High Performance PostgreSQL for Rails

Active Record Schema Management Refresher

Active Record is used by Rails developers to evolve their database schema design. Each change is represented as a migration. The schema design is dumped (or serialized) into a file that’s committed to version control. The schema file can use a Ruby format or a SQL format. Rideshare uses the SQL format, which means the file is db/structure.sql.

If you’ve used schema management tools like Flyway^[30] or Liquibase,^[31] you’ll find similarities to Active Record migrations.

Let’s look at migration files. Migrations are versioned Ruby files in the db/migrate directory. They contain Active Record code that generates SQL Data Definition Language (DDL) statements like CREATE TABLE or CREATE INDEX. Migrations ...