schema_ferry

https://github.com/kyuuri1791/schema_ferry

schema_ferry keeps a PostgreSQL schema in sync with a MySQL source during a gradual migration. It reads the MySQL schema through ActiveRecord, converts it to PostgreSQL equivalents — with a declarative DSL for type mappings, enum handling, and per-table overrides — and applies only the diff, idempotently, via ridgepole. Ships a Ruby API and a cron-friendly CLI.