MariaDB [test]> select @@version;

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

| @@version       |

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

| 10.4.14-MariaDB |

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

1 row in set (0.000 sec)

MariaDB [test]> create table foo (a bigint(10) not null auto_increment, b int(5) not null, c bigint(10) default null, primary key (`a`));

Query OK, 0 rows affected (0.011 sec)

MariaDB [test]> insert into foo values (1,1,12);

Query OK, 1 row affected (0.003 sec)

MariaDB [test]> WITH RECURSIVE TREE AS ( SELECT a , b , c FROM foo UNION ALL SELECT A.a , A.b , A.c FROM foo AS A INNER JOIN TREE AS B ON A.c = B.a )  SELECT 0 AS b FROM dual UNION ALL SELECT b FROM TREE;

ERROR 2013 (HY000): Lost connection to MySQL server during query

MariaDB [test]> exit

[root@localhost ~]# ls -lrth /var/lib/mysql/core.63301

-rw------- 1 mysql mysql 509M Aug 28 17:48 /var/lib/mysql/core.63301

[root@localhost ~]# sudo gdb --batch --eval-command="thread apply all bt" 

/usr/sbin/mysqld /var/lib/mysql/core.63301  > mysqld_bt_all_threads.txt