Foreigner introduces a few methods to your migrations for adding and removing foreign key constraints. It also dumps foreign keys to schema.rb.
The following adapters are supported:
sqlite (foreign key methods are a no-op)
Add the following to your Gemfile:
Foreigner adds two methods to migrations.
add_foreign_key(from_table, to_table, options)
(Options are documented in connection_adapters/abstract/schema_definitions.rb):
For example, given the following model:
class Comment < ActiveRecord::Base belongs_to :post end class Post < ActiveRecord::Base has_many :comments, dependent: :delete_all end
You should add a foreign key in your migration:
The :dependent option can be moved from the has_many definition to the foreign key:
add_foreign_key(:comments, :posts, dependent: :delete)
If the column is named article_id instead of post_id, use the :column option:
add_foreign_key(:comments, :posts, column: 'article_id')
A name can be specified for the foreign key constraint:
add_foreign_key(:comments, :posts, name: 'comment_article_foreign_key')
Change Table Methods
Foreigner adds extra methods to change_table.
Add a missing foreign key to comments:
change_table :comments do |t| t.foreign_key :posts, dependent: :delete end
Remove an unwanted foreign key:
change_table :comments do |t| t.remove_foreign_key :users end
Finding Missing Foreign Keys
Use Immigrant to generate a migration that includes all missing foreign keys.
Copyright © 2012 Matthew Higgins, released under the MIT license