class AddEnumerationsPosition < ActiveRecord::Migration[4.2] def self.up add_column(:enumerations, :position, :integer, :default => 1) unless Enumeration.column_names.include?('position') Enumeration.all.group_by(&:opt).each do |opt, enums| enums.each_with_index do |enum, i| # do not call model callbacks Enumeration.where({:id => enum.id}).update_all(:position => (i+1)) end end end def self.down remove_column :enumerations, :position end end