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Fixed bug#18503: Queries with a quantified subquery returning empty set

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may return a wrong result.

An Item_sum_hybrid object has the was_values flag which indicates whether any
values were added to the sum function. By default it is set to true and reset
to false on any no_rows_in_result() call. This method is called only in
return_zero_rows() function. An ALL/ANY subquery can be optimized by MIN/MAX
optimization. The was_values flag is used to indicate whether the subquery
has returned at least one row. This bug occurs because return_zero_rows() is
called only when we know that the select will return zero rows before
starting any scans but often such information is not known.
In the reported case the return_zero_rows() function is not called and
the was_values flag is not reset to false and yet the subquery return no rows
Item_func_not_all and Item_func_nop_all functions return a wrong
comparison result.

The end_send_group() function now calls no_rows_in_result() for each item
in the fields_list if there is no rows were found for the (sub)query.


mysql-test/t/subselect.test:
  Added test case for bug#18503: Queries with a quantified subquery returning empty set may return a wrong result.
mysql-test/r/subselect.result:
  Added test case for bug#18503: Queries with a quantified subquery returning empty set may return a wrong result.
sql/sql_select.cc:
  Fixed bug#18503: Queries with a quantified subquery returning empty set may return a wrong result.
  
  The end_send_group() function now calls no_rows_in_result() for each item
  in the fields_list if there is no matching rows were found.
This commit is contained in:
unknown
2006-07-12 01:52:18 +04:00
parent 89e415950c
commit d2bbf288a9
3 changed files with 34 additions and 0 deletions
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5
sql/sql_select.cc
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@ -6746,8 +6746,13 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
{
if (!join->first_record)
{
List_iterator_fast<Item> it(*join->fields);
Item *item;
/* No matching rows for group function */
join->clear();
while ((item= it++))
item->no_rows_in_result();
}
if (join->having && join->having->val_int() == 0)
error= -1; // Didn't satisfy having