Pavel Hlavnicka <pavel(at)gingerall(dot)cz> writes:
> I use 7.2.1. :(
7.2 certainly will fold "'now'::timestamp - '1 hour'::interval" to a
timestamp constant. This could be a datatype compatibility issue
(is created_at the same type? in particular, with/without time zone?)
or it could be a selectivity issue --- ie, the planner might think the
condition covers too much of the table to make the index useful.
It would be useful to look at the results of EXPLAIN ANALYZE for this
query, with and without ENABLE_SEQSCAN turned off.
regards, tom lane