Date: Tue, 17 Jan 2006 14:26:39 -0600
From: "Jim C. Nasby" <jnasby@pervasive.com>
To: Magnus Hagander <mha@sollentuna.net>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-docs@postgresql.org
Subject: Re: [HACKERS] Docs off on ILIKE indexing?
Message-ID: <20060117202639.GL67693@pervasive.com>
References: <6BCB9D8A16AC4241919521715F4D8BCE6C7EB6@algol.sollentuna.se>
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On Tue, Jan 17, 2006 at 03:44:30PM +0100, Magnus Hagander wrote:
> > > http://www.postgresql.org/docs/8.1/static/indexes-types.html
> > > says:
> > > The optimizer can also use a B-tree index for queries involving the 
> > > pattern matching operators LIKE, ILIKE, ~, and ~*, if the 
> > pattern is a 
> > > constant and is anchored to the beginning of the string - 
> > for example, 
> > > col LIKE 'foo%' or col ~ '^foo', but not col LIKE '%bar'.
> > 
> > > But really, does it use indexes for ILIKE?
> > 
> > That's pretty poorly phrased.  For ILIKE it'll only work if 
> > there's a prefix of the pattern that's not letters (and hence 
> > is unaffected by the case-folding issue).
> 
> Ahh. That explains it. Perfectly logical.
> And yes, that's pretty poorly phrased - at least I didn't understand it
> :-)

I was going to submit a patch on this, and the best way seems to be
adding a note to 'ILIKE', specifying that it will only work if there's a
prefix to the pattern that isn't letters. Is there a standard way to tag
a word indicating that there's a note?
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461