[jira] [Commented] (FLINK-4942) Improve processing performance of HeapInternalTimerService with key groups

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-4942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15828100#comment-15828100 ] 

ASF GitHub Bot commented on FLINK-4942:
---------------------------------------

Github user StefanRRichter closed the pull request at:

    https://github.com/apache/flink/pull/2702


> Improve processing performance of HeapInternalTimerService with key groups
> --------------------------------------------------------------------------
>
>                 Key: FLINK-4942
>                 URL: https://issues.apache.org/jira/browse/FLINK-4942
>             Project: Flink
>          Issue Type: Improvement
>            Reporter: Stefan Richter
>            Assignee: Stefan Richter
>
> Currently, key groups awareness in `HeapInternalTimerService` is basically implemented as (hash) map of (hash) sets. Purpose of this is grouping key groups together in a way that allows easy serialization into key groups.
> However, this data layout comes along with some significant performance decrease, in particular when the number of key groups is high.
> I suggest to keep all timers in one set again at runtime, thus being as fast as in previous versions without key groups.
> Instead, we can perform a very fast online partitioning into key groups before a snapshot.



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