Re: Turning off HOT/Cleanup sometimes

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Greg Stark <stark(at)mit(dot)edu>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Simon Riggs <simon(dot)riggs(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Robert Haas <robertmhaas(at)gmail(dot)com>
Subject: Re: Turning off HOT/Cleanup sometimes
Date: 2015-04-22 21:17:36
Message-ID: 20150422211736.GF13362@momjian.us
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On Wed, Apr 22, 2015 at 06:07:00PM -0300, Alvaro Herrera wrote:
> > Good point, but doesn't vacuum remove the need for pruning as it removes
> > all the old rows?
>
> Sure. The point, I think, is to make autovacuum runs of some sort that
> don't actually vacuum but only do HOT-pruning. Maybe this is a
> reasonable solution to the problem that queries don't prune anymore
> after Simon's patch. If we made autovac HOT-prune periodically, we
> could have read-only queries prune only already-dirty pages. Of course,
> that would need further adjustments to default number of autovac
> workers, I/O allocation, etc.

Do we really want to make vacuum more complex for this? vacuum does
have the delay settings we would need though.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +

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