deferred check constraints

[Perry Smith <pedz@xxxxxxxxxxxxxxxx>]

Right now, it would be nice if I could get a check constraint to be  
deferred.  Its a long story.  I want a circular constraint.  The way  
things are set up right now, it would be easy if I could defer my  
check constraint.  I'm doing a polymorphic relation.  One direction  
is a simple reference a fixed table.  The other direction is a  
reference to table that changes based upon the type of the item.  I  
can do this check in a function which implies it is a check constraint.

I may figure out how to flip everything around so that the simple  
reference constraint could be deferred.  That is one option

The other option is to add deferred check constraints to PostgreSQL.   
I've never looked at the PostgreSQL code but I like parsers, etc.   
How hard would it be to add this to PostgreSQL and is it something of  
general interest or am I somewhat lost in the woods?

Thank you,
Perry