Details
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Type:
Bug
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Status: Closed
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Priority:
Major
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Resolution: Fixed
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Affects Version/s: None
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Fix Version/s: None
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Component/s: None
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Labels:
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);
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Launchpad bug id: 938131
Re: Subquery materialization is not used in CREATE TABLE SELECT
Fix released with 5.3.5-ga.