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Date: Sun, 13 Nov 2016 09:14:59 +0000 (UTC)
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Subject: [jira] [Commented] (FLINK-4937) Add incremental group window
 aggregation for streaming Table API
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archived-at: Sun, 13 Nov 2016 09:15:01 -0000


    [ https://issues.apache.org/jira/browse/FLINK-4937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15661167#comment-15661167 ] 

ASF GitHub Bot commented on FLINK-4937:
---------------------------------------

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

    https://github.com/apache/flink/pull/2792#discussion_r87708469
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/runtime/aggregate/AggregateUtil.scala ---
    @@ -61,25 +61,108 @@ object AggregateUtil {
        * }}}
        *
        */
    -  def createOperatorFunctionsForAggregates(
    +    def createOperatorFunctionsForAggregates(
    --- End diff --
    
    It is a little confused that what's the difference between these two `createOperatorFunctionsForAggregates` .  
    
    Could we remove the first one, and call `transformToAggregateFunctions` explicitly before `createOperatorFunctionsForAggregates` in DataSetAggregate ? 


> Add incremental group window aggregation for streaming Table API
> ----------------------------------------------------------------
>
>                 Key: FLINK-4937
>                 URL: https://issues.apache.org/jira/browse/FLINK-4937
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>    Affects Versions: 1.2.0
>            Reporter: Fabian Hueske
>            Assignee: sunjincheng
>
> Group-window aggregates for streaming tables are currently not done in an incremental fashion. This means that the window collects all records and performs the aggregation when the window is closed instead of eagerly updating a partial aggregate for every added record. Since records are buffered, non-incremental aggregation requires more storage space than incremental aggregation.
> The DataStream API which is used under the hood of the streaming Table API features [incremental aggregation|https://ci.apache.org/projects/flink/flink-docs-release-1.2/dev/windows.html#windowfunction-with-incremental-aggregation] using a {{ReduceFunction}}.
> We should add support for incremental aggregation in group-windows.
> This is a follow-up task of FLINK-4691.


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