Subject: Re: Indexes with descending date columns
From: Theo Kramer <theo@flame.co.za>
Reply-To: theo@flame.co.za
To: pgsql-performance@postgresql.org
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Date: Fri, 24 Mar 2006 06:32:29 +0200
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On Thu, 2006-03-23 at 16:16, Alvaro Herrera wrote:
> Theo Kramer wrote:
> 
> > All good input - thanks, however, before I start messing with my stuff
> > which I know will be complex - some questions to any of the developers
> > on the list.
> > 
> > i  Is it feasible to extend index creation to support descending 
> >    columns? ... this is supported on other commercial and non
> >    commercial databases, but I do not know if this is a SQL standard.
> 
> This can be done.  You need to create an operator class which specifies
> the reverse sort order (i.e. reverse the operators), and then use it in
> the new index.

Hmmm, would that then result in the following syntax  being valid?

  create index my_idx on my_table (c1, c2 desc, c3, c4 desc) ;

where my_table is defined as

  create table my_table (
    c1 text,
    c2 timestamp,
    c3 integer,
    c4 integer
  );

If so, I would appreciate any pointers on where to start on this -
already fumbling my way through Interfacing Extensions To Indexes in the
manual...

Regards
Theo
-- 
Regards
Theo