Date: Fri, 29 Aug 2014 09:45:28 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
Cc: Robert Haas <robertmhaas@gmail.com>,
 Amit Kapila <amit.kapila16@gmail.com>,
 Haribabu Kommi <kommi.haribabu@gmail.com>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: Per table autovacuum vacuum cost limit behaviour
 strange
Message-ID: <20140829134528.GE7705@eldon.alvh.no-ip.org>
References: 
 <CAA4eK1LwFs9iM-rUdfOrZE5MvjSxMM9ZbPbzv1SeWgGYu-O=VQ@mail.gmail.com>
 <53672F63.3080400@catalyst.net.nz>
 <CAA4eK1KDAUP=g59ku_0ekDoRjaGfEamyadQn5rJVt3j5oErLXg@mail.gmail.com>
 <53686F22.8030300@catalyst.net.nz>
 <20140826161911.GE6343@eldon.alvh.no-ip.org>
 <CA+Tgmoav37msTP0pVsrEYz4LBYU6SETMZGYTgPo5AEOC0yCMbA@mail.gmail.com>
 <20140828173646.GR7046@eldon.alvh.no-ip.org>
 <CA+TgmobKRho2y4tLSMQCqcRcdhVE7GMoATa=5JKo9wgV47Tc2Q@mail.gmail.com>
 <20140828205635.GA7705@eldon.alvh.no-ip.org>
 <54000317.6030604@catalyst.net.nz>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <54000317.6030604@catalyst.net.nz>
User-Agent: Mutt/1.5.21 (2010-09-15)
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Mark Kirkwood wrote:
> On 29/08/14 08:56, Alvaro Herrera wrote:
> >Robert Haas wrote:
> >
> >>I agree that you might not like that.  But you might not like having
> >>the table vacuumed slower than the configured rate, either.  My
> >>impression is that the time between vacuums isn't really all that
> >>negotiable for some people.  I had one customer who had horrible bloat
> >>issues on a table that was vacuumed every minute; when we changed the
> >>configuration so that it was vacuumed every 15 seconds, those problems
> >>went away.
> >
> >Wow, that's extreme.  For that case you can set
> >autovacuum_vacuum_cost_limit to 0, which disables the whole thing and
> >lets vacuum run at full speed -- no throttling at all.  Would that
> >satisfy the concern?
> 
> Well no - you might have a whole lot of big tables that you want
> vacuum to not get too aggressive on, but a few small tables that are
> highly volatile. So you want *them* vacuumed really fast to prevent
> them becoming huge tables with only a few rows therein, but your
> system might not be able to handle *all* your tables being vacuum
> full speed.

I meant setting cost limit to 0 *for those tables* only, not for all of
them.

Anyway it seems to me maybe there is room for a new table storage
parameter, say autovacuum_do_balance which means to participate in the
balancing program or not.

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


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers