#create a user with no privileges
create user 'test_user'@'localhost';
create role test_role1;
create role test_role2;

grant test_role1 to test_user@localhost;
grant test_role2 to test_user@localhost;
grant test_role2 to test_role1;
--sorted_result
select user, host from mysql.user where user not like 'root';
--sorted_result
select * from mysql.roles_mapping;

--sorted_result
select user, host from mysql.db;

grant select on mysql.* to test_role2;
flush privileges;

change_user 'test_user';

--error ER_TABLEACCESS_DENIED_ERROR
select * from mysql.roles_mapping;

select current_user(), current_role();
set role test_role1;
select current_user(), current_role();
--sorted_result
select * from mysql.roles_mapping;
set role none;
select current_user(), current_role();
--error ER_TABLEACCESS_DENIED_ERROR
select * from mysql.roles_mapping;
set role test_role2;
select current_user(), current_role();
--sorted_result
select * from mysql.roles_mapping;

change_user 'root';
drop user 'test_user'@'localhost';
revoke select on mysql.* from test_role2;
delete from mysql.user where user='test_role1';
delete from mysql.user where user='test_role2';
delete from mysql.roles_mapping where Role='test_role1';
delete from mysql.roles_mapping where Role='test_role2';
flush privileges;