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Re: UTF8MatchText

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: Dennis Bjorklund <db(at)zigo(dot)dhs(dot)org>, ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, Bruce Momjian <bruce(at)momjian(dot)us>, pgsql-patches(at)postgresql(dot)org
Subject: Re: UTF8MatchText
Date: 2007-05-20 21:50:44
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Lists: pgsql-hackerspgsql-patches
Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> Yeah, quite possibly. I'm also wondering if we are wasting effort 
> downcasing what will in most cases be the same pattern over and over 
> again. Maybe we need to look at memoizing that somehow, or at least test 
> to see if that would be a gain.

Someone (Itagaki-san IIRC) suggested that we ought to convert
"x ILIKE y" into "lower(x) LIKE lower(y)" at some fairly early
stage, definitely before constant-folding in the planner.  That
would take care of that issue without any run-time mechanism,
and would open opportunities for making use of an index on lower(x).

I recall thinking at the time that there were some potential downsides,
but right at the moment I'm darned if I can see any --- especially
if we're going to make ILIKE do this uniformly at runtime anyway.

			regards, tom lane

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