Re: Teaching planner to short-circuit empty UNION/EXCEPT/INTERSECT inputs

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: David Rowley <dgrowleyml(at)gmail(dot)com>
Cc: PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Teaching planner to short-circuit empty UNION/EXCEPT/INTERSECT inputs
Date: 2025-10-02 15:18:56
Message-ID: 1064547.1759418336@sss.pgh.pa.us
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David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> Good idea. Less code and still get to keep the one that did well in
> the benchmark. See attached.

0001's change in is_dummy_rel() seems like a complete hack, especially
since you didn't bother to change the adjacent comment. Why is that
necessary?

v2 LGTM otherwise.

regards, tom lane

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