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https://issues.apache.org/jira/browse/FLINK-6969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16077552#comment-16077552
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ASF GitHub Bot commented on FLINK-6969:
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Github user sunjincheng121 commented on the issue:
https://github.com/apache/flink/pull/4183
BTW. The PR adjust the watermark by injecting a custom operator, that can
ensure the integrity of the data. It is currently reasonable, but in essence
the watermark adjustment should be carried out on the data source, that is we
should config the watermark in definition of table. In the future FLINK need to
support the DDL, we should define the watermark strategy when the define DDL.
Therefore we need a whole consideration, that is we do the first temporary
support in the PR or consider the desgin of support DDL. (just like We do the
FLINK-5921 before FLINK-5884), What do you think?
> Add support for deferred computation for group window aggregates
> ----------------------------------------------------------------
>
> Key: FLINK-6969
> URL: https://issues.apache.org/jira/browse/FLINK-6969
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Fabian Hueske
> Assignee: sunjincheng
> Attachments: screenshot-1.png
>
>
> Deferred computation is a strategy to deal with late arriving data and avoid
> updates of previous results. Instead of computing a result as soon as it is
> possible (i.e., when a corresponding watermark was received), deferred
> computation adds a configurable amount of slack time in which late data is
> accepted before the result is compute. For example, instead of computing a
> tumbling window of 1 hour at each full hour, we can add a deferred
> computation interval of 15 minute to compute the result quarter past each
> full hour.
> This approach adds latency but can reduce the number of update esp. in use
> cases where the user cannot influence the generation of watermarks. It is
> also useful if the data is emitted to a system that cannot update result
> (files or Kafka). The deferred computation interval should be configured via
> the {{QueryConfig}}.
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