types & index usage

Hi!

I have a table with year, month, day and hour fields (all SMALLINT
type). Selecting one row from it takes about 40 msecs, and I am
trying now to use DATE type instead of first three fields.

Now select time decreased to less than millisecond, but I found that i
must use this form: hour=10::smallint instead of simple hour=10,
because in the latter case PostgreSQL does sequential scan.

I've heard something about type coercion issues, so I just want to say
that it is very funny to see such sort of things...