The old "not using index" question

Hi there,

---this one is using the index on "ranking"
SELECT *
FROM ttm_slots s
WHERE s.peering = 72
AND s.ranking = 1050

---but this one does not?
SELECT *
FROM ttm_slots s
WHERE s.peering = 72
AND s.ranking < 1050
AND s.ranking > 950

The index ist "btree", so it should be able to use the index with a < >
comparison?

\d ranking_ttm_slots_key
Index "ranking_ttm_slots_key"
Column | Type
---------+---------
ranking | integer
btree

regards,
Jan-Philipp