MySQL 8.0新特性之ROLE的学习笔记

Role功能可以说是一个期待已有的功能，这从它的Worklog号(WL#988)就可以看出来，这是个相当早并且呼声很高的需求了。

所谓Role，可以认为是一个权限的集合，这个集合有一个统一的名字，就是Role名，你可以为多个账户赋予统一的某个Role的权限，而权限的修改可以直接通过修改Role来实现，而无需每个账户逐一GRANT权限，大大方便了运维和管理。

Role可以被创建，修改和删除，并作用到其所属于的账户上。

举个简单的例子。创建如下测试表

mysql> create database testdb;
Query OK, 1 row affected (0.00 sec)

mysql> use testdb; create table t1 (a int, b int, primary key(a));
Database changed
Query OK, 0 rows affected (0.00 sec)

mysql> insert into t1 values (1,2);
Query OK, 1 row affected (0.00 sec)

创建Role，拥有t1表的查询权限:

mysql> create role priv_t1;
Query OK, 0 rows affected (0.00 sec)

mysql> grant select on testdb.t1 to 'priv_t1';
Query OK, 0 rows affected (0.00 sec)

创建一个账户，并将role的权限赋给它

mysql> create user 'rw_user1'@'%' identified by 'xxx';
Query OK, 0 rows affected (0.00 sec)

mysql> grant 'priv_t1' to 'rw_user1'@'%';
Query OK, 0 rows affected (0.00 sec)

以rw_user1登录

---- 查看权限

mysql> show grants;
+---------------------------------------+
| Grants for rw_user1@%        |
+---------------------------------------+
| GRANT USAGE ON *.* TO `rw_user1`@`%`  |
| GRANT `priv_t1`@`%` TO `rw_user1`@`%` |
+---------------------------------------+
2 rows in set (0.00 sec)

## 需要加using "role名"才会展开权限

mysql> show grants for 'rw_user1'@'%' using priv_t1;
+-------------------------------------------------+
| Grants for rw_user1@%                           |
+-------------------------------------------------+
| GRANT USAGE ON *.* TO `rw_user1`@`%`            |
| GRANT SELECT ON `testdb`.`t1` TO `rw_user1`@`%` |
| GRANT `priv_t1`@`%` TO `rw_user1`@`%`           |
+-------------------------------------------------+
3 rows in set (0.00 sec)

然而此时并不能直接获得t1表的查询权限， 你需要手动进行选择哪些role在账户连接上来时被激活，如下:

mysql> select * from testdb.t1;
ERROR 1142 (42000): SELECT command denied to user 'rw_user1'@'localhost' for table 't1'

mysql> SET DEFAULT ROLE ALL TO 'rw_user1'@'%';
Query OK, 0 rows affected (0.00 sec)

--- 重新登录生效

mysql> select user();
+--------------------+
| user()             |
+--------------------+
| rw_user1@localhost |
+--------------------+
1 row in set (0.00 sec)

mysql> select * from testdb.t1;
+---+------+
| a | b    |
+---+------+
| 1 |    2 |
+---+------+
1 row in set (0.00 sec)

-- SET ROLE语法参阅官方文档：
-- http://dev.mysql.com/doc/refman/8.0/en/set-default-role.html

修改role的权限，会直接作用到对应的账户上:

--- 增加insert权限
--- login as root

mysql> grant insert on testdb.t1 to 'priv_t1';
Query OK, 0 rows affected (0.00 sec)

--- login as rw_user1

mysql> insert into testdb.t1 values (2,3);
Query OK, 1 row affected (0.00 sec)

--- 删除insert权限
--- login as root

mysql> revoke insert on testdb.t1 from 'priv_t1';
Query OK, 0 rows affected (0.00 sec)

--- login as rw_user1

mysql> insert into testdb.t1 values (3,4);
ERROR 1142 (42000): INSERT command denied to user 'rw_user1'@'localhost' for table 't1'

增加了两个系统表来维护Role信息，一个是mysql.default_roles表，用于展示账户使用的默认role信息，一个是role_edges，用于展示已创建的role信息

mysql> select * from default_roles;
+------+----------+-------------------+-------------------+
| HOST | USER     | DEFAULT_ROLE_HOST | DEFAULT_ROLE_USER |
+------+----------+-------------------+-------------------+
| %    | rw_user1 | %                 | priv_t1           |
+------+----------+-------------------+-------------------+
1 row in set (0.00 sec)

mysql> select * from role_edges;
+-----------+-----------+---------+----------+-------------------+
| FROM_HOST | FROM_USER | TO_HOST | TO_USER  | WITH_ADMIN_OPTION |
+-----------+-----------+---------+----------+-------------------+
| %         | priv_t1   | %       | rw_user1 | N                 |
+-----------+-----------+---------+----------+-------------------+
1 row in set (0.00 sec)

新增函数用于显示当前账户使用的role：

mysql> select current_role();
+----------------+
| current_role() |
+----------------+
| `priv_t1`@`%`  |
+----------------+
1 row in set (0.00 sec)