From: Antonin Houska <ah@cybertec.at>
To: Michael Paquier <michael@paquier.xyz>
cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
    pgsql-hackers@lists.postgresql.org
Subject: Re: Teach isolation tester about injection points in background
 workers
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Comments: In-reply-to Michael Paquier <michael@paquier.xyz>
   message dated "Wed, 25 Mar 2026 11:19:15 +0900."
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Date: Mon, 30 Mar 2026 15:29:47 +0200
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Michael Paquier <michael@paquier.xyz> wrote:

> On Tue, Mar 24, 2026 at 04:25:47PM +0530, Srinath Reddy Sadipiralla wrot=
e:
> > +1. I was thinking can we move the logic of checking if bg workers are=
 the
> > reason of blocking the main backend
> > inside pg_isolation_test_session_is_blocked
> > to make it cleaner, and regarding "XXX Should we use a separate query =
for
> > that?"
> > i am confused here IIUC if we keep it as 1 query using UNION every tim=
e its
> > for sure
> > that both the queries will run, which can increase more execution time=
 but
> > less libpq/socket
> > calls, but if we send as 2 queries if 1st query doesn't returns true w=
e
> > have to go and
> > check the other query, so here if 2 queries ran then execution +
> > libpq/socket calls overhead,
> > so i am slightly inclined towards separating the queries , so that if =
1st
> > gets satisfied then
> > we don't touch the 2nd query at all, please correct me if i am wrong h=
ere :)
> =

> Is there a benefit in this change outside the hypothetical REPACK
> CONCURRENTLY?

Not at the moment. Perhaps I shouldn't pursue this patch until there's an
injection point in the tree that needs that.

> Using separating queries may make more sense on readability ground, at
> least.

Agreed.

-- =

Antonin Houska
Web: https://www.cybertec-postgresql.com