prefer-pg18-not-null-not-valid

What It Detects

On PG18+, use native SET NOT NULL NOT VALID instead of the CHECK constraint workaround.

Why It's Dangerous

PostgreSQL 18 introduced ALTER TABLE ... SET NOT NULL NOT VALID, which marks a column NOT NULL without scanning the table. The old workaround of adding a CHECK (col IS NOT NULL) NOT VALID constraint is no longer needed.

Bad Example

-- PG18+: old workaround, no longer needed
ALTER TABLE users ADD CONSTRAINT users_email_nn
  CHECK (email IS NOT NULL) NOT VALID;
ALTER TABLE users VALIDATE CONSTRAINT users_email_nn;

Good Example

-- PG18+ native approach (simpler):
ALTER TABLE users ALTER COLUMN email SET NOT NULL NOT VALID;
ALTER TABLE users VALIDATE NOT NULL email;

Configuration

Disable this rule:

# .migrationpilotrc.yml
rules:
  MP081: false

Or change its severity:

# .migrationpilotrc.yml
rules:
  MP081:
    severity: warning