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https://issues.apache.org/jira/browse/FLINK-7347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16131967#comment-16131967
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ASF GitHub Bot commented on FLINK-7347:
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Github user aljoscha commented on the issue:
https://github.com/apache/flink/pull/4468
Thanks a lot for contributing this fix, @ymost! 👍
I merged into master, could you please close this PR?
> "removeAll" is extremely inefficient in
> MessageAcknowledgingSourceBase.notifyCheckpointComplete
> -----------------------------------------------------------------------------------------------
>
> Key: FLINK-7347
> URL: https://issues.apache.org/jira/browse/FLINK-7347
> Project: Flink
> Issue Type: Improvement
> Components: DataStream API
> Affects Versions: 1.3.1
> Reporter: Yonatan Most
> Assignee: Yonatan Most
> Fix For: 1.4.0
>
>
> Observe this line in
> {{MessageAcknowledgingSourceBase.notifyCheckpointComplete}}:
> {code}
> idsProcessedButNotAcknowledged.removeAll(checkpoint.f1);
> {code}
> The implementation of {{removeAll}} is such that if the set is smaller than
> the collection to remove, then the set is iterated and every item is checked
> for containment in the collection. The type of {{checkpoint.f1}} here is
> {{ArrayList}}, so the {{contains}} action is very inefficient, and it is
> performed for every item in {{idsProcessedButNotAcknowledged}}.
> In our pipeline we had about 10 million events processed, and the checkpoint
> was stuck on the {{removeAll}} call for hours.
> A simple solution is to make {{idsForCurrentCheckpoint}} a {{HashSet}}
> instead of an {{ArrayList}}. The fact that it's a list is not really used
> anywhere.
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