```ruby
class AddStateToSignups < ActiveRecord::Migration[5.0]
  def change
    add_column :signups, :state, :string, null: false, index: true
  end
end
```

Add default value to not-null column (not having one is illegal in SQLite)
user
```ruby
class AddStateToSignups < ActiveRecord::Migration[5.0]
  def change
    add_column :signups, :state, :string, null: false, default: 'confirmed', index: true
  end
end
```
assistant