Andrei Ivanov <andrei.ivanov@ines.ro> writes:
> The table contains ~140 rows and I've ran vacuum full analyze.
On a table that small, a seqscan is usually preferable because it takes
less I/O. In your test case the index pages were evidently already in
RAM, so that no additional I/O was actually needed to consult the index
--- but in a production situation you'd not be able to count on that.
regards, tom lane