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

From: John Naylor <johncnaylorls(at)gmail(dot)com>
To: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Cc: Peter Geoghegan <pg(at)bowt(dot)ie>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Andres Freund <andres(at)anarazel(dot)de>, Noah Misch <noah(at)leadboat(dot)com>
Subject: Re: Vacuum ERRORs out considering freezing dead tuples from before OldestXmin
Date: 2025-06-13 14:12:03
Message-ID: CANWCAZYe_e4Sm+AGt9UZuEcQnfW5LyAME74N+rXgNqWB1vhxMg@mail.gmail.com
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On Fri, Jun 13, 2025 at 5:23 AM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
> Yep. I have been procrastinating on swapping all this back into my
> brain. I'll start working on it today. I think I just take the
> reverted test and make the UPDATE a DELETE, set mwm 64 kB, make the
> table have 9000 rows and maybe consider using your:
>
> delete from test where ctid::text like '%,2__)';

(Swapping this part back in my brain as well...) I actually don't
think we need that where clause anymore since mwm can be super low
now, and it's a bit mysterious what it was trying to accomplish. Maybe
we can just use the lowest fill factor to reduce WAL -- having a few
dozen pages should push it over the memory limit, regardless of how
many dead tuples are on each pages.

--
John Naylor
Amazon Web Services

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