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https://issues.apache.org/jira/browse/FLINK-6969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16065056#comment-16065056
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ASF GitHub Bot commented on FLINK-6969:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/4183#discussion_r124319583
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/queryConfig.scala
---
@@ -92,6 +100,27 @@ class StreamQueryConfig private[table] extends
QueryConfig {
this
}
+ /**
+ * Specifies a deferred computation time for deferred computation,
i.e., fires the
--- End diff --
Specifies an offset for the point in time when the first result of a
time-based computation is computed. For example, a tumbling window of one hour
that ends at 13:00 would usually compute its first result at 13:00. With a
firstResultTimeOffset of 15 minutes, the first result would be computed at
13:15.
A positive firstResultTimeOffset parameter can be used to include late
arriving records into the result of an event-time based computation. Negative
offset values are not supported yet.
Later, a negative offset will allow to compute early results, i.e., an
offset of -45 minutes would compute the first and early result of the hourly
tumbling window that ends at 13:00 at 12:15.
> 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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