ids_reader

# File activerecord/lib/active_record/associations/collection_association.rb, line 49
      def ids_reader
        if loaded?
          target.pluck(reflection.association_primary_key)
        elsif !target.empty?
          load_target.pluck(reflection.association_primary_key)
        else
          @association_ids ||= scope.pluck(reflection.association_primary_key)
        end
      end