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From "Xingcan Cui (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7245) Enhance the operators to support holding back watermarks
Date Tue, 25 Jul 2017 00:12:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16099299#comment-16099299
] 

Xingcan Cui commented on FLINK-7245:
------------------------------------

Sure. I'll draw up a design document for that, as well as for dynamic timestamp acquisition.

> Enhance the operators to support holding back watermarks
> --------------------------------------------------------
>
>                 Key: FLINK-7245
>                 URL: https://issues.apache.org/jira/browse/FLINK-7245
>             Project: Flink
>          Issue Type: New Feature
>          Components: DataStream API
>            Reporter: Xingcan Cui
>            Assignee: Xingcan Cui
>
> Currently the watermarks are applied and emitted by the {{AbstractStreamOperator}} instantly.

> {code:java}
> public void processWatermark(Watermark mark) throws Exception {
> 	if (timeServiceManager != null) {
> 		timeServiceManager.advanceWatermark(mark);
> 	}
> 	output.emitWatermark(mark);
> }
> {code}
> Some calculation results (with timestamp fields) triggered by these watermarks (e.g.,
join or aggregate results) may be regarded as delayed by the downstream operators since their
timestamps must be less than or equal to the corresponding triggers. 
> This issue aims to add another "working mode", which supports holding back watermarks,
to current operators. These watermarks should be blocked and stored by the operators until
all the corresponding new generated results are emitted.



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