Re: recovering from "found xmin ... from before relfrozenxid ..."

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>, Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>, "Andrey M(dot) Borodin" <x4mmm(at)yandex-team(dot)ru>, MBeena Emerson <mbeena(dot)emerson(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>
Subject: Re: recovering from "found xmin ... from before relfrozenxid ..."
Date: 2020-09-21 21:20:03
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On 2020-09-21 17:03:53 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2020-09-21 16:40:40 -0400, Tom Lane wrote:
> >> Andres Freund <andres(at)anarazel(dot)de> writes:
> >>> I think that's an argument for what I suggested elsewhere, which is that
> >>> we should move the logic for a different horizon for temp tables out of
> >>> vacuum_set_xid_limits, and into procarray.
> >> But procarray does not seem like a great place for
> >> table-persistence-dependent decisions either?
> > That ship has sailed a long long time ago though. GetOldestXmin() has
> > looked at the passed in relation for a quite a while, and even before
> > that we had logic about 'allDbs' etc. It doesn't easily seem possible
> > to avoid that, given how intimately that's coupled with how snapshots
> > are built and used, database & vacuumFlags checks etc.
> OK. Given that you've got strong feelings about this, do you want to
> propose a patch? I'm happy to fix it, since it's at least in part my
> bug, but I probably won't do it exactly like you would.

I can give it a try. I can see several paths of varying invasiveness,
not sure yet what the best approach is. Let me think about if for a bit.


Andres Freund

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