[jira] [Resolved] (SPARK-32241) Remove empty children of union

["Wenchen Fan (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-32241?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wenchen Fan resolved SPARK-32241.
---------------------------------
    Fix Version/s: 3.1.0
       Resolution: Fixed

Issue resolved by pull request 29053
[https://github.com/apache/spark/pull/29053]

> Remove empty children of union
> ------------------------------
>
>                 Key: SPARK-32241
>                 URL: https://issues.apache.org/jira/browse/SPARK-32241
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 3.1.0
>            Reporter: Peter Toth
>            Assignee: Peter Toth
>            Priority: Minor
>             Fix For: 3.1.0
>
>
> Empty relation children of a union can be removed.
> e.g. the plan of
> {noformat}
> SELECT c FROM t UNION ALL SELECT c FROM t WHERE FALSE{noformat}
> is currently:
> {noformat}
> == Physical Plan ==
> Union
> :- *(1) Project [value#219 AS c#222]
> :  +- *(1) LocalTableScan [value#219]
> +- LocalTableScan <empty>, [c#224]{noformat}
> but it could be improved as: 
> {noformat}
> == Physical Plan ==
> *(1) Project [value#219 AS c#222]
> +- *(1) LocalTableScan [value#219]{noformat}



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