arel_columns

# File activerecord/lib/active_record/relation/query_methods.rb, line 1051
      def arel_columns(columns)
        columns.map do |field|
          if (Symbol === field || String === field) && (klass.has_attribute?(field) || klass.attribute_alias?(field)) && !from_clause.value
            arel_attribute(field)
          elsif Symbol === field
            connection.quote_table_name(field.to_s)
          else
            field
          end
        end
      end