SQL Adapter » Migrations

The SQL adapter uses Sequel migration API exposed by SQL gateways. You can either use the built-in rake tasks, or handle migrations manually.

Migration Rake Tasks

To load migration tasks simply require them and provide db:setup task which sets up ROM.

# your rakefile

require 'rom/sql/rake_task'

namespace :db do
  task :setup do
    # your ROM setup code
    # Usually something like this:
    # ROM::SQL::RakeSupport.env = ROM.container(...)
  end
end

The following tasks are available:

  • rake db:create_migration[create_users] - create migration file under db/migrate
  • rake db:migrate - runs migrations located in db/migrate
  • rake db:clean - removes all tables
  • rake db:reset - removes all tables and re-runs migrations

File-based migrations

Migrations created with a command such as rake db:create_migration[create_users] will be placed at under the db/migrate folder at the root of your project.

These migrations should follow this syntax:

ROM::SQL.migration do
  change do
    create_table :users do
      primary_key :id
      column :name, String, null: false
    end
  end
end

Filenames for migrations begin with the datestamp following this convention date +%Y%m%d%H%M%S. That is: 4 digits for the year, followed by 2 digits for the month, day, hour, minute and second the migration was created. This provides an order to the migrations so you can migrate and build your database up piece-by-piece in the same order every time.

Using Gateway Migration Interface

You can also use migrations by using a gateway's interface:

rom = ROM.container(:sql, 'postgres://localhost/rom')

gateway = rom.gateways[:default]

migration = gateway.migration do
  change do
    create_table :users do
      primary_key :id
      column :name, String, null: false
    end
  end
end

migration.apply(gateway.connection, :up)

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