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https://issues.apache.org/jira/browse/FLINK-7471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16132090#comment-16132090
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sunjincheng commented on FLINK-7471:
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We know it's poor compute if all aggregates for each record completely from
scratch performance. that's why we using {{retract}} method to implement
BOUNDED OVER WINDOW. I think that's the best choice.
We also have add the comment in {{AggregateFunction}} for {{retract}} method.
{code}
...
This(retract) function must be implemented for
datastream bounded over aggregate.
{code}
So, I think we did the right thing when we do the aggregate design and
implementation of the bounded over.
But I think using the {{retract}} method is an optimized implementation of
bounded over window, but we can not force the user to implement the {{retract}}
method. especially the business scenario is an append only table that never
generates retract information, so the user may define a aggregate function that
does not have a retract method. we can not force the user must implement the
retract method because of the way of realization for bounded over window. And I
think we may not need a lot of refactoring the original code, but on the basis
of the original code to increase the non-retract method support.
[~fhueske] I think your worry is necessary, but I do not really like the
implementation of the OVER window will force the user to implement the
AggregateFunction # retract method.
> Improve bounded OVER support non-retract method AGG
> ---------------------------------------------------
>
> Key: FLINK-7471
> URL: https://issues.apache.org/jira/browse/FLINK-7471
> Project: Flink
> Issue Type: Improvement
> Components: Table API & SQL
> Reporter: sunjincheng
> Assignee: sunjincheng
>
> Currently BOUNDED OVER WINDOW only support have {{retract}} method AGG. In
> this JIRA. will add non-retract method support.
> What do you think? [~fhueske]
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