From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Wrong results from join removal with DISTINCT ON + SRF subquery
Date: Fri, 21 Aug 2026 21:15:52 -0400
Message-ID: <4122160.1787361352@sss.pgh.pa.us> (raw)
In-Reply-To: <CAMbWs4-hfd1Pyy_zBejsVUSy-3dx16rz2hgUakkKnAg3qg2q=Q@mail.gmail.com>
References: <CAMbWs4-hfd1Pyy_zBejsVUSy-3dx16rz2hgUakkKnAg3qg2q=Q@mail.gmail.com>
Richard Guo <guofenglinux@gmail.com> writes:
> Attached is a patch to not rely on DISTINCT ON for distinctness if
> there are any tlist SRFs. This is more conservative than necessary,
> since the SRFs are only postponed when there is an ORDER BY and none
> of them is in a sort/group column, but I don't think it's worth
> duplicating that logic in analyzejoins.c.
I didn't study the patch in any detail, but I concur with your
thinking here. SRFs in the tlist are kind of a legacy usage in the
first place, so I don't feel a need to expend lots of effort on
optimizing cases like this.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, guofenglinux@gmail.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Wrong results from join removal with DISTINCT ON + SRF subquery
In-Reply-To: <4122160.1787361352@sss.pgh.pa.us>
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