support non equality based joins and correlated subqueries

CREATE TABLE `test1` (
`c1` int(10) unsigned DEFAULT NULL,
`c2` char(16) DEFAULT NULL
) ENGINE=Columnstore DEFAULT CHARSET=utf8;

INSERT INTO `test1` VALUES ('1', 'test1');
INSERT INTO `test1` VALUES ('2', 'test2');

CREATE TABLE `test2` (
`c1` int(10) unsigned DEFAULT NULL,
`c2` char(16) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

INSERT INTO `test2` VALUES ('1', 'test1');

MariaDB [test]> select * from test1;
-----------+

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

-----------+
2 rows in set (0.11 sec)

MariaDB [test]> select * from test2;
-----------+

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

-----------+
1 row in set (0.00 sec)

select * from test1 t1 where not exists (select c1 from test2 t2 where t1.c1>t2.c1);

ERROR 1815 (HY000): Internal error: IDB-1000: 't1' and 'sub-query' are not joined.