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From: Nathan Bossart <[email protected]>
To: Robert Haas <[email protected]>
Cc: David Rowley <[email protected]>
Cc: Jeremy Schneider <[email protected]>
Cc: Sami Imseih <[email protected]>
Cc: [email protected]
Subject: Re: another autovacuum scheduling thread
Date: Fri, 10 Oct 2025 14:44:22 -0500
Message-ID: <aOliFnwt6433J_Zs@nathan> (raw)
In-Reply-To: <CA+TgmoYC4ShRp8vcyrBjkefSBdFfY1fnUgCvjocN-iq55G-7bA@mail.gmail.com>
References: <[email protected]>
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	<CAApHDvpMEs3rewULyJZ=huT8ZM1C1PboV-G7K7jfGtJSgdx-fA@mail.gmail.com>
	<[email protected]>
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	<CAApHDvq76BBseUh2cG0=m=8r-j6HF_jrQt16Eszgsxp3bciGQw@mail.gmail.com>
	<aOffPCBoQLG5dGd8@nathan>
	<aOlC4aDoQcgW8ZpC@nathan>
	<CA+TgmoYC4ShRp8vcyrBjkefSBdFfY1fnUgCvjocN-iq55G-7bA@mail.gmail.com>

Thanks for taking a look.

On Fri, Oct 10, 2025 at 02:42:57PM -0400, Robert Haas wrote:
> I think this is a reasonable starting point, although I'm surprised
> that you chose to combine the sub-scores using + rather than Max.

My thinking was that we should consider as many factors as we can in the
score, not just the worst one.  If a table has medium bloat and medium
wraparound risk, should it always be lower in priority to something with
large bloat and small wraparound risk?  It seems worth exploring.  I am
curious why you first thought of Max.

> When I've thought about this problem -- and I can't claim to have
> thought about it very hard -- it's seemed to me that we need to (1)
> somehow normalize everything to somewhat similar units and (2) make
> sure that severe wraparound danger always wins over every other
> consideration, but mild wraparound danger can lose to severe bloat.

Agreed.  I need to think about this some more.  While I'm optimistic that
we could come up with some sort of normalization framework, I deperately
want to avoid super complicated formulas and GUCs, as those seem like
sure-fire ways of ensuring nothing ever gets committed.

-- 
nathan





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