MariaDB [test]> CREATE TABLE t0(c0 CHAR(100));

Query OK, 0 rows affected (0,030 sec)

MariaDB [test]> CREATE TABLE t1(c0 CHAR(100) UNIQUE);

Query OK, 0 rows affected (0,032 sec)

MariaDB [test]> INSERT INTO t0 VALUES ('%S'),('');

Query OK, 2 rows affected (0,003 sec)

Records: 2  Duplicates: 0  Warnings: 0

MariaDB [test]> INSERT INTO t1 VALUES (''),('*'),('\r');

Query OK, 3 rows affected (0,003 sec)

Records: 3  Duplicates: 0  Warnings: 0

MariaDB [test]> SET SESSION join_cache_level = 7;

Query OK, 0 rows affected (0,000 sec)

MariaDB [test]> SELECT t0.c0 FROM t0 NATURAL JOIN t1 WHERE TRUE RLIKE t1.c0; 

+------+

| c0   |

+------+

|      |

+------+

1 row in set (0,001 sec)

MariaDB [test]> SET STATEMENT optimizer_switch = 'join_cache_bka=off' FOR SELECT t0.c0 FROM t0 NATURAL JOIN t1 WHERE TRUE RLIKE t1.c0; 

Empty set (0,001 sec)

MariaDB [test]> SET SESSION join_cache_level = 4;

Query OK, 0 rows affected (0,000 sec)

MariaDB [test]> SELECT t0.c0 FROM t0 NATURAL JOIN t1 WHERE TRUE RLIKE t1.c0; 

Empty set (0,001 sec)

MariaDB [test]> SET STATEMENT optimizer_switch = 'join_cache_bka=off' FOR SELECT t0.c0 FROM t0 NATURAL JOIN t1 WHERE TRUE RLIKE t1.c0; 

Empty set (0,001 sec)

MariaDB [test]> SET SESSION join_cache_level = 2;

Query OK, 0 rows affected (0,000 sec)

MariaDB [test]> SELECT t0.c0 FROM t0 NATURAL JOIN t1 WHERE TRUE RLIKE t1.c0; 

+------+

| c0   |

+------+

|      |

+------+

1 row in set (0,000 sec)

MariaDB [test]> SET STATEMENT optimizer_switch = 'join_cache_bka=off' FOR SELECT t0.c0 FROM t0 NATURAL JOIN t1 WHERE TRUE RLIKE t1.c0; 

+------+

| c0   |

+------+

|      |

+------+

1 row in set (0,001 sec)