About index ...

Hello,

First, excuse me for my english. I have 33 tables ( with millions rows ) and
for most tables i use btree index. My problem is when
i use explain directive. In fact btree index work only
with operator "=" . eg: select * from test where id = 45
EXPLAIN
Index scan using idx_id on test
an doesn't work with select * from test where id < 45.
EXPLAIN
Seq scan on test
Why ???

Thanks