maria-developers team mailing list archive

[Sergei Petrunia <psergey@xxxxxxxxxxxx>]

On Mon, May 14, 2012 at 04:35:10PM +0400, Sergei Petrunia wrote:
> > 
> A general question: was this expected to work:
> 
> MariaDB [j3]> explain extended select * from t1 where 33 in (select b from
> five) or c > 11;
> +------+--------------------+-------+------+---------------+------+---------+------+------+----------+-------------+
> | id   | select_type        | table | type | possible_keys | key  | key_len |
> ref  | rows | filtered | Extra       |
> +------+--------------------+-------+------+---------------+------+---------+------+------+----------+-------------+
> |    1 | PRIMARY            | t1    | ALL  | NULL          | NULL | NULL    |
> NULL |   10 |   100.00 | Using where |
> |    2 | DEPENDENT SUBQUERY | five  | ALL  | NULL          | NULL | NULL    |
> NULL |    5 |   100.00 | Using where |
> +------+--------------------+-------+------+---------------+------+---------+------+------+----------+-------------+
> 2 rows in set, 1 warning (22 min 25.44 sec)
> 
> The subuqery is constant, table `five` has 5 records, and none of them has
> b=33.  When debugging, I see JOIN::get_examined_rows() to be invoked and it
> returns 5 rows,  but EXPLAIN still doesn't show "Impossible WHERE"? 

Full example:

create table ten (a int);
insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (a int, b int, c int);
insert into t1 select a,a,a from ten;
create table five (a int, b int, c int);
insert into five select a,a,a from ten limit 5;

BR
 Sergei
-- 
Sergei Petrunia, Software Developer
Monty Program AB, http://askmonty.org
Blog: http://s.petrunia.net/blog