<ul><li>In PostgreSQL 17 and earlier versions, NOT NULL constraints are enforced immediately upon creation.</li><li>To bypass the constraint, users had to drop it and then re-add it after loading data.</li><li>PostgreSQL 18 introduces the ability to add NOT NULL constraints as NOT VALID.</li><li>This allows data loading even if constraints would initially be violated.</li><li>Constraints added as NOT VALID will not be enforced until validation occurs.</li><li>The new feature provides flexibility for data loading and constraint management.</li><li>Users can manually fix data inconsistencies before validating constraints.</li><li>PostgreSQL 18 now supports adding constraints as NOT VALID for better control.</li><li>This enhancement streamlines the process of loading data with constraints.</li><li>Users can now add NOT NULL constraints that are deferred until validation.</li></ul>

PostgreSQL 18: Allow NOT NULL constraints to be added as NOT VALID

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