[jira] [Commented] (SPARK-4234) Always do paritial aggregation

["Venkata Ramana G (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-4234?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14198694#comment-14198694 ] 

Venkata Ramana G commented on SPARK-4234:
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As I understand currently HiveUDAF and HiveGenericUDAF support only AggregateExpression, but doesnot support partial Aggregation.
So we should support PartialAggregate for HiveUDAF and HiveGenericUDAF , using Hive UDAF's paritial aggregation interfaces.
Please correct my understanding.

> Always do paritial aggregation 
> -------------------------------
>
>                 Key: SPARK-4234
>                 URL: https://issues.apache.org/jira/browse/SPARK-4234
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Cheng Hao
>
> Currently, UDAF developer optionally implement a partial aggregation function, However this probably cause performance issue by allowing do that. We actually can always force developers to provide the partial aggregation function as Hive does, hence we will always get the `mapside` aggregation optimization.



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