database-migrations

To safely add a NOT NULL constraint, use a two-step Rails migration: backfill existing rows first, then add the constraint in a separate migration to avoid locking the PostgreSQL table during the update.

Zero-downtime index creation requires using the `concurrent` option in Rails migrations, allowing PostgreSQL to build the index without blocking writes or acquiring an exclusive table lock.

Backfill data in batches using Rails migration patterns to prevent long-running table locks, ensuring updates process in smaller chunks rather than a single large query on PostgreSQL.

Yes, strong_migrations aligns with safe Rails patterns by detecting dangerous operations like direct column type changes, preventing irreversible schema modifications and table locks in PostgreSQL.

Ensure Rails migration reversibility by writing both `up` and `down` methods or using reversible code blocks, applying safe patterns for schema changes, index creation, and data backfills.

Concurrent index creation is needed when adding indexes to large PostgreSQL tables in production environments to prevent table locks and avoid downtime during the migration process.