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/run-check_dev

Error 1064: You have an error in your SQL syntax; check the manual that corresponds to your TiDB version for the right syntax to use line 1 column 60 near ""insert into test.ts VALUES (NOW());"

I suspect there is something wrong with the parallel execution of test case:

> commands out of sync. Did you run multiple statements at once?

Which looks similiar to #30286

/hold

The change seems to be incorrect.

The sql should be written as SET GLOBAL init_connect="insert into test.ts VALUES (NOW());SET @a=1;"
This is a feature introduced in #23713, tidb will check the init_connect variable and execute the corresponding SQL for new incomming connection.

And the PR is merged in Mar 31 ... for a long I never see such fail in CI,
so I believe it might be related to the restruct of the test case #29535

There isn't much information in the error log, if it happens again I'll take a close look.

I suspect there is something wrong with the parallel execution of test case:

> commands out of sync. Did you run multiple statements at once?

Which looks similiar to #30286

Agreed. Before migrating to testify, both TestGetIndexMVCC and TestInitConnect ran serially, but now they run in parallel and this kind of error happens frequently.

Agreed. Before migrating to testify, both TestGetIndexMVCC and TestInitConnect ran serially.

Looks that we have to change them back.

@tiancaiamao Could you try to clean up all the wrongly added Parallel() functions like:

https://github.com/pingcap/tidb/pull/29535/files#diff-40acdfe302a05645257d8fc93ba27dbecaeb828d2477fd44ff9ec8d89a5c9d6bR1101

But I still have not figured out why running in parallel could cause this problem. Each Server runs separately with different ports in each tidbTestSuite and should not disturb other servers. :-(

commands out of sync. Did you run multiple statements at once? is thrown from the go-sql-driver and is not caused by running multiple statements most of the time, according to the discussion in go-sql-driver/mysql#314 .

Could it be that the error really is 'bad connection'? I.e. there were some issue when connecting, which did not get handled properly?

[2021-11-30T02:29:26.743Z]              Error:          Received unexpected error:
[2021-11-30T02:29:26.743Z]                              bad connection

I would suggest to add a db.Ping() right after the sql.Open() in runTests, to be sure the connection is working (Open does only open/create the handle, it does not actually connect yet).

There is already a PR #30306