Subquery materialization is not used in CREATE TABLE SELECT
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
MariaDB |
Fix Released
|
High
|
Sergey Petrunia |
Bug Description
Using mariadb-5.3 create and populate table t1,t2 with the following commands:
CREATE TABLE t1(a int);
INSERT INTO t1 values(1),(2);
CREATE TABLE t2(a int);
INSERT INTO t2 values(1),(2);
Then check that the following query uses subquery materialization:
SELECT * FROM t1 WHERE a IN (SELECT * FROM t2 GROUP BY a HAVING a > 1);
MariaDB [test]> EXPLAIN SELECT * FROM t1 WHERE a IN (SELECT * FROM t2 GROUP BY a HAVING a > 1);
+----+-
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-
| 1 | PRIMARY | t1 | ALL | NULL | NULL | NULL | NULL | 2 | Using where |
| 1 | PRIMARY | <subquery2> | eq_ref | distinct_key | distinct_key | 5 | test.t1.a | 1 | |
| 2 | MATERIALIZED | t2 | ALL | NULL | NULL | NULL | NULL | 2 | Using temporary |
+----+-
In debugger check that materialization is not used for :
CREATE TABLE t3 SELECT * FROM t1 WHERE a IN (SELECT * FROM t2 GROUP BY a HAVING a > 1);
Changed in maria: | |
importance: | Undecided → High |
status: | New → Confirmed |
assignee: | nobody → Sergey Petrunia (sergefp) |
Changed in maria: | |
milestone: | none → 5.3 |
Changed in maria: | |
status: | Confirmed → Fix Committed |
Fix released with 5.3.5-ga.