MySQL read_only 与 super_read_only 之间的关系

read_only 表示是否允许普通用户写入。如果为on，表示禁止普通用户写入。

super_read_only 表示是否禁止超级用户写入，包括普通用户，即针对所有用户。

默认关闭。

如果打开 super_read_only，则read_only会自动打开。

如果关闭 read_only，则 super_read_only 会自动关闭。

下面做下测试。

当super_read_only = 0, read_only=0，设置super_read_only=1

查看当前值：

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           0 |
+-------------------+-------------+
1 row in set (0.01 sec)

设置super_read_only=1之后，查看read_only的变化。

>set global super_read_only=1;
Query OK, 0 rows affected (0.00 sec)

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 1 |           1 |
+-------------------+-------------+
1 row in set (0.01 sec)

read_only变为1。

超级用户设置为只读后，自然普通用户也会设置只读。

当super_read_only=0, read_only=1，设置 super_read_only=1

查看当前值：

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           1 |
+-------------------+-------------+
1 row in set (0.00 sec)

设置 super_read_only=1后, 查看read_only 变化。

>set global super_read_only=1;
Query OK, 0 rows affected (0.00 sec)

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 1 |           1 |
+-------------------+-------------+
1 row in set (0.00 sec)

read_only无变化。

当super_read_only=1, read_only=0

不存在这种情况。

当super_read_only=1, read_only=1，设置super_read_only = 0

查看当前值：

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 1 |           1 |
+-------------------+-------------+
1 row in set (0.00 sec)

设置super_read_only = 0之后, 查看read_only变化。

>set global super_read_only=0;
Query OK, 0 rows affected (0.01 sec)

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           1 |
+-------------------+-------------+
1 row in set (0.00 sec)

当super_read_only = 0, read_only=0，设置read_only=1

查看当前值：

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           0 |
+-------------------+-------------+
1 row in set (0.01 sec)

设置read_only=1之后，查看super_read_only 有无变化。

>set global read_only=1;
Query OK, 0 rows affected (0.00 sec)

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           1 |
+-------------------+-------------+
1 row in set (0.00 sec)

当super_read_only = 1, read_only=0

不存在这种情况。

当super_read_only = 0, read_only=1，设置 read_only=0

查看当前值：

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           1 |
+-------------------+-------------+
1 row in set (0.00 sec)

设置 read_only=0后，查看super_read_only有无变化。

>set global read_only=0;
Query OK, 0 rows affected (0.00 sec)

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           0 |
+-------------------+-------------+
1 row in set (0.01 sec)

super_read_only变为 0。

普通用户关闭只读，超级用户的只读（也包括普通用户）也自然会关闭只读。

当super_read_only = 1, read_only=1，设置read_only=0

查看当前值：

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 1 |           1 |
+-------------------+-------------+
1 row in set (0.01 sec)

设置read_only=0之后，查看 super_read_only的变化。

>set global read_only=0;
Query OK, 0 rows affected (0.00 sec)

>select @@super_read_only, @@read_only;
+-------------------+-------------+
| @@super_read_only | @@read_only |
+-------------------+-------------+
|                 0 |           0 |
+-------------------+-------------+
1 row in set (0.01 sec)

super_read_only变为 0。

总结

关于 read_only 与 super_read_only之间的关系，实际上从其定义就可以明白。

基础很重要。