Re: [HACKERS] LIKE fixed(?) for non-ASCII collation orders - Mailing list pgsql-hackers

From Andreas Degert
Subject Re: [HACKERS] LIKE fixed(?) for non-ASCII collation orders
Date
Msg-id 87vh5fgnvq.fsf@tarzan.noname.
Whole thread Raw
In response to LIKE fixed(?) for non-ASCII collation orders  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: [HACKERS] LIKE fixed(?) for non-ASCII collation orders
Re: [HACKERS] LIKE fixed(?) for non-ASCII collation orders
List pgsql-hackers
Tom Lane <tgl@sss.pgh.pa.us> writes:

> I have just committed what I hope is the final solution for the problem
> of LIKE index optimization in non-ASCII locales.  indxpath.c now
> generates both a lower and upper indexqual in all locales.  For example,
>     x LIKE 'foo%t'
> will create indexqual conditions
>     x >= 'foo' AND x < 'fop'
> The "<" condition is omitted only if the code is unable to produce a
> string greater than the pattern's constant prefix.

the .. >= .. < .. condition will result in addtional matches, like 'fo ot',
so you still have to check with LIKE. I'm using such an expression
(without the additional LIKE) in an application, and it seems to match 
at least everything that LIKE would match too (my users would have
complained about missing matches, but i never did a formal test or
evaluation).


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