Re: lastOverflowedXid does not handle transaction ID wraparound

( a.On Wed, Nov 3, 2021 at 11:44 AM Andrey Borodin <x4mmm(at)yandex-team(dot)ru> wrote:
> > 21 окт. 2021 г., в 09:01, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> написал(а):
> >
> > If the discussion so far is correct, the following diff will fix the
> > issue.
> >
> > diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
> > index bd3c7a47fe..19682b73ec 100644
> > --- a/src/backend/storage/ipc/procarray.c
> > +++ b/src/backend/storage/ipc/procarray.c
> > @@ -4463,6 +4463,12 @@ ExpireOldKnownAssignedTransactionIds(TransactionId xid)
> > {
> > LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
> > KnownAssignedXidsRemovePreceding(xid);
> > + /*
> > + * reset lastOverflowedXid if we know transactions that have been possiblly
> > + * running are being gone.
> > + */
> > + if (TransactionIdPrecedes(procArray->lastOverflowedXid, xid))
> > + procArray->lastOverflowedXid = InvalidTransactionId;
> > LWLockRelease(ProcArrayLock);
> > }
>
> The patch seems correct bugfix to me. The only question I have: is it right place from modularity standpoint? procArray->lastOverflowedXid is not a part of KnownAssignedTransactionIds?

It seems the right place because we take ProcArrayLock here. It would
be undesirable to take it twice. We could give a better name for
ExpireOldKnownAssignedTransactionIds() indicating that it could modify
lastOverflowedXid as well. Any ideas?

Should ExpireAllKnownAssignedTransactionIds() be also involved here?

------
Regards,
Alexander Korotkov