David Fetter <david@fetter.org> writes:
> He expected '-' to subtract seconds, just as '+' added them.
Ah. Well, what it boils down to is that in a scenario like
known_type_expr operator unknown_literal
we preferentially consider unknown_literal to be of the same type
as the other operand. But there's no timestamp plus timestamp
operator (doesn't seem like a sensible operation to me, does it
to you?), so there's only one possible typing of the unknown literal,
and it's not that. Plus and minus just aren't all that symmetrical
in this situation.
regards, tom lane