deferrable check, trigger

Hi!

I has needed deferrable constraint CHECK, but i'm sorry, because it has
not implemented.
I has studied the postgresql source code, and i think there are three
possibilities in implementation:

1. implementing deferrable check. It is not easy (there is no deferred
constraint manager), but it is corresponds to current sql syntax of
postgresql.
2. allow deferrable triggers for all type of triggers (or at least for
after trigger). I thing it is easier to do, because it exists, but
limited for a special kind of trigger. The problem of this solution is,
that is not corresponds to current sql syntax.
I prefer this, because of the deferrable trigger is very useful
(checking of deferrable unique constraint, etc...)

3. implement deferrable check at sql level, but deferred after trigger
at inner level. (like foreign key implementation)

What is about this?

Horváth Sándor