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From: Dominique Devienne <ddevienne@gmail.com>
Date: Wed, 11 Jun 2025 11:26:18 +0200
Message-ID: <CAFCRh-8twaDLV2uEy=R8e7U29LOAPhRN8vVzq712UE_J=7Ld4w@mail.gmail.com>
Subject: Re: is pg_stat_activity "transactional"? How fast does it update?
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-general@lists.postgresql.org
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On Tue, Jun 10, 2025 at 5:46=E2=80=AFPM Dominique Devienne <ddevienne@gmail=
.com> wrote:
> On Tue, Jun 10, 2025 at 4:27=E2=80=AFPM Tom Lane <tgl@sss.pgh.pa.us> wrot=
e:
> > PQfinish is asynchronous: [...]
> > [...] pg_stat_activity() takes a snapshot of the view's contents
> Many thanks Tom. Didn't know either of those facts.

Hi. I ended up polling pg_stat_activity to wait for the disappearance
of the backend, to avoid the race in my unit tests. Initially
pg_stat_clear_snapshot() seemed to help, but then it didn't. Not
ideal, but I don't see any solution (work-around, really). There's a
new LOGIN event trigger, but no symmetrical FINISH one, and those are
restricted to privileged users, so useless in my case. Oh well. --DD