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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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15
mysql-test/r/subselect.result
View File

@ -2835,3 +2835,18 @@ a
4 4
DROP TABLE t1,t2,t3; DROP TABLE t1,t2,t3;
purge master logs before (select adddate(current_timestamp(), interval -4 day)); 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;

14
mysql-test/t/subselect.test
View File

@ -1820,4 +1820,18 @@ DROP TABLE t1,t2,t3;
purge master logs before (select adddate(current_timestamp(), interval -4 day)); 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 # End of 4.1 tests

5
sql/sql_select.cc
View File

@ -6746,8 +6746,13 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
{ {
if (!join->first_record) if (!join->first_record)
{ {
List_iterator_fast<Item> it(*join->fields);
Item *item;
/* No matching rows for group function */ /* No matching rows for group function */
join->clear(); join->clear();
while ((item= it++))
item->no_rows_in_result();
} }
if (join->having && join->having->val_int() == 0) if (join->having && join->having->val_int() == 0)
error= -1; // Didn't satisfy having error= -1; // Didn't satisfy having