From: Tom Lane <tgl@sss.pgh.pa.us>
To: Isaac Morland <isaac.morland@gmail.com>
cc: "David G. Johnston" <david.g.johnston@gmail.com>,
        David Christensen <david@pgguru.net>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: [PATCH] GROUP BY ALL
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Comments: In-reply-to Isaac Morland <isaac.morland@gmail.com>
	message dated "Mon, 22 Jul 2024 17:40:55 -0400"
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Date: Mon, 22 Jul 2024 18:43:41 -0400
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Isaac Morland <isaac.morland@gmail.com> writes:
> And for when this might be useful, the syntax for it already exists,
> although a spurious error message is generated:

> odyssey=> select (uw_term).*, count(*) from uw_term group by uw_term;
> ERROR:  column "uw_term.term_id" must appear in the GROUP BY clause or be
> used in an aggregate function
> LINE 1: select (uw_term).*, count(*) from uw_term group by uw_term;
>                 ^

> I'm not sure exactly what's going on here

The SELECT entry is expanded into "uw_term.col1, uw_term.col2,
uw_term.col3, ...", and those single-column Vars don't match the
whole-row Var appearing in the GROUP BY list.  I guess if we
think this is important, we could add a proof rule saying that
a per-column Var is functionally dependent on a whole-row Var
of the same relation.  Odd that the point hasn't come up before
(though I guess that suggests that few people try this).

			regards, tom lane