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https://issues.apache.org/jira/browse/SPARK-39893?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-39893:
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Assignee: Apache Spark
> Remove redundant aggregate if it is group only and all grouping and aggregate
> expressions are foldable
> ------------------------------------------------------------------------------------------------------
>
> Key: SPARK-39893
> URL: https://issues.apache.org/jira/browse/SPARK-39893
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.4.0
> Reporter: Wan Kun
> Assignee: Apache Spark
> Priority: Major
>
> If all groupingExpressions and aggregateExpressions in a aggregate are
> foldable, we can remove this aggregate.
> For example, query :
> {code:java}
> SELECT distinct 1001 as id , cast('2022-06-03' as date) AS DT FROM testData
> {code}
> the grouping expressions are : *[1001, 2022-06-03]*
> the aggregate expressions are : *[1001 AS id#274, 2022-06-03 AS DT#275]*
> so we can skip scan table testData and remote the aggregate operation.
> Before this PR:
> {code:java}
> Aggregate [1001, 2022-06-03], [1001 AS id#274, 2022-06-03 AS DT#275],
> Statistics(sizeInBytes=16.0 EiB)
> +- SerializeFromObject, Statistics(sizeInBytes=8.0 EiB)
> +- ExternalRDD [obj#12], Statistics(sizeInBytes=8.0 EiB)
> {code}
> After this PR:
> {code:java}
> Project [1001 AS id#218, 2022-06-03 AS DT#219], Statistics(sizeInBytes=2.0 B)
> +- OneRowRelation, Statistics(sizeInBytes=1.0 B)
> {code}
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