  void prepare_interval_field_calc_length()
  {
    uint32 field_length, dummy;
    if (real_field_type() == MYSQL_TYPE_SET)
    {
      calculate_interval_lengths(&dummy, &field_length);
      length= field_length + (interval->count - 1);
    }
    else /* MYSQL_TYPE_ENUM */
    {
      calculate_interval_lengths(&field_length, &dummy);
      length= field_length;
    }
    set_if_smaller(length, MAX_FIELD_WIDTH - 1);
  }
  void prepare_interval_field_calc_length()
  {
    uint32 field_length, dummy;
    if (real_field_type() == MYSQL_TYPE_SET)
    {
      calculate_interval_lengths(&dummy, &field_length);
      length= field_length + (interval->count - 1);
    }
    else  
    {
      calculate_interval_lengths(&field_length, &dummy);
      length= field_length;
    }
    set_if_smaller(length, MAX_FIELD_WIDTH - 1);
  }