A gem to use Rails Database Migrations in non Rails projects


Rails migrations in non-Rails (and non Ruby) projects.


In the 4.x release we have moved to using Rails 4 migrations instead of maintaining our own migration related code. Just about anything you can do with Rails 4 migrations you can now do with Standalone Migrations too!


Standalone Migrations relies on the contributions of the open-source community! To submit a fix or an enhancement fork the repository, checkout the develop branch, make your changes, add your name to the Contributors section in README.markdown, and send us a pull request! If you're active and do good work we'll add you as a collaborator!


Install Ruby, RubyGems and a ruby-database driver (e.g. gem install mysql) then:

$ gem install standalone_migrations

Add to Rakefile in your projects base directory:

require 'standalone_migrations'

Add database configuration to db/config.yml in your projects base directory e.g.:

  adapter: sqlite3
  database: db/development.sqlite3
  pool: 5
  timeout: 5000

  adapter: mysql
  encoding: utf8
  reconnect: false
  database: somedatabase_dev
  pool: 5
  username: root
  socket: /var/run/mysqld/mysqld.sock

test: &test
  adapter: sqlite3
  database: db/test.sqlite3
  pool: 5
  timeout: 5000

To create a new database migration:

rake db:new_migration name=foo_bar_migration
edit db/migrate/20081220234130_foo_bar_migration.rb

If you really want to, you can just execute raw SQL:

def up
  execute "insert into foo values (123,'something');"

def down
  execute "delete from foo where field='something';"

To apply your newest migration:

rake db:migrate

To migrate to a specific version (for example to rollback)

rake db:migrate VERSION=20081220234130

To migrate a specific database (for example your "testing" database)

rake db:migrate RAILS_ENV=test

To execute a specific up/down of one single migration

rake db:migrate:up VERSION=20081220234130

To revert your last migration

rake db:rollback

To revert your last 3 migrations

rake db:rollback STEP=3

Custom configuration

By default, Standalone Migrations will assume there exists a "db/" directory in your project. But if for some reason you need a specific directory structure to work with, you can use a configuration file named .standalone_migrations in the root of your project containing the following:

    seeds: db/seeds.rb
    migrate: db/migrate
    schema: db/schema.rb
    database: db/config.yml

These are the configurable options available. You can omit any of the keys and Standalone Migrations will assume the default values.

on_loaded callbacks

If you would like to use an external library such as foreigner with standalone migrations, you can add the following to your Rakefile:

require 'foreigner'

StandaloneMigrations.on_loaded do

Multiple database support


Create a custom configuration file for each database and name them .database_name.standalone_migrations. The same conditions apply as described under Custom Configuration, however you are most likely want to specify all options to avoid conflicts and errors.

An example set up would look like this:

|-- db/
|   |-- migrate/
|   |   |-- db1/
|   |   |   |-- 001_migration.rb
|   |   |   
|   |   |-- db2/
|   |       |-- 001_migration.rb
|   |    
|   |-- config_db1.yml
|   |-- config_db2.yml
|   |-- seeds_db1.rb
|   |-- seeds_db2.rb
|   |-- schema_db1.rb
|   |-- schema_db2.rb
|-- .db1.standalone_migrations
|-- .db2.standalone_migrations

Sample config file:

    seeds: db/seeds_db1.rb
    migrate: db/migrate/db1
    schema: db/schema_db1.rb
    database: db/config_db1.yml

Of course you can achieve a different layout by simply editing the paths.


You can run the Rake tasks on a particular database by passing the DATABASE environment variable to it:

$ rake db:version DATABASE=db1

Combined with the environment selector:

$ rake db:migrate DATABASE=db2 RAILS_ENV=production

Changing environment config in runtime

If you are using Heroku or have to create or change your connection configuration based on runtime aspects (maybe environment variables), you can use the StandaloneMigrations::Configurator.environments_config method. Check the usage example:

require 'tasks/standalone_migrations'

StandaloneMigrations::Configurator.environments_config do |env|

  env.on "production" do

    if (ENV['DATABASE_URL'])
      db = URI.parse(ENV['DATABASE_URL'])
      return {
        :adapter  => db.scheme == 'postgres' ? 'postgresql' : db.scheme,
        :host     => db.host,
        :username => db.user,
        :password => db.password,
        :database => db.path[1..-1],
        :encoding => 'utf8'



You have to put this anywhere on your Rakefile. If you want to change some configuration, call the #on method on the object received as argument in your block passed to ::environments_config method call. The #on method receives the key to the configuration that you want to change within the block. The block should return your new configuration hash or nil if you want the configuration to stay the same.

Your logic to decide the new configuration need to access some data in your current configuration? Then you should receive the configuration in your block, like this:

require 'tasks/standalone_migrations'

StandaloneMigrations::Configurator.environments_config do |env|

  env.on "my_custom_config" do |current_custom_config|
    p current_custom_config
    # => the values on your current "my_custom_config" environment


Exporting Generated SQL

If instead of the database-agnostic schema.rb file you'd like to save the database-specific SQL generated by the migrations, simply add this to your Rakefile.

require 'tasks/standalone_migrations'
ActiveRecord::Base.schema_format = :sql

You should see a db/structure.sql file the next time you run a migration.