Wrong result with RIGHT/LEFT JOIN and ALL subquery predicate in WHERE condition
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
MariaDB |
Fix Released
|
High
|
Oleksandr "Sanja" Byelkin |
Bug Description
The following sequence of commands gives us a wrong result set in mariadb-5.2:
CREATE TABLE t1(a INT);
INSERT INTO t1 VALUES(9);
CREATE TABLE t2(b INT);
INSERT INTO t2 VALUES(8);
CREATE TABLE t3(c INT);
INSERT INTO t3 VALUES(3);
SELECT * FROM t2 RIGHT JOIN t3 ON(c = b) WHERE b < ALL(SELECT a FROM t1 WHERE a <= 7);
MariaDB [test]> SELECT * FROM t2 RIGHT JOIN t3 ON(c = b) WHERE b < ALL(SELECT a FROM t1 WHERE a <= 7);
Empty set (0.00 sec)
MariaDB [test]> EXPLAIN EXTENDED SELECT * FROM t2 RIGHT JOIN t3 ON(c = b) WHERE b < ALL(SELECT a FROM t1 WHERE a <= 7);
+----+-
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-
| 1 | PRIMARY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE noticed after reading const tables |
| 2 | SUBQUERY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE noticed after reading const tables |
+----+-
2 rows in set, 1 warning (0.00 sec)
MariaDB [test]> show warnings;
+------
| Level | Code | Message |
+------
| Note | 1003 | select '8' AS `b`,'3' AS `c` from `test`.`t3` join `test`.`t2` where 0 |
+------
The bug is not reproducible in mariadb-5.3:
MariaDB [test]> select version();
+------
| version() |
+------
| 5.3.6-MariaDB-debug |
+------
MariaDB [test]> SELECT * FROM t2 RIGHT JOIN t3 ON(c = b) WHERE b < ALL(SELECT a FROM t1 WHERE a <= 7);
+------+------+
| b | c |
+------+------+
| NULL | 3 |
+------+------+
MariaDB [test]> EXPLAIN EXTENDED SELECT * FROM t2 RIGHT JOIN t3 ON(c = b) WHERE b < ALL(SELECT a FROM t1 WHERE a <= 7);
+----+-
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-
| 1 | PRIMARY | t3 | system | NULL | NULL | NULL | NULL | 1 | 100.00 | |
| 1 | PRIMARY | t2 | system | NULL | NULL | NULL | NULL | 1 | 100.00 | |
| 2 | SUBQUERY | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE noticed after reading const tables |
+----+-
MariaDB [test]> show warnings;
+------
| Level | Code | Message |
+------
| Note | 1003 | select NULL AS `b`,3 AS `c` from `test`.`t3` left join `test`.`t2` on(0) where <not>(<
+------
(See also bug #13735712 for mysql code line)
Changed in maria: | |
status: | New → Confirmed |
importance: | Undecided → High |
assignee: | nobody → Oleksandr "Sanja" Byelkin (sanja-byelkin) |
milestone: | none → 5.2 |
Changed in maria: | |
status: | Confirmed → In Progress |
Changed in maria: | |
status: | In Progress → Fix Committed |
tags: | added: optimizer wrong-result |
Changed in maria: | |
status: | Fix Committed → Fix Released |
The subquery was never optimized (so and executed).