Joe,
> Adding an interval to a timestamp produces the expected result:
>
> cal=> select timestamp without time zone 'jan 1, 1999 00:00:00' +
> interval '1 month';
> ?column?
> ---------------------
> 1999-02-01 00:00:00
> (1 row)
>
> But reversing the two produces nonsense: is this because the values
> are implicitly cast to type of the leftmost term in the expression?
No. It's a bug. The expression interval + timestamp was accidentally
left undefined in PostgreSQL 7.2.
You can fix it by using a CREATE OPERATOR statement to define Interval
+ timestamp.
-Josh Berkus
