"Marc G. Fournier" <scrappy(at)postgresql(dot)org> writes:
> But, ti will if I try 'priority = -2' ... what is teh threshhold for using
> the index? obviously 10% of the records is too high ...
Depends on a lot of factors, but usually somewhere between 1% and 10%.
(The new bitmap index scan code in 8.1 should be workable for higher
percentages.) If this doesn't seem to square with reality for you,
you might try reducing random_page_cost.
regards, tom lane