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https://issues.apache.org/jira/browse/SPARK-32542?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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karl wang resolved SPARK-32542.
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Resolution: Fixed
> Add an optimizer rule to split an Expand into multiple Expands for aggregates
> -----------------------------------------------------------------------------
>
> Key: SPARK-32542
> URL: https://issues.apache.org/jira/browse/SPARK-32542
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: karl wang
> Priority: Major
>
> Split an expand into several small Expand, which contains the Specified
> number of projections.
> For instance, like this sql.select a, b, c, d, count(1) from table1 group by
> a, b, c, d with cube. It can expand 2^4 times of original data size.
> Now we specify the spark.sql.optimizer.projections.size=4.The Expand will be
> split into 2^4/4 smallExpand.It can reduce the shuffle pressure and improve
> performance in multidimensional analysis when data is huge.
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