pg.ddx.io  pgsql-performance@postgresql.org mailing list archive  

help / color / mirror / Atom feed
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: Greg Smith <gsmith@gregsmith.com>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: I/O on select count(*)
Date: Thu, 15 May 2008 12:19:14 -0400
Message-ID: <6227.1210868354@sss.pgh.pa.us> (raw)
In-Reply-To: <20080515154932.GB8221@alvh.no-ip.org>
References: <920841.71690.qm@web44808.mail.sp1.yahoo.com>
	<482B1D5F.EE98.0025.0@wicourts.gov>
	<Pine.GSO.4.64.0805142133250.27290@westnet.com>
	<20080515020553.GN9838@alvh.no-ip.org>
	<Pine.GSO.4.64.0805142211300.5617@westnet.com>
	<2e78013d0805141940x50c3f51u439019e8e592959@mail.gmail.com>
	<Pine.GSO.4.64.0805142254080.10990@westnet.com>
	<20080515144106.GA8221@alvh.no-ip.org>
	<482C53A6.2030802@enterprisedb.com>
	<20080515154932.GB8221@alvh.no-ip.org>

Alvaro Herrera <alvherre@commandprompt.com> writes:
> Heikki Linnakangas escribió:
>> We know what kind of a relation we're dealing with in ReadBuffer, so we  
>> could add a flag to BufferDesc to mark heap pages.

> Hmm, I was thinking that it would need access to the catalogs to know
> where the tuples are, but that's certainly not true, so perhaps it could
> be made to work.

The issue in my mind is not so much could bgwriter physically do it
as that it's a violation of module layering.  That has real
consequences, like potential for deadlocks.  It'll become particularly
pressing if we go forward with the plans to get rid of the separate
dedicated buffers for pg_clog etc and have them work in the main
shared-buffer pool.

			regards, tom lane



view thread (54+ messages)  latest in thread

Message-ID: <6227.1210868354@sss.pgh.pa.us>
Permalink:  ../6227.1210868354@sss.pgh.pa.us/
Also on:    postgresql.org/message-id/6227.1210868354@sss.pgh.pa.us

 · 

reply
Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: pgsql-performance@postgresql.org
  Cc: tgl@sss.pgh.pa.us, alvherre@commandprompt.com, heikki@enterprisedb.com, gsmith@gregsmith.com, pavan.deolasee@gmail.com
  Subject: Re: I/O on select count(*)
  In-Reply-To: <6227.1210868354@sss.pgh.pa.us>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox