Skip site navigation (1) Skip section navigation (2)

Re: I/O on select count(*)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: I/O on select count(*)
Date: 2008-05-15 16:19:14
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Heikki Linnakangas escribi:
>> 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

In response to

pgsql-performance by date

Next:From: Subbiah Stalin-XCGF84Date: 2008-05-15 16:28:19
Subject: Re: Update performance degrades over time
Previous:From: Guillaume CottenceauDate: 2008-05-15 15:56:31
Subject: Re: which ext3 fs type should I use for postgresql

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group