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From: Chris <dmagick@gmail.com>
To: Bert <clemens.bertschler@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Easy question
Date: Wed, 03 May 2006 16:21:23 +1000
Message-ID: <44584BE3.7020403@gmail.com> (raw)
In-Reply-To: <1146355679.311472.57800@u72g2000cwu.googlegroups.com>
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	<1146355679.311472.57800@u72g2000cwu.googlegroups.com>

Bert wrote:
> No i didn't defined any indexes for the table, I know the performance
> will increase with an index, but this was not my question. My question
> furthermore belongs to the access mode of the SQL statement.
> Furthermore i do not understand why the Upper function should increase
> the performance.

The index will have entries like:

CHRIS
BERT
JOE

and so on.

If you run a query like:

select * from table where UPPER(name) = 'CHRIS';

It's an easy match.

If you don't create an UPPER index, it has to do a comparison with each 
row - so the index can't be used because postgres has to convert the 
field to upper and then do the comparison.

-- 
Postgresql & php tutorials
http://www.designmagick.com/

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