On Tue, Nov 02, 2010 at 12:04:42PM +0100, Cédric Villemain wrote:
> 2010/11/2 hubert depesz lubaczewski <depesz@depesz.com>:
> > On Mon, Nov 01, 2010 at 02:57:56PM +0100, Cédric Villemain wrote:
> >> > CONSTRAINT tableindex_pkey PRIMARY KEY (tableindex)
> >> > )
> >> > the index definition is
> >> > CREATE INDEX "PK_AT2"
> >> > ON ABC
> >> > USING btree
> >> > (event, tableindex)
> >> > TABLESPACE sample;
> >>
> >> Indexing twice the same column is useless. (perhaps move your PK to
> >> the tablespace 'sample' is good too ?)
> >
> > why do you say that?
> > these are not the same indexes and they serve different purposes.
>
> Given that tableindex is the PK column, I really like to now the usage
> pattern for having it indexed twice.
select * from table where event = 123 order by tableindex desc limit 50;
Best regards,
depesz
--
Linkedin: http://www.linkedin.com/in/depesz / blog: http://www.depesz.com/
jid/gtalk: depesz@depesz.com / aim:depeszhdl / skype:depesz_hdl / gg:6749007
