Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin

From: Andres Freund <andres(at)anarazel(dot)de>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Melanie Plageman <melanieplageman(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Noah Misch <noah(at)leadboat(dot)com>
Subject: Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin
Date: 2024-06-25 20:41:36
Message-ID: 20240625204136.3s3j5peibht7eekb@alap3.anarazel.de
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On 2024-06-25 14:35:00 -0400, Robert Haas wrote:
> Is there any way that we could instead tweak things so that we adjust
> the visibility test object itself? Like can have a GlobalVisTest API
> where we can supply the OldestXmin from the VacuumCutoffs and have it
> ... do something useful with that?

I doubt that's doable in the back branches. And even on HEAD, I don't think
it's a particularly attractive option - there's just a global vistest for each
of the types of objects with a specific horizon (they need to be updated
occasionally, e.g. when taking snapshots). So there's not really a spot to put
an associated OldestXmin. We could put it there and remove it at the end of
vacuum / in an exception handler, but that seems substantially worse.

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