Item *Item_func::transform(THD *thd, Item_transformer transformer, uchar *argument)
{
  DBUG_ASSERT(!thd->stmt_arena->is_stmt_prepare());
  if (transform_args(thd, transformer, argument))
    return 0;
  return (this->*transformer)(thd, argument);
}
Item *Item_func::transform(THD *thd, Item_transformer transformer, uchar *argument)
{
  DBUG_ASSERT(!thd->stmt_arena->is_stmt_prepare());
  if (transform_args(thd, transformer, argument))
    return 0;
  return (this->*transformer)(thd, argument);
}