Thank you!. Problem is, my application can query the database using a combination of more than 100 conditions from 18 diferent tables. Users can combine conditions in thousands of ways, so I can't build the perfect query for each case.

Also, exaclty the same query system have to work over Firebird, Oracle and PostgreSQL. So it is much more dificult for me to do the pefect query for each case.

Anyway, my queries are all very acceptable in performance, but, something changed in late 2.5 updates making this query to go from 1 minute to 20 minutes to finish.

On PostgreSQL and Oracle, this query is going still very well.

Thank you!