fix for #57598 (ROLLBACK should be no-op...)

[PapaToemmsn]

Change to verify proper behaviour for ROLLBACK should be no-op when no active tranaction is running (MySQL compatibility) #57598

Changelog category (leave one):

• Improvement

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Issue #57598 mentions a variant behaviour regarding transaction handling. An issued COMMIT/ROLLBACK when no transaction is active is reported as an error contrary to MySQL behaviour.

This leads to breaking the MySQL compatibility layer as some tools rely on the MySQL way to handle transactions.

Changes were tested in an environment where Clickhouse was used as a MySQL replacement.

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[PapaToemmsn]

Tried to search for information/docs on how to proceed as the results of the tests mostly seem unrelated to my changes done (e.g. "DB::Exception: io_uring is not supported by this system:" is a nerror message for quite a lot of the failed tests).

Since I was not successful in finding hints regarding these problems any hint will be greatly appreciated.

[alexey-milovidov]

The main problem is:

Bugfix validation — New test(s) failed to reproduce a bug

I've changed it to "Imrovement".

[alexey-milovidov]

PR Check — expect adding docs for pr-feature

It looks like it was also mislabeled as "New Feature"

[alexey-milovidov]

It should apply only to the MySQL compatibility. I don't think this change is correct. We can ask @tavplubix

[tavplubix]

I prefer the strict version (and for rollback as well)

[PapaToemmsn]

The issue is that this way it breaks MySQL tools as cited in #57598 so that Clickhouse can't be used as a drop in replacement for MySQL.
I share your opinion that the strict version makes sense but this denies easy usage in such scenarios.

Is there a way to get the information that the query is coming from MySQL port from the session context? If so this behaviour could be set only for such queries. Woudl that be a satisfying solution for you @tavplubix ?

[tavplubix]

Yes, it makes sense, see Context::getClientInfo() and ClientInfo::Interface

[PapaToemmsn]

@tavplubix

Yes, it makes sense, see Context::getClientInfo() and ClientInfo::Interface

Thank you for your indications. I have changed the code based on ClientInfo::Interface to show this behaviour only for MySQL interfaces. I reverted back the test and created a new one for the MySQL client to verify the new behaviour.

Is there anything else I need to do to make this pull request mergeable?

CI seems ok as the 6 tests that did not work are no related to my changes.

Thank you!