LOCK TABLE T1 write; does not raise error or warning

[Alkaagr81]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

--sesson 1
drop table if exists t1,t2,t3,t11,t12;
CREATE TABLE t1 (a tinyint(3), b tinyint(5));
INSERT INTO t1 VALUES (1,1);
LOCK TABLE t1 write;

--session 2
INSERT INTO t1 VALUES (1,2); --lock wait timeout and eventually fail

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

This should return an error if not possible:

mysql> INSERT INTO t1 VALUES (1,2);   --lock wait timeout and eventually fail

3. What did you see instead (Required)

--session 1
drop table if exists t1,t2,t3,t11,t12;
CREATE TABLE t1 (a tinyint(3), b tinyint(5));
INSERT INTO t1 VALUES (1,1);
LOCK TABLE t1 write;

--session 2
INSERT INTO t1 VALUES (1,2); --session 2 is still allow to insert data in t1

4. What is your TiDB version? (Required)

 Release Version: v5.2.1                                          +
 Edition: Community                                               +
 Git Commit Hash: cd8fb24c5f7ebd9d479ed228bb41848bd5e97445        +
 Git Branch: heads/refs/tags/v5.2.1                               +
 UTC Build Time: 2021-09-08 02:29:53                              +
 GoVersion: go1.16.4                                              +
 Race Enabled: false                                              +
 TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306+
 Check Table Before Drop: false 
(1 row)

[morgo]

I took a look into this today. It might be that TiDB needs to permit this syntax to work with restores from mysqldump, but it should be possible to at least return a warning when tidb_enable_noop_funcs is set toOFF. Otherwise users might be led to believe that the table is being locked, and this could lead to data corruption cases.

[Defined2014]

/assign

[Defined2014]

The lock/unlock table feature is implemented by #10343 which is controled by enable-table-lock in config file.
After discussed with @crazycs520 , he didn't suggest us default enable this function because it will cause performance degradation.
Maybe we could add warning information when enable-table-lock equals false. What do you think of it? @morgo

[morgo]

The lock/unlock table feature is implemented by #10343 which is controled by enable-table-lock in config file. After discussed with @crazycs520 , he didn't suggest us default enable this function because it will cause performance degradation. Maybe we could add warning information when enable-table-lock equals false. What do you think of it? @morgo

Yes, a warning is much better than noop.

[jebter]

Do we need to adjust the severity to moderate？ @morgo @Defined2014

[morgo]

Do we need to adjust the severity to moderate？ @morgo @Defined2014

By triage definition it is critical: TiDB is implying that it is locking tables while giving no feedback to users. This has a high chance of leading to data corruption.

[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.