Set variable tidb_skip_isolation_level_check seems not work as expected

[pcqz]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Set variable tidb_skip_isolation_level_check to on and exit

mysql> set global tidb_skip_isolation_level_check=1;
Query OK, 0 rows affected (0.09 sec)
mysql> select @@tidb_skip_isolation_level_check;
+-----------------------------------+
| @@tidb_skip_isolation_level_check |
+-----------------------------------+
|                                 1 |
+-----------------------------------+
1 row in set (0.00 sec)
mysql> exit
Bye

Login in to mysql and set unsupported isolation level

mysql> set tx_isolation='serializable';
ERROR 8048 (HY000): The isolation level 'SERIALIZABLE' is not supported. Set tidb_skip_isolation_level_check=1 to skip this error
mysql> select @@tidb_skip_isolation_level_check;
+-----------------------------------+
| @@tidb_skip_isolation_level_check |
+-----------------------------------+
|                                 1 |
+-----------------------------------+
1 row in set (0.00 sec)

mysql> set tx_isolation='serializable';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show warnings;
+---------+------+---------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                       |
+---------+------+---------------------------------------------------------------------------------------------------------------+
| Warning | 8048 | The isolation level 'SERIALIZABLE' is not supported. Set tidb_skip_isolation_level_check=1 to skip this error |
+---------+------+---------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

2. What did you expect to see? (Required)

After this variable is enabled, if setting unsupported tx_isolation, no error is reported.

3. What did you see instead (Required)

Need to query the variable first and set unsupported tx_isolation.

4. What is your TiDB version? (Required)

v5.1.0

[youngwookim]

Works on 5.0.3 version but 5.1 and 5.2 version do not work as expected. Any alternatives to avoid this bug for now?

[fzhan]

Using tidb-operator to set this variable but doesn't seems to be effective:

set global tidb_skip_isolation_level_check='on';
show VARIABLES where Variable_name = 'tidb_skip_isolation_level_check'; 

Results in

set global tidb_skip_isolation_level_check='on'
> OK
> Time: 0.05s

But
|tidb_skip_isolation_level_check | Off|

[morgo]

I believe this will be fixed in #28953

/cc @sunxiaoguang

[sunxiaoguang]

Hi @youngwookim , sorry that I wasn't able to push this fix to 5.1 and 5.2 releases during last bug triage. Will try integrating these two fixes in the coming releases.

[youngwookim]

@sunxiaoguang, No problem & thanks for your effort!

[zyguan]

So what's the progress of #28953 ? Can we close this issue if it won't be merged?

[sunxiaoguang]

So what's the progress of #28953 ? Can we close this issue if it won't be merged?

Waiting for triage for next 5.1 and 5.2 release

[zyguan]

Close the issue because #28953 & #28957 are already waiting for triage.

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.