session optimizer_use_condition_selectivity=5 causing SQL Error (1918): Encountered illegal value '' when converting to DECIMAL

select version(),@@histogram_size, @@use_stat_tables, @@optimizer_use_condition_selectivity\G

                            version(): 10.1.12-MariaDB-1~jessie

                     @@histogram_size: 127

                    @@use_stat_tables: PREFERABLY

@@optimizer_use_condition_selectivity: 5

histogram_size=127

use_stat_tables=preferably

optimizer_use_condition_selectivity=5

in [mysqld] section.

drop table if exists a;

create table a (id int(10),cost decimal(9,2)) engine=innodb;

ANALYZE TABLE a PERSISTENT FOR ALL;

drop table if exists b;

create temporary table b (id int);

insert into b (id) select id from a where cost > 0;

Query OK, 0 rows affected, 3 warnings (0.00 sec)

Records: 0  Duplicates: 0  Warnings: 3

MariaDB [test]> show warnings;

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

| Level   | Code | Message                                                 |

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

| Warning | 1918 | Encountered illegal value '' when converting to DECIMAL |

| Warning | 1918 | Encountered illegal value '' when converting to DECIMAL |

| Warning | 1918 | Encountered illegal value '' when converting to DECIMAL |

drop table if exists a;

create table a (id int(10),cost decimal(9,2)) engine=innodb;

ANALYZE TABLE a PERSISTENT FOR ALL;

drop table if exists b;

create temporary table b (id int);

select id from a where cost > 0;

insert into b (id) select id from a where cost > 0;