Optimize query on timestamp column in Postgresql 8.x

Lets suppose you have and orders table, this table contains a timestamp column indicating the creation time of the orde开发者_JAVA百科rs. A normal query would be to obtain the orders between two dates. Does anybody know how to optimize this query because creating an index on the timestamp column has no effect as shown by EXPLAIN ANALYZE.

Usually indexes are used, but only if the table is properly analyzed (VACUUM ANALYZE or just ANALYZE), and if the table size is large enough that index scans are faster than sequential scans.

An index should work. I suspect its not working for you because your table is either tiny (PostgreSQL almost never uses indices for tiny tables), or you haven't done an analyze on it.