I personally find more uses for the normal uniqueness property of NULL, but it’s always nice to have more freedom to specify the constraints that are useful for your application.
I recently used this and it’s a great idea if you can’t go to higher normal forms.
Unfortunately REPLICA IDENTITY cannot use this kind of index; it complains about nullable columns, even though it should theoretically be OK.
Does anyone know if that’ll be supported one day?
I’d post that on the mailing list, rather than here, but please let us know if you find out. :)