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In-Reply-To: <b579a829-987c-4a96-bbee-40b65fd18c81@gmail.com>
From: Robert Haas <robertmhaas@gmail.com>
Date: Mon, 6 Apr 2026 08:47:30 -0400
Message-ID: 
 <CA+TgmoZe2qEF45NL5GqxJ5OOygzd7LoVG+1iRCjUt7pXcd1aLQ@mail.gmail.com>
Subject: Re: pg_plan_advice
To: Andrei Lepikhov <lepihov@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Alexander Lakhin <exclusion@gmail.com>,
	Lukas Fittl <lukas@fittl.com>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Sun, Apr 5, 2026 at 3:57=E2=80=AFAM Andrei Lepikhov <lepihov@gmail.com> =
wrote:
> Looking back at the pg_plan_advice development cycle, I don=E2=80=99t see=
 many
> discussions about the design. It seems unusual given how complex the
> planner's structure is. It makes sense to follow the typical way and let
> it serve out of the contrib for some time and see if it works well.
>
> Introducing such a module into the core would effectively cancel
> alternative solutions, as seen with PGSS. Therefore, it is important to
> ensure the code is well-designed before proceeding. Do you agree?

I don't know how anyone could disagree with the idea that PostgreSQL
code should be well-designed, but that doesn't mean that I agree that
your particular design criticism is fair, and I definitely don't.

As for the amount of design discussion on the mailing list, I was
disappointed in that, too. In addition to posting to the list, I
privately asked numerous people to help review and test. Some did, but
on the whole, I was expecting a more vigorous debate and a lot of
people telling me what an idiot I am. Instead, the most common
feedback I got was some form of "can you ship it right now, please?".
That probably has less to do with the design being good (although I
believe that it is) or my code being good (although I hope that it is)
than with people just really wanting PostgreSQL to have something of
this sort. So I am somewhat afraid that this will turn out to have
more problems than anyone has noticed so far, and maybe for reasons
that will feel dumb in hindsight. But on March 12th, I asked myself
whether more people were going to be unhappy if I committed
pg_plan_advice this release cycle or if I didn't, and my educated
guess was the latter, so I committed it. If that turns out to have
been the wrong call, then I apologize to the whole community in
advance.

But I do not apologize for the fact that pg_plan_advice tries to
interpret plan trees -- which I personally think is one of the best
design decisions I have ever made while hacking on PostgreSQL -- or
that it can't interpret the variant ones that your extension produces.

--=20
Robert Haas
EDB: http://www.enterprisedb.com