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Message-ID: <4e96c6600608221121p2afc603bx90fcf879aab47d96@mail.gmail.com>
Date: Tue, 22 Aug 2006 20:21:23 +0200
From: "Thomas Samson" <koollman@gmail.com>
To: "Ulrich Habel" <espero7757@gmx.net>, pgsql-performance@postgresql.org
Subject: Re: query planner: automatic rescribe of LIKE to BETWEEN ?
In-Reply-To: <20060822174539.GD25475@alvh.no-ip.org>
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References: <200608221922.59734.espero7757@gmx.net>
	<20060822174539.GD25475@alvh.no-ip.org>

On 8/22/06, Alvaro Herrera <alvherre@commandprompt.com> wrote:
> Ulrich Habel wrote:
> > Hello all,
> > had an idea of optimizing a query that may work generally.
> >
> > In case a 'column' is indexed, following two alterations could be done
> > I think:
> >
> > A)
> >
> >   select ... where column ~ '^Foo'     -->  Seq Scan
>
> This is not true.  You can make this query use an index if you create it
> with opclass varchar_pattern_ops or text_pattern_ops, as appropiate.
>
> Thus you don't need any hack here.
>

And in the case of more general expression, like:
 select ... where column ~ 'something';

Is there a way to optimise this ? (in the case where 'something' is not
a word, but a part of a word)

-- 
Thomas SAMSON