[#MDEV-12051] Wrong results for window functions over queries with implicit grouping on always empty set.

Let 's have a table like this one:

CREATE TABLE t1 (a INT, b VARCHAR(8));

INSERT INTO t1 VALUES (1,'foo'),(2,'bar');

The following works fine:

MariaDB [test]> select max(a), row_number() over () from t1 where a > 2;

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

| max(a) | row_number() over () |

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

|   NULL |                    1 |

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

MariaDB [test]> select max(a), sum(max(a)) over () from t1 where a > 2;

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

| max(a) | sum(max(a)) over () |

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

|   NULL | NULL                |

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

MariaDB [test]> select max(a), sum(max(a)) over (partition by max(a)) from t1 where a > 2;

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

| max(a) | sum(max(a)) over (partition by max(a)) |

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

|   NULL | NULL                                   |

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

Yet these queries return wrong results:

MariaDB [test]> select max(a), row_number() over () from t1 where 1 = 2;

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

| max(a) | row_number() over () |

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

|   NULL |                    0 |

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

MariaDB [test]> select max(a), sum(max(a)) over () from t1 where 1 = 2;

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

| max(a) | sum(max(a)) over () |

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

|   NULL |                     |

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

MariaDB [test]> select max(a), sum(max(a)) over (partition by max(a)) from t1 where 1 = 2;

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

| max(a) | sum(max(a)) over (partition by max(a)) |

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

|   NULL |                                        |

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

[MDEV-12051] Wrong results for window functions over queries with implicit grouping on always empty set. Created: 2017-02-11 Updated: 2017-02-13 Resolved: 2017-02-13
Status:	Closed
Project:	MariaDB Server
Component/s:	Optimizer - Window functions
Affects Version/s:	10.2.3
Fix Version/s:	10.2.4