double Item_sum_avg::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (aggr)
    aggr->endup();
  if (!count)
  {
    null_value=1;
    return 0.0;
  }
  return Item_sum_sum::val_real() / ulonglong2double(count);
}
double Item_sum_avg::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (aggr)
    aggr->endup();
  if (!count)
  {
    null_value=1;
    return 0.0;
  }
  return Item_sum_sum::val_real() / ulonglong2double(count);
}