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https://issues.apache.org/jira/browse/FLINK-6242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15973419#comment-15973419
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ASF GitHub Bot commented on FLINK-6242:
---------------------------------------

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

    https://github.com/apache/flink/pull/3735#discussion_r111994200
  
    --- Diff: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/aggregate/DataSetPreAggFunction.scala
 ---
    @@ -64,38 +68,22 @@ class DataSetPreAggFunction(
       def preaggregate(records: Iterable[Row], out: Collector[Row]): Unit = {
    --- End diff --
    
    I think we can move the implementation of `preaggregate()` to `combine()` 
and let `mapPartition()` call `combine()`. `combine()` is called for groups for 
records with the key and `mapPartition()` just once (for the whole partition). 
This way we can remove some overhead from `combine()`.


> codeGen DataSet Goupingwindow Aggregates
> ----------------------------------------
>
>                 Key: FLINK-6242
>                 URL: https://issues.apache.org/jira/browse/FLINK-6242
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>            Reporter: Shaoxuan Wang
>            Assignee: Shaoxuan Wang
>




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