[#MDEV-15160] Query with CTE hangs if contains straight

it should be a restriction to not use straight_join inside the anchor part of cte
testcase:

CREATE TABLE t1(a int);

INSERT INTO t1 VALUES(1),(2);

WITH RECURSIVE cte AS

	(SELECT 2 as a FROM t1 UNION ALL

	SELECT 5 FROM t1 straight_join cte)

SELECT * FROM cte;

explain WITH RECURSIVE cte AS

(SELECT 2 as a FROM t1 UNION ALL

SELECT 5 FROM t1 straight_join cte)

SELECT * FROM cte

--------------

+------+-----------------+------------+------+---------------+------+---------+------+------+------------------------------------+

| id   | select_type     | table      | type | possible_keys | key  | key_len | ref  | rows | Extra                              |

+------+-----------------+------------+------+---------------+------+---------+------+------+------------------------------------+

|    1 | PRIMARY         | <derived2> | ALL  | NULL          | NULL | NULL    | NULL |    2 |                                    |

|    2 | DERIVED         | t1         | ALL  | NULL          | NULL | NULL    | NULL |    2 |                                    |

|    3 | RECURSIVE UNION | t1         | ALL  | NULL          | NULL | NULL    | NULL |    2 |                                    |

|    3 | RECURSIVE UNION | <derived2> | ALL  | NULL          | NULL | NULL    | NULL |    2 | Using join buffer (flat, BNL join) |

| NULL | UNION RESULT    | <union2,3> | ALL  | NULL          | NULL | NULL    | NULL | NULL |                                    |

+------+-----------------+------------+------+---------------+------+---------+------+------+------------------------------------+

5 rows in set (0.001 sec)

[MDEV-15160] Query with CTE hangs if contains straight_join Created: 2018-02-01 Updated: 2018-02-15 Resolved: 2018-02-15
Status:	Closed
Project:	MariaDB Server
Component/s:	Optimizer - CTE
Affects Version/s:	10.2, 10.3
Fix Version/s:	N/A