Columnstore executes join on incompatible types

create table join1  (x varchar(2), y varchar(10)) engine=columnstore;

create table join2  (x varchar(2), y date, z int) engine=columnstore;

insert into join1 values("11", "2017-01-01");

insert into join1 values("12", "2017-01-02");

insert into join2 values("11", "2017-01-01", 22);

insert into join2 values("12", "2017-02-01", 23);

select a.*, b.*

from join1 a

left join join2 b

on a.x = b.x and a.y = b.y

x	y	x	y	z

11	2017-01-01	11	2017-01-01	22

select a.*, b.*

from join1 a

left join join2 b

on a.y = b.y