mastodon/db/migrate/20170520145338_change_language_filter_to_opt_out.rb

class ChangeLanguageFilterToOptOut < ActiveRecord::Migration[5.0]
  def change
    remove_index :users, :allowed_languages
    remove_column :users, :allowed_languages

    add_column :users, :filtered_languages, :string, array: true, default: [], null: false
    add_index :users, :filtered_languages, using: :gin
  end
end