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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-6969) Add support for deferred computation for group window aggregates
Date Mon, 26 Jun 2017 12:00:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-6969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16062987#comment-16062987

ASF GitHub Bot commented on FLINK-6969:

Github user wuchong commented on a diff in the pull request:

    --- 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 {
    +  /**
    +    * Specifies a deferred computation time for deferred computation.
    +    */
    +  def withDeferredComputationTime(deferredComputationTime: Time): StreamQueryConfig =
    +    if (deferredComputationTime.toMilliseconds < 1) {
    --- End diff --
    I think it can be zero or one. 

> 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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