PostgreSQL NOT VALID Constraints Separate Enforcement from Table Scans

Tue, 15 Sep 2026 00:00:00 +0700

Adding a constraint to a populated PostgreSQL table can combine two distinct jobs: establish enforcement for future writes and prove that every existing row already satisfies the rule. NOT VALID separates those jobs for foreign-key and check constraints. The constraint becomes active for later inserts and updates, while verification of older rows is deferred.

That separation changes the locking profile of a schema migration without changing the intended final constraint. It also creates a temporary catalog state in which PostgreSQL enforces the rule but has not yet established that all stored rows satisfy it.

DDL on Nalar

PostgreSQL NOT VALID Constraints Separate Enforcement from Table Scans