From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: Willo van der Merwe <willo@studentvillage.co.za>
To: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL performance issues
Date: Tue, 29 Aug 2006 17:15:33 +0200
Message-ID: <20060829151533.GA7586@localhost.localdomain> (raw)
In-Reply-To: <44F4554F.40906@studentvillage.co.za>
References: <44F446B2.2090900@studentvillage.co.za>
<20060829144636.GA6796@localhost.localdomain>
<44F4554F.40906@studentvillage.co.za>
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
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: andreas.kretschmer@schollglas.com, willo@studentvillage.co.za
Subject: Re: PostgreSQL performance issues
In-Reply-To: <20060829151533.GA7586@localhost.localdomain>
* 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