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https://issues.apache.org/jira/browse/SPARK-27351?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-27351:
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Assignee: peng bo (was: Apache Spark)
> Wrong outputRows estimation after AggregateEstimation with only null value
> column
> ---------------------------------------------------------------------------------
>
> Key: SPARK-27351
> URL: https://issues.apache.org/jira/browse/SPARK-27351
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.4.1
> Reporter: peng bo
> Assignee: peng bo
> Priority: Major
>
> The upper bound of group-by columns row number is to multiply distinct counts
> of group-by columns. However, column with only null value will cause the
> output row number to be 0 which is incorrect.
> Ex:
> col1 (distinct: 2, rowCount 2)
> col2 (distinct: 0, rowCount 2)
> group by col1, col2
> Actual: output rows: 0
> Expected: output rows: 2
> {code:java}
> var outputRows: BigInt = agg.groupingExpressions.foldLeft(BigInt(1))(
> (res, expr) => res *
> childStats.attributeStats(expr.asInstanceOf[Attribute]).distinctCount)
> {code}
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