Michael Ludwig schrieb am 11.05.2010 um 18:10:42 (+0200):

> Ann W. Harrison schrieb am 10.05.2010 um 20:38:10 (-0400):

> > > Second point of interest, what kind of indexes and with what
> > > directionality are used to back up the following CONSTRAINTs:
> > >
> > > * PRIMARY KEY
> > > * FOREIGN KEY
> > > * UNIQUE
> >
> > Ascending
>
> So does the general advice of creating a DESCENDING INDEX for
> queries looking for high values apply here?

Answering my own question: Yes.

> Might it be worth while creating an additional DESCENDING INDEX in any
> of these three cases?

Also yes. Just found it confirmed here:

http://tech.groups.yahoo.com/group/firebird-support/message/105190?o=0&var=1

Simple test script to show plans:

\,,,/
(o o)
------oOOo-(_)-oOOo------
create table ttpkix (id integer primary key, name varchar(10));
commit;

insert into ttpkix values (1, 'eins');
insert into ttpkix values (2, 'zwei');
insert into ttpkix values (3, 'drei');
commit;

set plan on;

select min(id) from ttpkix;
select max(id) from ttpkix;

create descending index tt_pk_desc on ttpkix(id);
commit;

select min(id) from ttpkix;
select max(id) from ttpkix;
-------------------------

--
Michael Ludwig