Immigrant gives Foreigner a migration generator so you can effortlessly add missing foreign keys. This is particularly helpful when you decide to add keys to an established Rails app.
Like Foreigner, Immigrant requires Rails 3.0 or greater.
Add the following to your Gemfile:
rails generate immigration AddKeys
This will create a migration named AddKeys which will have add_foreign_key statements for any missing foreign keys. Immigrant infers missing ones by evaluating the associations in your models (e.g. belongs_to, has_many, etc.). Only missing keys will be added; existing ones will never be altered or removed.
If the data in your tables is bad, then the migration will fail to run (obviously). IOW, ensure you don't have orphaned records before you try to add foreign keys.
Immigrant currently only looks for foreign keys in ActiveRecord::Base's database. So if a model is using a different database connection and it has foreign keys, Immigrant will incorrectly include them again in the generated migration.
Copyright © 2012 Jon Jensen, released under the MIT license