force index problem in 8.4.1

Hi there,

I tried to force query to use index by specifying high execution cost, but
without success, even seqscan cost doesn't changed. This is 8.4.1

=# explain select count(*) from spots where coordinates <@ '(0,0),(0.1,0.1)'::box;                             QUERY
PLAN
 
-------------------------------------------------------------------- Aggregate  (cost=26620.84..26620.85 rows=1
width=0)  ->  Seq Scan on spots  (cost=0.00..25328.12 rows=517085 width=0)         Filter: (coordinates <@
'(0.1,0.1),(0,0)'::box)
(3 rows)

Time: 1.944 ms
=# alter FUNCTION pt_contained_box(point, box) COST 10000;
ALTER FUNCTION
Time: 369.800 ms
=# explain select count(*) from spots where coordinates <@ '(0,0),(0.1,0.1)'::box;                             QUERY
PLAN
 
-------------------------------------------------------------------- Aggregate  (cost=26620.84..26620.85 rows=1
width=0)  ->  Seq Scan on spots  (cost=0.00..25328.12 rows=517085 width=0)         Filter: (coordinates <@
'(0.1,0.1),(0,0)'::box)
(3 rows)

Time: 0.891 ms

    Regards,        Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83