Richard Frith-Macdonald <richard@tiptree.demon.co.uk> writes:
> What has confused me is why a query using an empty index should be
> slow, irrespective of the state of the table that the index applies to.
Is it actually empty, or have you just deleted-and-not-yet-vacuumed
all the rows in the index?
I had hoped to see comparative EXPLAIN ANALYZE output for the fast and
slow cases. Maybe when it gets slow again you could redo the explain.
regards, tom lane