attribute_names_for_partial_inserts

# File activerecord/lib/active_record/attribute_methods/dirty.rb, line 249
        def attribute_names_for_partial_inserts
          if partial_inserts?
            changed_attribute_names_to_save
          else
            attribute_names.reject do |attr_name|
              if column_for_attribute(attr_name).default_function
                !attribute_changed?(attr_name)
              end
            end
          end
        end