compile_update

# File activerecord/lib/arel/crud.rb, line 17
    def compile_update(
      values,
      key = nil,
      having_clause = nil,
      group_values_columns = []
    )
      um = UpdateManager.new(source)
      um.set(values)
      um.take(limit)
      um.offset(offset)
      um.order(*orders)
      um.wheres = constraints
      um.key = key

      um.group(group_values_columns) unless group_values_columns.empty?
      um.having(having_clause) unless having_clause.nil?
      um
    end