MINOR:Avoid slow Set.removeAll(List) in MirrorSourceConnector

[hudeqi]

similar to #13946. The refreshTopicPartitions method is called periodically. When the number of partitions involved in replication is large, performance problems may occur.

[hudeqi]

Please help to review this minor pr, thanks! @gharris1727

[gharris1727]

Thanks for the fix @hudeqi ! I was wondering if you had plans to address this problem/warning elsewhere in the codebase?

[hudeqi]

Thanks for the fix @hudeqi ! I was wondering if you had plans to address this problem/warning elsewhere in the codebase?

I did a global search for the removeAll method of set in the codebase. There are indeed many set.removeAll(list), but this usage may have performance problems only when there are too many collection elements. At least in the connect module there is nothing extra except that mentioned in this PR.
In other modules, there may be this one that needs to be optimized to meet these conditions, which may not be suitable for mentioning in this PR (belonging to the MM2 tag). @gharris1727

[gharris1727]

LGTM. Thanks @hudeqi for addressing this in both of the Mirror connectors!

[gharris1727]

The flaky CI failures look unrelated and the mirror unit tests pass locally.