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https://issues.apache.org/jira/browse/SPARK-34974?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Allison Wang updated SPARK-34974:
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Parent: SPARK-35553
Issue Type: Sub-task (was: Improvement)
> Improve the subquery decorrelation framework
> --------------------------------------------
>
> Key: SPARK-34974
> URL: https://issues.apache.org/jira/browse/SPARK-34974
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.2.0
> Reporter: Allison Wang
> Assignee: Allison Wang
> Priority: Major
> Fix For: 3.2.0
>
>
> Currently, Spark has limited support for correlated subqueries. It only
> allows Filter to have outer column references and does not support
> non-equality predicates when the subquery is aggregated. Please see
> https://issues.apache.org/jira/browse/SPARK-18455 for more details on how
> subquery decorrelation works in Spark.
> The task here is to implement the technique introduced in "Unnesting
> Arbitrary Queries" by T. Neumann; A. Kemper
>
> ([http://www.btw-2015.de/res/proceedings/Hauptband/Wiss/Neumann-Unnesting_Arbitrary_Querie.pdf]).
> This allows Spark to have outer query column references other than Filter,
> decorrelate subqueries with more types of operators, and support correlated
> non-equality predicates.
> This will also enable supporting lateral derived table
> (https://issues.apache.org/jira/browse/SPARK-34382) in the future.
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