Re: varchar sort ordering ignore blanks

On Sunday 20 January 2008 01:07, Tom Lane wrote:
> "Luca Arzeni" <l(dot)arzeni(at)amadego(dot)com> writes:
> > Is there any way to consider blanks meaningfull AND sort properly locale
> > specific vowels ?
>
> This isn't a Postgres question, it's a locale question. (If you try,
> you'll find that sort(1) sorts the same as we do in any given locale.)
>
> I imagine you could create a custom locale definition that acts this
> way, but I have no idea about the degree of wizardry involved.
> "man localedef" would probably be a place to start.
>
> If you come up with a reasonably simple recipe for this, please post
> it here, as you're not the first to have asked and you likely won't
> be the last ...
>
> regards, tom lane

Thanks Tom,
I gave a look at localedef, but it seems too much complex for my
understanding.

I understood that (under debian etch) lc_collate is defined for posix in file:
/usr/share/i18n/locales/POSIX

Here actually I can find an undestandable LC_COLLATE directive that defines
all chars one after the other in ASCII order. Thats fine.

Then I looked at it_IT locale definition and noticed that this locale (and
many if not all other locales, as far as I can see) have a collation order
inherited from the file:
/usr/share/i18n/locales/iso14651_t1

This seems to be a iso standard, but it is not easily understandable by me. It
includes macros and defines also sorting for many character sets, including
arabic and grec.

I think I've found the problem (space is actually ignored and put in a
separate list from other chars), but I'm not able to understand what shoud be
the proper value to put in the row.

At line 537 I can read the following lines:
order_start <SPECIAL>;forward;backward;forward;forward,position
#
# Tout caractère non précisément défini sera considéré comme caractère spécial
# et considéré uniquement au dernier niveau.
#
# Any character not precisely specified will be considered as a special
# character and considered only at the last level.
# <U0000>......<U7FFFFFFF> IGNORE;IGNORE;IGNORE;<U0000>......<U7FFFFFFF>
#
# SYMB. N° GLY
#
<U0020> IGNORE;IGNORE;IGNORE;<U0020> # 32 <SP>

so I guess space is beeing ignored.

At line 810 I can read:
<U2079> <9>;<BAS>;<EMI>;IGNORE # 197 <9S>
#
<U0061> <a>;<BAS>;<MIN>;IGNORE # 198 a
<U00AA> <a>;<PCL>;<EMI>;IGNORE # 199 ª
<U00E1> <a>;<ACA>;<MIN>;IGNORE # 200 á
<U00E0> <a>;<GRA>;<MIN>;IGNORE # 201 à
<U00E2> <a>;<CIR>;<MIN>;IGNORE # 202 â
<U00E3> <a>;<TIL>;<MIN>;IGNORE # 203 ã
<U00E4> <a>;<REU>;<MIN>;IGNORE # 204 ä
<U00E5> <a>;<RNE>;<MIN>;IGNORE # 205 å

So my guess is that if I could put properly the space AFTER the commented line
and before the linte that starts with <U0061> (that is, before the lower "a")
I could solve the problem.

May be that some locale wizard is listening around and can help me?

Thanks, Luca

--
Ing. Luca Arzeni
Amadego S.R.L.
tel.: 02 6193672
cell.: 339 8350298
mailto: l(dot)arzeni(at)amadego(dot)com

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