POSTGRESQL Optimizer

I wonder how i can enforce the PostgreSQL optimizer in order to use the
indexes in cases of SQL queries with comparison (<,>) and not equality. I
create a table with 4 attributes, the two of them are types of integer8 in
PostgreSQL and i create to those 2 indexes (which by default are B+trees).
However they didn't work. I would appreciate any comment.



                                                 SWTHRHS TOYRTOYNHS
                                                (tourtoun@csd.uch.gr)