Re: Lower case

On Thu, 27 Jan 2005 00:16:14 +0000, Vladimir S. Petukhov
<vladimir@sycore.org> wrote:
> > > LC_COLLATE:                           ru_RU
> > > LC_CTYPE:                             ru_RU
> > >    Name    |  Owner   | Encoding
> > > -----------+----------+----------
> > >  testdb   | postgres | UNICODE
> > > And LIKE, ILIKE, ~ do not recognize upper/lower case..
> >
> > What character encoding is implied by those LC_ settings on your machine?
> > If it's different from the database encoding (here utf8) these things
> > won't actually work right.
> LANG=ru_RU.koi8r
> LC_ALL=ru_RU.koi8r
> But how it act on lower/upper cases? Client use utf-8 encoding...

The client uses utf-8 encoding, so does server.  Texts are stored
using UTF-8.  However when you call a lower() function from
PostgreSQL it does more or less following:
  -- it retrieves text row from database.  This text is in UTF-8 encoding.
  -- it calls strxfrm function upon this text.
     -- strxfrm function sees that current locale is ru_RU.koi8r
     -- strxfrm then takes utf-8 encoded text and treats it as koi8r
     -- strxfrm "skips over" characters it does not recognize (utf-8 chars)
     -- strxfrm returns transformed text
  -- PostgreSQL takes the resulting text, believing it is still in utf-8.
In other words, probably only latin characters were subject to lower()
functions, any "unknown" Russian UTF-8 characters were at best
skipped.

Please note that PostgreSQL does not do implicit utf8->koi8r->utf8
conversion while calling function lower().  AFAIK it does not even
know (or care) if current locale setting ("ru_RU") is for different
encoding than current database's.  It is DB Admin's duty to make
sure cluster locale (done in initdb) is compatible with database
encoding (done in createdb).

  Regards,
      Dawid