From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: Adrian Klaver <adrian.klaver@aklaver.com>,
        PALAYRET Jacques <jacques.palayret@meteo.fr>,
        pgsql-general@lists.postgresql.org
Subject: Re: PostgreSQL query with FULL OUTER JOIN and subquery using column of GROUP BY expression ERROR: subquery uses ungrouped column from outer query
In-reply-to: <295608.1772040819@sss.pgh.pa.us>
References: <970600119.344834366.1772018068349.JavaMail.zimbra@meteo.fr> <52acd108-2949-4762-80c2-c761662fde73@aklaver.com> <CAKFQuwY27TZSERWdmC+=RO+B86KAOSW+CeJSSL52eUZQLYZsrA@mail.gmail.com> <295608.1772040819@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Wed, 25 Feb 2026 12:33:39 -0500"
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Date: Wed, 25 Feb 2026 17:44:43 -0500
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I wrote:
> "David G. Johnston" <david.g.johnston@gmail.com> writes:
>> My first impression is that this is a bug.  Especially since the query
>> apparently executes in both left-join and right-join modes.

> Well, it's a longstanding deficiency anyway.
> ...
> Still, it is annoying.  I wonder if there's a way to do it without
> either a large amount of new code or exponential time spent
> trying useless subexpression matches...

I've posted a draft fix for that at

https://www.postgresql.org/message-id/flat/531183.1772058731%40sss.pgh.pa.us

			regards, tom lane