create user 'test_user'@'localhost';
create role test_role1;
create role test_role2;

insert into mysql.roles_mapping (HostFk, UserFk, RoleFk) values ('localhost',
                                                                 'test_user',
                                                                 'test_role1');
insert into mysql.roles_mapping (HostFk, UserFk, RoleFk) values ('',
                                                                 'test_role1',
                                                                 'test_role2');
--sorted_result
select user, host from mysql.user where user not like 'root';
--sorted_result
select * from mysql.roles_mapping;

grant select on mysql.roles_mapping to test_role2@'';

flush privileges;

change_user 'test_user';

--error ER_TABLEACCESS_DENIED_ERROR
select * from mysql.roles_mapping;

--sorted_result
show grants;

select current_user(), current_role();
set role test_role1;
select current_user(), current_role();

--sorted_result
show grants;

--sorted_result
select * from mysql.roles_mapping;

--sorted_result
show grants;

use mysql;

set role none;
select current_user(), current_role();

--sorted_result
--error ER_TABLEACCESS_DENIED_ERROR
select * from mysql.roles_mapping;

change_user 'root';
drop user 'test_user'@'localhost';
select * from mysql.tables_priv;
revoke select on mysql.roles_mapping from test_role2@'';
delete from mysql.user where user like'test_%';
delete from mysql.roles_mapping where RoleFk like 'test%';

flush privileges;