add-migration

To make Alembic migrations idempotent, implement existence checks for tables, columns, indexes, and enums so they only execute when missing. This ensures safe re-runs during CI-driven rollouts without breaking environments.

Safely adding PostgreSQL enum values requires handling transaction caveats and using create_type=False patterns in SQLAlchemy. This prevents deployment errors by ensuring the enum type is not unnecessarily recreated during schema adjustments.

Handling partial unique indexes in PostgreSQL migrations involves using specific PostgreSQL-style SQL within your Alembic upgrade logic. This approach safely manages index creation by incorporating existence checks to avoid duplicate indexing errors.

An Alembic migration needs a downgrade path for CI-driven deployments to ensure operational readiness. Including a downgrade function allows you to safely revert schema changes if the deployment encounters unexpected issues.

To test if a database migration is repeatable, apply the migration and then re-run it to confirm the second execution becomes a no-op. This verifies the idempotent upgrade logic correctly handles existing schema elements.