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From "Kostas Kloudas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4395) Eager processing of late arrivals in CEP operator
Date Tue, 28 Mar 2017 09:51:41 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15944892#comment-15944892

Kostas Kloudas commented on FLINK-4395:

Hi [~ivan.mushketyk]! How are you? 

I think this issue is not a valid one. The reason is that in CEP, the order in which elements
are processed matters. So processing elements out-of-order can lead to wrong results. You
can imagine a patter a->b->c and input (a,1) (c,2) (b,3). In this case, if c comes after
b and b is already processed then we will end up with a false match.

So I would suggest to close this JIRA and the related PR. 
What do you think?

> Eager processing of late arrivals in CEP operator
> -------------------------------------------------
>                 Key: FLINK-4395
>                 URL: https://issues.apache.org/jira/browse/FLINK-4395
>             Project: Flink
>          Issue Type: Improvement
>          Components: CEP
>            Reporter: Till Rohrmann
>            Assignee: Ivan Mushketyk
>            Priority: Minor
> At the moment elements are only processed after the CEP operator has received a watermark
larger than the elements (in EventTime mode). In case of late arrivals this means that the
late elements are not processed until the next watermark has arrived.
> In order to decrease the latency for this scenario, I propose to eagerly process late
arrivals in the CEP operator.

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