group

# File activerecord/lib/arel/update_manager.rb, line 32
    def group(columns)
      columns.each do |column|
        column = Nodes::SqlLiteral.new(column) if String === column
        column = Nodes::SqlLiteral.new(column.to_s) if Symbol === column

        @ast.groups.push Nodes::Group.new column
      end

      self
    end