MariaDB [test]> create table testtext2 (

    -> myvalue varchar(100)

    -> )engine=Columnstore CHARSET=utf8;

Query OK, 0 rows affected (1.838 sec)

MariaDB [test]> show create table testtext2;

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

| Table     | Create Table                                                                                               |

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

| testtext2 | CREATE TABLE `testtext2` (

  `myvalue` varchar(100) DEFAULT NULL

) ENGINE=Columnstore DEFAULT CHARSET=utf8 |

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

1 row in set (0.000 sec)

MariaDB [test]> alter table testtext2 change column myvalue myvalue_new varchar(100);

ERROR 1815 (HY000): Internal error: CAL0001: Alter table Failed:  Changing the datatype of a column is not supported

MariaDB [test]> alter table testtext2 change column myvalue myvalue_new varchar(300);

Query OK, 0 rows affected (0.372 sec)

Records: 0  Duplicates: 0  Warnings: 0

MariaDB [test]> show create table testtext2;

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

| Table     | Create Table                                                                                                   |

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

| testtext2 | CREATE TABLE `testtext2` (

  `myvalue_new` varchar(300) DEFAULT NULL

) ENGINE=Columnstore DEFAULT CHARSET=utf8 |

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

1 row in set (0.001 sec)