On Mon, 2 Feb 2004, Tomasz Myrta wrote:
> Dnia 2004-02-02 15:46, U?ytkownik Rigmor Ukuhe napisa3:
> > Hi,
> >
> > I have many indexes somehow overlaping like:
> > ... btree ("STATUS", "VISIBLE", "NP_ID");
> > ... btree ("STATUS", "VISIBLE");
> >
> > is perfomance gained by "more exact" index worth overhead with managing
> > indexes.
>
> The second (2 columns) index is useless - it's function is well done by
> the first one (3 columns).
Not entirely, since it only has to sort two columns, it will be smaller,
and will therefore be somewhat faster.
On the other hand, I've seen a lot of folks create multi column indexes
who didn't really understand how they work in Postgresql.
