Date: Fri, 6 Sep 2013 01:22:36 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Robert Haas <robertmhaas@gmail.com>,
 Peter Geoghegan <peter@2ndquadrant.com>,
 Tom Lane <tgl@sss.pgh.pa.us>, Andrew Dunstan <andrew@dunslane.net>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [PERFORM] encouraging index-only scans
Message-ID: <20130906052236.GF6067@eldon.alvh.no-ip.org>
References: <15321.1355347953@sss.pgh.pa.us> <50C90154.8060103@dunslane.net>
 <50C904DB.9090305@dunslane.net> <20121213024837.GB22363@momjian.us>
 <23298.1355370698@sss.pgh.pa.us>
 <CAEYLb_U1dTg=bXkDL=yvFTrMw5oC13ivgZA=jdQXnbgaDJ+e-Q@mail.gmail.com>
 <20130904205655.GR21874@momjian.us>
 <20130906001437.GA29264@momjian.us>
 <CA+Tgmobh_-n-GvKX++DVctToZ9SZkdhvszP=CBjh9XZOvWsTEg@mail.gmail.com>
 <20130906020043.GH27195@momjian.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20130906020043.GH27195@momjian.us>
User-Agent: Mutt/1.5.21 (2010-09-15)
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Bruce Momjian escribió:

> Ideas
> -----
> 
> I think we need to detect tables that do not have VM bits set and try to
> determine if they should be vacuumed.  If a table has most of its VM
> bits set, there in need to vacuum it for VM bit setting.

I think it's shortsighted to keep thinking of autovacuum as just a way
to run VACUUM and ANALYZE.  We have already discussed work items that
need to be done separately, such as truncating the last few empty pages
on a relation that was vacuumed recently.  We also need to process a GIN
index' pending insertion list; and with minmax indexes I will want to
run summarization of heap page ranges.

So maybe instead of trying to think of VM bit setting as part of vacuum,
we could just keep stats about how many pages we might need to scan
because of possibly needing to set the bit, and then doing that in
autovacuum, independently from actually vacuuming the relation.

I'm not sure if we need to expose all these new maintenance actions as
SQL commands.

-- 
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