Re: Check constraints on non-immutable keys

Peter Eisentraut <peter_e@gmx.net> writes:
> <kibo>
> "The <search condition> shall simply contain a <boolean value
> expression> that is retrospectively deterministic."

> This is then defined in a rather complex manner that ends up disallowing
> col > now() but allowing col < now().
> </kibo>

Oh, cute.  Seems to have been added in SQL:2003.  I guess somebody
nagged them about wanting to be able to write CHECK(col <= now()).
The detailed definition is amazingly laborious and yet limited, though,
as it basically doesn't address the problem except for that specific
case and close relatives.
        regards, tom lane