MariaDB [test]>  drop table if exists t2;

Query OK, 0 rows affected (0.335 sec)

MariaDB [test]> create table t2 (a int) engine=Columnstore comment 'compression=0';

Query OK, 0 rows affected (0.463 sec)

MariaDB [test]> insert into t2 select 1 from seq_1_to_300000;

Query OK, 300000 rows affected (1.213 sec)

Records: 300000  Duplicates: 0  Warnings: 0

MariaDB [test]> alter table t2 add b int;

Query OK, 0 rows affected (0.512 sec)              

Records: 0  Duplicates: 0  Warnings: 0

MariaDB [test]> insert into t2 select 2, 3 from seq_1_to_300000;

Query OK, 300000 rows affected (1.217 sec)

Records: 300000  Duplicates: 0  Warnings: 0