void Field::copy_from_tmp(int row_offset)
{
  memcpy(ptr,ptr+row_offset,pack_length());
  if (null_ptr)
  {
    *null_ptr= (uchar) ((null_ptr[0] & (uchar) ~(uint) null_bit) |
			(null_ptr[row_offset] & (uchar) null_bit));
  }
}
void Field::copy_from_tmp(int row_offset)
{
  memcpy(ptr,ptr+row_offset,pack_length());
  if (null_ptr)
  {
    *null_ptr= (uchar) ((null_ptr[0] & (uchar) ~(uint) null_bit) |
			(null_ptr[row_offset] & (uchar) null_bit));
  }
}