MariaDB [DB]> select version() ;
+---------------------+
| version()           |
+---------------------+
| 10.3.11-MariaDB-log |
+---------------------+
1 row in set (0.002 sec)

...
ENGINE=ColumnStore DEFAULT CHARSET=latin1 COMMENT 'compression=1';

MariaDB [DB]> CREATE OR REPLACE UNIQUE INDEX idx ON table(col);
ERROR 1069 (42000): Too many keys specified; max 0 keys allowed