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