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https://issues.apache.org/jira/browse/SPARK-33959?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-33959:
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Assignee: (was: Apache Spark)
> Improve the statistics estimation of the Tail
> ---------------------------------------------
>
> Key: SPARK-33959
> URL: https://issues.apache.org/jira/browse/SPARK-33959
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.2.0
> Reporter: Yuming Wang
> Priority: Major
>
> {code:scala}
> spark.sql("set spark.sql.cbo.enabled=true")
> spark.range(100).selectExpr("id as a", "id as b", "id as c", "id as
> e").write.saveAsTable("t1")
> println(Tail(Literal(5), spark.sql("SELECT * FROM
> t1").queryExecution.logical).queryExecution.explainString(org.apache.spark.sql.execution.CostMode))
> {code}
> Current:
> {noformat}
> == Optimized Logical Plan ==
> Tail 5, Statistics(sizeInBytes=3.8 KiB)
> +- Relation[a#24L,b#25L,c#26L,e#27L] parquet, Statistics(sizeInBytes=3.8 KiB)
> {noformat}
> Expected:
> {noformat}
> == Optimized Logical Plan ==
> Tail 5, Statistics(sizeInBytes=200.0 B, rowCount=5)
> +- Relation[a#24L,b#25L,c#26L,e#27L] parquet, Statistics(sizeInBytes=3.8 KiB)
> {noformat}
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