On 30th of June, Alvaro Herrera committed patch:
Enable CHECK constraints to be declared NOT VALID This means that they can initially be added to a large existing table without checking its initial contents, but new tuples must comply to them; a separate pass invoked by ALTER TABLE / VALIDATE can verify existing data and ensure it complies with the constraint, at which point it is marked validated and becomes a normal part of the table ecosystem. An non-validated CHECK constraint is ignored in the planner for constraint_exclusion purposes; when validated, cached plans are recomputed so that partitioning starts working right away. This patch also enables domains to have unvalidated CHECK constraints attached to them as well by way of ALTER DOMAIN / ADD CONSTRAINT / NOT VALID, which can later be validated with ALTER DOMAIN / VALIDATE CONSTRAINT. Thanks to Thom Brown, Dean Rasheed and Jaime Casanova for the various reviews, and Robert Hass for documentation wording improvement suggestions. This patch was sponsored by Enova Financial.