Thread

Re: match_special_index_operator don't work in 7.2.1

Andriy I Pilipenko <bamby@marka.net.ua> — 2002-05-19T11:18:12Z

On Sun, 19 May 2002, Stephan Szabo wrote:

>
> On Sun, 19 May 2002, Andriy I Pilipenko wrote:
>
> > Please enter a FULL description of your problem:
> > ------------------------------------------------
> >
> > I've upgraded from 7.0.3 to 7.2.1 and noticed that queries like
> >
> > SELECT ... WHERE field LIKE 'something%'
> >
> > take too much time to execute now.
>
> Are you sure that you're running in C locale?  If you're unsure,
> you can build pg_controldata in contrib and check.

Thanks for the point - I missed that. I'm running KOI8 locale now and used
C locale in old database.

> (From comments in recent sources:
> /*
>  * We want test whether the database's LC_COLLATE setting is safe for
>  * LIKE/regexp index optimization.
>  *
>  * The key requirement here is that given a prefix string, say "foo",
>  * we must be able to generate another string "fop" that is greater
>  * than all strings "foobar" starting with "foo".  Unfortunately, a
>  * non-C locale may have arbitrary collation rules in which "fop" >
>  * "foo" is not sufficient to ensure "fop" > "foobar".  Until we can
>  * come up with a more bulletproof way of generating the upper-bound
>  * string, the optimization is disabled in all non-C locales.
>  *
>  * (In theory, locales other than C may be LIKE-safe so this function
>  * could be different from lc_collate_is_c(), but in a different
>  * theory, non-C locales are completely unpredicable so it's unlikely
>  * to happen.)
>  */
> )

  Kind regards,
  Andriy I Pilipenko
  PAI1-RIPE