Commit d2bbf288 authored by unknown's avatar unknown
Browse files

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

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.
parent 89e41595

mysql-test/r/subselect.result

+15 −0
Original line number Diff line number Diff line
@@ -2835,3 +2835,18 @@ a 
4

DROP TABLE t1,t2,t3;

purge master logs before (select adddate(current_timestamp(), interval -4 day));

CREATE TABLE t1 (f1 INT);

CREATE TABLE t2 (f2 INT);

INSERT INTO t1 VALUES (1);

SELECT * FROM t1 WHERE f1 > ALL (SELECT f2 FROM t2);

f1

1

SELECT * FROM t1 WHERE f1 > ALL (SELECT f2 FROM t2 WHERE 1=0);

f1

1

INSERT INTO t2 VALUES (1);

INSERT INTO t2 VALUES (2);

SELECT * FROM t1 WHERE f1 > ALL (SELECT f2 FROM t2 WHERE f2=0);

f1

1

DROP TABLE t1, t2;

mysql-test/t/subselect.test

+14 −0
Original line number Diff line number Diff line
@@ -1820,4 +1820,18 @@ DROP TABLE t1,t2,t3; 


purge master logs before (select adddate(current_timestamp(), interval -4 day));





#

# Bug#18503: Queries with a quantified subquery returning empty set may

# return a wrong result. 

#

CREATE TABLE t1 (f1 INT);

CREATE TABLE t2 (f2 INT);

INSERT INTO t1 VALUES (1);

SELECT * FROM t1 WHERE f1 > ALL (SELECT f2 FROM t2);

SELECT * FROM t1 WHERE f1 > ALL (SELECT f2 FROM t2 WHERE 1=0);

INSERT INTO t2 VALUES (1);

INSERT INTO t2 VALUES (2);

SELECT * FROM t1 WHERE f1 > ALL (SELECT f2 FROM t2 WHERE f2=0);

DROP TABLE t1, t2;

# End of 4.1 tests

sql/sql_select.cc

+5 −0
Original line number Diff line number Diff line
@@ -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