    # File lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 646
          def references(*args)
            options = args.extract_options!
            polymorphic = options.delete(:polymorphic)
            args.each do |col|
              @base.add_column(@table_name, "#{col}_id", :integer, options)
              @base.add_column(@table_name, "#{col}_type", :string, polymorphic.is_a?(Hash) ? polymorphic : options) unless polymorphic.nil?
            end
          end