The following problem occurs with Columnstore 5.5.1 and older:

CREATE TABLE `test_utf8mb4` (
`id` varchar(36) NOT NULL,
`name` varchar(100) NOT NULL
) ENGINE=Columnstore CHARSET=utf8mb4;

CREATE TABLE `test_utf8` (
`id` varchar(36) NOT NULL,
`name` varchar(100) NOT NULL
) ENGINE=Columnstore CHARSET=utf8;

insert into test_utf8mb4 (id, name) values ('1', 'a');
insert into test_utf8mb4 (id, name) values ('2', 'b');
insert into test_utf8 (id, name) values ('1', 'a');
insert into test_utf8 (id, name) values ('2', 'b');
commit;

select count fromtest_utf8 where id in (select id from test_utf8mb4 where name in ('a')); – error: should return 1, but it returns 0
select * from test_utf8 where id in (select id from test_utf8mb4 where name in ('a')); – ok, returns 1 row !!!
select count from test_utf8mb4 where id in (select id from test_utf8 where name in ('a')); – ok, returns 1
select * from test_utf8mb4 where id in (select id from test_utf8 where name in ('a')); – ok, returns 1 row