10.11 patch for MDEV-37541 (Race of rolling back and committing transaction to binlog #4376
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The commit combines 1. a code polishing piece over a part of MDEV-21117 that made binlog handlerton always commit first in no 2pc cases and 2. the same rule now applies to the rollback. The 2nd point fixes the following bug. Two transactions could binlog their completions in opposite to how it is done in Engine. That is is rare situations ROLLBACK in Engine could be scheduled first by 2pc coordinator and thereby to allow for a race in binlogging of the transaction and whatever might be dependent on it in execution time. An added test demonstrates how a "child" (in execution time dependency sense) transaction could reach binlog before its parent.
The commit combines 1. a code polishing piece over a part of MDEV-21117 that made binlog handlerton always commit first in no 2pc cases and 2. the same rule now applies to the rollback. The 2nd point fixes the following bug. Two transactions could binlog their completions in opposite to how it is done in Engine. That is is rare situations ROLLBACK in Engine could be scheduled first by 2pc coordinator and thereby to allow for a race in binlogging of the transaction and whatever might be dependent on it in execution time. An added test demonstrates (requires to apply `DEBUG_SYNC(entry->thd, "before_group_commit_queue")` hunk of log.cc to the BASE) how a "child" (in execution time dependency sense) transaction can reach binlog before its parent. The rollback related code of this commit differs from the commit case in that `binlog_hton::rollback()` has to exist to satisfy its specific `ha_rollback_to_savepoint()` invoker.
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Description
This PR contains a polished version of PR-4302 comments' p.2 with the idea it to be 10.11+ patch version.
Release Notes
TODO: What should the release notes say about this change?
Include any changed system variables, status variables or behaviour. Optionally list any https://mariadb.com/kb/ pages that need changing.
How can this PR be tested?
TODO: modify the automated test suite to verify that the PR causes MariaDB to behave as intended.
Consult the documentation on "Writing good test cases".
If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.
Basing the PR against the correct MariaDB version
mainbranch.PR quality check