Date: Tue, 29 Aug 2006 17:15:33 +0200
From: "A. Kretschmer" <andreas.kretschmer@schollglas.com>
To: Willo van der Merwe <willo@studentvillage.co.za>,
	pgsql-performance@postgresql.org
Subject: Re: PostgreSQL performance issues
Message-ID: <20060829151533.GA7586@localhost.localdomain>
References: <44F446B2.2090900@studentvillage.co.za>
	<20060829144636.GA6796@localhost.localdomain>
	<44F4554F.40906@studentvillage.co.za>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <44F4554F.40906@studentvillage.co.za>
User-Agent: Mutt/1.5.9i

am  Tue, dem 29.08.2006, um 16:55:11 +0200 mailte Willo van der Merwe folgendes:
> >>4 1/2 seconds for a count(*) ? This seems a bit rough - is there anything 
> >>else
> >>    
> >
> >Because of MVCC.
> >http://www.thescripts.com/forum/thread173678.html
> >http://www.varlena.com/GeneralBits/120.php
> >http://www.varlena.com/GeneralBits/49.php
> >
> >
> >Andreas
> >  
> Hi Andreas,
> 
> Thanks for your prompt reply. I understand why this is a sequential 
> scan, I'm just a bit perturbed that it takes 4.5 seconds to execute said 
> scan. The table is only 750,000 records big. What happens when this 
> table 7 million records big? Will this query then take 45 seconds to 
> execute?

How often do you need a 'select count(*) from big_table'?

I assume, not frequently. And if you need realy this, you can write a
trigger or read the statistics for the table.


Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47215,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net