The Idempotency Gap: Why Database Migrations Fail Twice

Supabase RLS policies lack native idempotency, causing migrations to crash when re-applied in CI environments, team onboarding, or rollback scenarios. By wrapping policy creation in PostgreSQL DO blocks with existence checks, developers can build resilient migrations that safely run multiple times without errors. This pattern is essential for modern development workflows involving automated testing, preview environments, and emergency hotfixes.