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From: Peter Geoghegan <pg@bowt.ie>
Date: Tue, 15 Feb 2022 15:17:25 -0800
Message-ID: <CAH2-WznMo_aEQJJrD1G70RbbWRB9C3gFf3Am6emYrWSTh6wu=w@mail.gmail.com>
Subject: Re: do only critical work during single-user vacuum?
To: John Naylor <john.naylor@enterprisedb.com>
Cc: Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Tue, Feb 15, 2022 at 9:28 AM Peter Geoghegan <pg@bowt.ie> wrote:
> On Mon, Feb 14, 2022 at 10:04 PM John Naylor
> <john.naylor@enterprisedb.com> wrote:
> > Well, the point of inventing this new vacuum mode was because I
> > thought that upon reaching xidStopLimit, we couldn't issue commands,
> > period, under the postmaster. If it was easier to get a test instance
> > to xidStopLimit, I certainly would have discovered this sooner.
>
> I did notice from my own testing of the failsafe (by artificially
> inducing wraparound failure using an XID burning C function) that
> autovacuum seemed to totally correct the problem, even when the system
> had already crossed xidStopLimit - it came back on its own. I wasn't
> completely sure of how robust this effect was, though.

It seemed worth noting this in comments above
should_attempt_truncation(). Pushed a commit to do that just now.

Thanks
-- 
Peter Geoghegan