From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: pgsql-hackers@postgresql.org, David Rowley <dgrowleyml@gmail.com>
Subject: Re: Unfortunate pushing down of expressions below sort
In-reply-to: <1668738.1770336789@sss.pgh.pa.us>
References: <qddu2agmbiadpqkavqlamccrqxg6rm64sdq6q7ihpyndyfim6k@2dpox3fupa2g> <1668738.1770336789@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Thu, 05 Feb 2026 19:13:09 -0500"
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Date: Thu, 05 Feb 2026 20:02:31 -0500
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Precedence: bulk

I wrote:
> Yeah.  That's a hangover from an ancient decision that sort/limit
> would always be applied at the top of the plan tree.  I'm too
> lazy to check the details right now, but I think we already relaxed
> that in some cases (or maybe it was about evaluating stuff
> before/after GROUP BY?).

Ah, right: see make_sort_input_target() and its very extensive
comment in planner.c.  I wonder why that didn't trigger in
your example.

			regards, tom lane