Room Database Migrations: Changing Your Schema Without Losing User Data

Introduction Room Database is Android's abstraction layer over SQLite, providing compile-time checked SQL queries and reactive data flow. As your app evolves, your database schema will inevitably change: adding new columns, changing data types, removing obsolete fields. This is where migrations come in. Database migrations are one of the trickiest parts of app development. Mishandled migrations can corrupt user data, cause app crashes in production, or result in data loss. In this guide, we'll explore Room's migration system, from basic column additions to advanced schema changes, and how to test them properly. Why Database Migrations Matter When you release your app to production and users install it, their local databases are in a specific state defined by your app's schema. When you push an update with schema changes, Room needs to know how to transform the old database to the new one without losing user data. Consider this scenario: Version 1 of your app : Users table has id and na