Re: Changing the autovacuum launcher scheduling; oldest table first algorithm

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, Ildus Kurbangaliev <i(dot)kurbangaliev(at)postgrespro(dot)ru>
Subject: Re: Changing the autovacuum launcher scheduling; oldest table first algorithm
Date: 2018-03-06 14:27:00
Message-ID: 20180306142700.wa2ba3zom22myg5q@alvherre.pgsql
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Hello

I haven't read your respective patches yet, but both these threads
brought to memory a patch I proposed a few years ago that I never
completed:

https://www.postgresql.org/message-id/flat/20130124215715.GE4528%40alvh.no-ip.org

In that thread I posted a patch to implement a prioritisation scheme for
autovacuum, based on an equation which was still under discussion when
I abandoned it. Chris Browne proposed a crazy equation to mix in both
XID age and fraction of dead tuples; probably that idea is worth
studying further. I tried to implement that in my patch but I probably
didn't do it correctly (because, as I recall, it failed to work as
expected). Nowadays I think we would also consider the multixact freeze
age, too.

Maybe that's worth giving a quick look in case some of the ideas there
are useful for the patches now being proposed.

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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