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From: Jacob Champion <jacob.champion@enterprisedb.com>
Date: Mon, 23 Feb 2026 17:05:45 -0800
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 <CAOYmi+kC3AN0QJKT0OunHCmi4UU7-15eu7w-DY5ckOgHiQE1QA@mail.gmail.com>
Subject: Re: pgsql: libpq: Grease the protocol by default
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Jelte Fennema-Nio <postgres@jeltef.nl>,
 pgsql-hackers@lists.postgresql.org,
	Andrew Dunstan <andrew@dunslane.net>
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On Mon, Feb 23, 2026 at 4:45=E2=80=AFPM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Jacob Champion <jacob.champion@enterprisedb.com> writes:
> > Something like the attached (tested only against 9.2 so far)? I would
> > plan to backpatch after feature freeze is lifted.

(er, should have been "release freeze", though we're clearly in no hurry)

> Also: I was initially baffled why you thought this needs
> back-patching, but I guess you have one eye on packagers like
> Debian who think they can make older versions use newer libpq.so.

Right.

> It'd be good to spell out that reasoning in the commit message.

Okay, will do.

> It's not obvious to me where the problem lies.  I can replicate
> the failure by trying to use HEAD's psql to connect to a 9.2
> server, but adding -d "max_protocol_version=3D3.0" makes psql happy,
> so why not pg_dumpall?

Hmmm, looks like the -dump1.log output is actually from *before*
pg_upgrade actually runs:

    https://github.com/PGBuildFarm/client-code/blob/28d7e945cc2a27fecdf4cc6=
85782821ca504db5d/PGBuild/Modules/TestUpgradeXversion.pm#L514

So that will still need to be modified in the buildfarm client,
independently of my patch. (I reproduced the error with a bare
pg_upgrade invocation and didn't think to look closer; sorry for the
confusion.)

--Jacob