```ruby
class CreateFriendships < ActiveRecord::Migration
  def change
    create_table :friendships do |t|
      t.references :user, index: true, foreign_key: true
      t.references :friend, class: 'User', index: true, foreign_key: true

      t.timestamps null: false
    end
  end
end
```

Change friendships migration for Heroku pg.
user
```ruby
class CreateFriendships < ActiveRecord::Migration
  def change
    create_table :friendships do |t|
      t.references :user, index: true, foreign_key: true
      t.integer :friend_id, class: 'User', index: true, foreign_key: true

      t.timestamps null: false
    end
  end
end
```
assistant