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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-9687) Delay the state fetch only when the triggerResult is fire
Date Mon, 09 Jul 2018 15:31:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-9687?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16537077#comment-16537077
] 

ASF GitHub Bot commented on FLINK-9687:
---------------------------------------

Github user aljoscha commented on the issue:

    https://github.com/apache/flink/pull/6224
  
    No, the motivation was different but the effect of the change is the same, I think.
    
    With this change, you can get into a situation where `Trigger.onEventTime()` returns `FIRE`
and there is actually no window contents to fire. I think this can potentially be confusing
for users that write custom triggers.
    
    I'm not saying that this behaviour is bad, I'm only saying that it changes the behaviour,
and this can be tricky. This was also the main reason why we didn't change it back when I
did the PR. If I remember correctly.
    
    What are the cases where this change leads to an improvement? I think it rarely happens
that a timer fires while a window is empty, so I think we read the window state in almost
all cases when a timer fires.


> Delay the state fetch only when the triggerResult is fire
> ---------------------------------------------------------
>
>                 Key: FLINK-9687
>                 URL: https://issues.apache.org/jira/browse/FLINK-9687
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming
>    Affects Versions: 1.5.0
>            Reporter: aitozi
>            Assignee: aitozi
>            Priority: Major
>              Labels: pull-request-available
>
> When the window operator is fired by the event timer or processing timer, it fetch the
state content first. I think it only need to fetch the content from windowState when the triggerResult
is Fire. So we have to change the order to avoid this cost ( the cost of fetch content from
state is more than judge the triggerResult). 



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