Slow query using simple equality operators

Can anybody explain to me why this query is executing so slow?

=# explain select s_content,textdir from text_search where
path_id='1' AND tb_id='P2_TB00001';
QUERY PLAN
------------------------------------------------------------------------
-------------------------
Bitmap Heap Scan on text_search (cost=39861.94..59743.55 rows=5083
width=36)
Recheck Cond: ((path_id = 1) AND (tb_id = 'P2_TB00001'::text))
-> BitmapAnd (cost=39861.94..39861.94 rows=5083 width=0)
-> Bitmap Index Scan on idx_search_path_id
(cost=0.00..16546.09 rows=1016571 width=0)
Index Cond: (path_id = 1)
-> Bitmap Index Scan on idx_search_tb_id
(cost=0.00..23315.60 rows=1016571 width=0)
Index Cond: (tb_id = 'P2_TB00001'::text)
(7 rows)

Thanks in advance!

Benjamin