columns

# File activerecord/lib/active_record/associations/join_dependency.rb, line 37
      def columns
        join_parts.collect { |join_part|
          table = join_part.aliased_table
          join_part.column_names_with_alias.collect{ |column_name, aliased_name|
            table[column_name].as Arel.sql(aliased_name)
          }
        }.flatten
      end