Re: Temporary tables versus wraparound... again

Hi,

On 2023-04-05 10:19:10 -0400, Greg Stark wrote:
> On Wed, 5 Apr 2023 at 01:41, Greg Stark <stark(at)mit(dot)edu> wrote:
> >
> > On Wed, 29 Mar 2023 at 17:48, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> > >
> > > The patch still occasionally fails its tests under freebsd.
> > > https://cirrus-ci.com/github/postgresql-cfbot/postgresql/commitfest/42/3358
> >
> > I wonder if some other test is behaving differently on FreeBSD and
> > leaving behind a prepared transaction or a zombie session in some idle
> > state or something like that? Is there anything (aside from
> > autovacuum) connecting or running in the background in the test
> > environment that could be creating a transaction id and holding back
> > snapshot xmin?
>
> Ok, I've reproduced this here by running the tests under meson. It
> doesn't look like it's platform dependent.
>
> It seems under meson the different test suites are run in parallel or
> at least isolation/deadlock-parallel are still running stuff when the
> regression checks are running. If that's not expected then maybe
> something's not behaving as expected? I've attached pg_stat_activity
> from during the test run.

The freebsd test that failed is running tests in parallel, against an existing
cluster. In that case it's expected that there's some concurrency.

Why does this cause your tests to fail? They're in separate databases, so the
visibility effects of the concurrent tests should be somewhat limited.

Greetings,

Andres Freund