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From: John Naylor <johncnaylorls@gmail.com>
Date: Thu, 11 Dec 2025 09:53:09 +0700
Message-ID: 
 <CANWCAZY529EPHyo1kLnEzjFBq-UaDPc3KErK=ApqDZZ1Oc-XHg@mail.gmail.com>
Subject: Re: Add a greedy join search algorithm to handle large join problems
To: Tomas Vondra <tomas@vondra.me>
Cc: Chengpeng Yan <chengpeng_yan@outlook.com>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
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On Wed, Dec 10, 2025 at 5:20=E2=80=AFPM Tomas Vondra <tomas@vondra.me> wrot=
e:
> I did however notice an interesting thing - running EXPLAIN on the 99
> queries (for 3 scales and 0/4 workers, so 6x 99) took this much time:
>
> master:       8s
> master/geqo: 20s
> master/goo:   5s

> It's nice that "goo" seems to be faster than "geqo" - assuming the plans
> are comparable or better. But it surprised me switching to geqo makes it
> slower than master. That goes against my intuition that geqo is meant to
> be cheaper/faster join order planning. But maybe I'm missing something.

Yeah, that was surprising. It seems that geqo has a large overhead, so
it takes a larger join problem for the asymptotic behavior to win over
exhaustive search.

--
John Naylor
Amazon Web Services