Bug 反馈
5.1问题，升级5.1之后发现的问题，通过设置set global tidb_skip_isolation_level_check=1;这个参数，更改后，退出登陆，后续也有重启过tidb，但仍然会出现。设置之后，使用普通账号登陆tidb，设置：SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
会报错ERROR 8048 (HY000): The isolation level ‘READ-UNCOMMITTED’ is not supported. Set tidb_skip_isolation_level_check=1 to skip this error
然而：我只要执行过：
show variables like ‘tidb_skip_isolation_level_check%’;
后续再执行：SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; 又可以了。
【 Bug 的影响】
如果客户端有设置了这个值，会一直报错无法兼容。
【可能的问题复现步骤】
[tidb@yilu-cdh-hadoop102 ~]$ mysql -uroot -p -P4000 -h127.0.0.1
Enter password:
ERROR 1045 (28000): Access denied for user ‘root’@‘127.0.0.1’ (using password: YES)
[tidb@yilu-cdh-hadoop102 ~]$ mysql -uroot -p -P4000 -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 17
Server version: 5.7.25-TiDB-v5.1.0 TiDB Server (Apache License 2.0) Community Edition, MySQL 5.7 compatible
Copyright © 2009-2020 Percona LLC and/or its affiliates
Copyright © 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.
mysql> SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
ERROR 8048 (HY000): The isolation level ‘READ-UNCOMMITTED’ is not supported. Set tidb_skip_isolation_level_check=1 to skip this error
mysql> show variables like ‘tidb_skip_isolation_level_check%’;
±--------------------------------±------+
| Variable_name | Value |
±--------------------------------±------+
| tidb_skip_isolation_level_check | ON |
±--------------------------------±------+
1 row in set (0.03 sec)
mysql> SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql>
【看到的非预期行为】
【期望看到的行为】
【相关组件及具体版本】
在5.0.1上进行测试，则正常的：
mysql -uroot -p -P4000 -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 312187
Server version: 5.7.25-TiDB-v5.0.1 TiDB Server (Apache License 2.0) Community Edition, MySQL 5.7 compatible
Copyright © 2009-2018 Percona LLC and/or its affiliates
Copyright © 2000, 2018, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.
mysql> SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
Query OK, 0 rows affected (0.01 sec)
mysql> show variables like ‘tidb_skip_isolation_level_check%’;
±--------------------------------±------+
| Variable_name | Value |
±--------------------------------±------+
| tidb_skip_isolation_level_check | ON |
±--------------------------------±------+
1 row in set (0.66 sec)
【其他背景信息或者截图】
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