Re: Multilingual application, ORDER BY w/ different locales?

Palle Girgensohn <girgen@partitur.se> writes:
> I am dreaming of a SET LC_COLLATE or simliar command that will 
> only affect my session, not all other users.
> I know this is not implemented in postgres. How impossible is it to add 
> this feature, and what implications would pg suffer?

Actually, what the SQL spec suggests is that LOCALE be attached to
individual table columns.  A SET command to cause LOCALE to change
on the fly within a session is quite impractical: that would mean
that the sort ordering of existing columns changes, which would mean
that any indexes on those columns are broken.

Per-column LOCALE is on the to-do list.  In my mind the main difficulty
with it is that the standard C library doesn't really support concurrent
use of multiple locales: it's built around the assumption that you set
your locale once at program startup.  setlocale() is, typically, not
a fast operation.  To get around this it seems we'd need to write our
own set of locale library routines, which is a daunting amount of work.

I think the last time this came up, someone mentioned that there's an
open BSD-license locale library being worked on, which possibly we could
adapt instead of reinventing this wheel for ourselves.  But I don't
recall more than that.  Check the archives.
        regards, tom lane