Date: Thu, 9 Oct 2025 11:13:48 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Jeremy Schneider <schneider@ardentperf.com>,
	Sami Imseih <samimseih@gmail.com>, pgsql-hackers@postgresql.org
Subject: Re: another autovacuum scheduling thread
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On Thu, Oct 09, 2025 at 04:13:23PM +1300, David Rowley wrote:
> I think the best way to understand it is if you look at
> relation_needs_vacanalyze() and see how it calculates boolean values
> for boolean output params. So, instead of calculating just a boolean
> value it instead calculates a float4 where < 1.0 means don't do the
> operation and anything >= 1.0 means do the operation. For example,
> let's say a table has 600 dead rows and the scale factor and threshold
> settings mean that autovacuum will trigger at 200 (3 times more dead
> tuples than the trigger point). That would result in the value of 3.0
> (600 / 200).  The priority for relfrozenxid portion is basically
> age(relfrozenxid) / autovacuum_freeze_max_age (plus need to account
> for mxid by doing the same for that and taking the maximum of each
> value).  For each of those component "scores", the priority for
> autovacuum would be the maximum of each of those.
> 
> Effectively, it's a method of aligning the different units of measure,
> transactions or tuples into a single value which is calculated based
> on the very same values that we use today to trigger autovacuums.

I like the idea of a "score" approach, but I'm worried that we'll never
come to an agreement on the formula to use.  Perhaps we'd have more luck
getting consensus on a multifaceted strategy if we kept it brutally simple.
IMHO it's worth a try...

-- 
nathan