is
> there any situation where we'd want it to throw an error instead?
>
> 2. Change pg_resetwal to not do the above. It's not entirely
> apparent to me what business it has trying to force
> autovacuum-for-wraparound anyway, but if it does need to do that,
> can we devise a less klugy method?
Sorry, I wish I could help with this pg_upgrade problem, but I have no
idea why pg_resetwal is doing that. Pg_upgrade is supposed to be
turning off autovacuum, though I think we have had some cases where it
could not be fully turned off and consumption of many xids caused
autovacuum to run and break pg_upgrade.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com
If only the physical world exists, free will is an illusion.
