pg_dump and ALTER TABLE / ADD FOREIGN KEY

With the pg_depend / pg_constraint implementation foreign keys are
applied to dumps via alter table / add foreign key (retains inter
table dependencies).

Some have expressed that this could be quite slow for large databases,
and want a type of:

SET CONSTRAINTS UNCHECKED;

However, others don't believe constraints other than foreign keys
should go unchecked.

That said, is this functionality wanted outside of pg_dump /
pg_restore?

Or would the below be more appropriate?:
ALTER TABLE tab ADD FOREIGN KEY .... TRUST EXISTING DATA;

That is, it will not check pre-existing data to ensure it's proper.
The assumption being that pg_dump came from an already consistent
database. Needs better wording.

--
Rod