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From: Bill Moran <wmoran@collaborativefusion.com>
To: Dave Dutcher <dave@tridecap.com>
Cc: 'SPMLINGAM' <spmlingam@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: postgresql performance
Date: Wed, 5 Mar 2008 11:00:13 -0500
Message-ID: <20080305110013.68f1e08a.wmoran@collaborativefusion.com> (raw)
In-Reply-To: <01b501c87eca$8da00ff0$8e00a8c0@tridecap.com>
References: <15847165.post@talk.nabble.com>
	<01b501c87eca$8da00ff0$8e00a8c0@tridecap.com>

In response to "Dave Dutcher" <dave@tridecap.com>:

> > -----Original Message-----
> > From: SPMLINGAM
> > Subject: [PERFORM] postgresql performance
> > 
> > Dear Friends,
> >      I have a table with 50 lakhs records, the table has more 
> > then 10 fields, i have primary key, i have select query with 
> > count(*) without any condition, it takes 17 seconds.
> 
> 17 seconds to scan 5 million records doesn't sound that bad to me.
> Postgresql does not store a count of records, and so it has to actually scan
> the table to count all the records.  This was a design choice because select
> count(*) isn't usually used in a production system.  

Note that if you need a fast count of the number of rows in a large
table, there are known workarounds to get it.  Such as creating triggers
that update a count column, or using explain to get a quick estimate of
the number of rows (if that's acceptable).

-- 
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran@collaborativefusion.com
Phone: 412-422-3463x4023

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