create user test_user@localhost;
create role test_role1;
grant test_role1 to test_user@localhost;
create role test_role2;
grant test_role2 to test_role1;
use mysql;
select * from roles_mapping;
Host	User	Role	Admin_option
	test_role1	test_role2	N
localhost	root	test_role1	Y
localhost	root	test_role2	Y
localhost	test_user	test_role1	N
rename user 'test_user'@'localhost' to 'test_user_rm'@'newhost';
select user, host from user where user like 'test%';
User	Host
test_role1	
test_role2	
test_user_rm	newhost
select * from roles_mapping;
Host	User	Role	Admin_option
	test_role1	test_role2	N
localhost	root	test_role1	Y
localhost	root	test_role2	Y
newhost	test_user_rm	test_role1	N
delete from mysql.roles_mapping;
delete from mysql.user where user like 'test%';
flush privileges;