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https://issues.apache.org/jira/browse/FLINK-6969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16062988#comment-16062988
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ASF GitHub Bot commented on FLINK-6969:
---------------------------------------
Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/4183#discussion_r123990133
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/queryConfig.scala
---
@@ -92,6 +100,23 @@ class StreamQueryConfig private[table] extends
QueryConfig {
this
}
+ /**
+ * Specifies a deferred computation time for deferred computation.
--- End diff --
We should enrich this comment. What is it used for? What is the impact of
this setting?
> 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
>
> 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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