Re: [PoC] Reducing planning time when tables have many partitions

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From: Alvaro Herrera <[email protected]>
To: Yuya Watari <[email protected]>
Cc: Ashutosh Bapat <[email protected]>
Cc: Dmitry Dolgov <[email protected]>
Cc: PostgreSQL Developers <[email protected]>
Cc: jian he <[email protected]>
Cc: Alena Rybakina <[email protected]>
Cc: Andrei Lepikhov <[email protected]>
Cc: David Rowley <[email protected]>
Cc: Thom Brown <[email protected]>
Cc: Zhang Mingli <[email protected]>
Cc: Tom Lane <[email protected]>
Subject: Re: [PoC] Reducing planning time when tables have many partitions
Date: Thu, 12 Dec 2024 13:09:26 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAJ2pMkY-Vd55REn3N1ACuRS0UT5QEe38r2pJ6=MatLKZkXHOxg@mail.gmail.com>

Hello Yuya,

On 2024-Dec-11, Yuya Watari wrote:

> On Tue, Dec 3, 2024 at 7:38 PM Alvaro Herrera <[email protected]> wrote:
> >
> > I don't think planning time in assert-enabled builds is something we
> > should worry about, at all.  Planning time in production builds is the
> > important one.
> 
> Thank you for your reply. Making debug builds too slow is not good for
> developers,

I'm repeating myself, but I disagree that this is something we should
spend _any_ time on.  Developers running assertion-enabled builds do not
care if a complicated query with one thousand partitions is planned in
500 ms instead of 300 ms.  Heck, I bet nobody cares if it took 2000 ms
either, because, you know what?  The developers don't have a thousand
partitions to begin with; if they do, it's precisely because they want
to measure this kind of effect.  This is not going to bother anyone
ever, unless you stick a hundred of these queries in the regression
tests.  In regression tests you're going to have, say, 64 partitions at
most, because having more than that doesn't test anything additional;
having that go from 40 ms to 60 ms (or whatever) isn't going to bother
anyone.

If anything, you can add a note to remove the USE_ASSERTIONS blocks once
we get past the beta process; by then any bugs will have been noticed
and the asserts will be of less value.

I would like to see this patch series get committed, and this concern
about planning time in development builds under conditions that are
unrealistic for testing is slowing the process down.  (The process is
slow enough.  This patch has already missed two releases.)  Please stop.

Memory usage and planning time in production builds is important.  You
can better spend your energy there.

Thanks

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"La gente vulgar sólo piensa en pasar el tiempo;
el que tiene talento, en aprovecharlo"

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