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Re: [HACKERS] Docs off on ILIKE indexing?

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Magnus Hagander <mha(at)sollentuna(dot)net>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-docs(at)postgresql(dot)org
Subject: Re: [HACKERS] Docs off on ILIKE indexing?
Date: 2006-01-17 20:26:39
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Lists: pgsql-docspgsql-hackers
On Tue, Jan 17, 2006 at 03:44:30PM +0100, Magnus Hagander wrote:
> > >
> > > 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(at)pervasive(dot)com
Pervasive Software    work: 512-231-6117
vcard:       cell: 512-569-9461

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