Re: WIP: generalized index constraints

On Sun, 2009-09-20 at 10:08 -0700, Jeff Davis wrote:
> On Sun, 2009-09-20 at 13:01 -0400, Tom Lane wrote:
> > The current infrastructure for deferred uniqueness requires that the
> > thing actually be a constraint, with an entry in pg_constraint that
> > can carry the deferrability options.  So unless we want to rethink
> > that, this might be a sufficient reason to override my arguments
> > about not wanting to use CONSTRAINT syntax.
> 
> Ok. Using the word EXCLUSION would hopefully guard us against future
> changes to SQL, but you know more about the subtle dangers of language
> changes than I do.
> 
> So, do I still omit it from information_schema?

I would say yes.

Overall, I think this terminology is pretty good now.  We could say,
PostgreSQL has a new constraint type, exclusion constraint.  It shares
common properties with other constraint types, e.g., deferrability (in
the future), ADD/DROP CONSTRAINT, etc.  But because the standard does
not describe exclusion constraints, they are not listed in the
information schema.