Immigrant gives Rails a foreign key migration generator so you can effortlessly find and add missing keys. This is particularly helpful when you decide to add keys to an established Rails app.
Add the following to your Gemfile:
If you're using a version of Rails prior to 4.2, you'll also need the Foreigner gem.
rails generate immigration AddKeys
This will create a migration named AddKeys which will have
statements for any missing foreign keys. Immigrant infers missing ones by
evaluating the associations in your models (e.g.
Only missing keys will be added; existing ones will never be altered or
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
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
Copyright (c) 2012-2014 Jon Jensen, released under the MIT license