Allison Wang created SPARK-34974:
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Summary: Improve the subquery decorrelation framework
Key: SPARK-34974
URL: https://issues.apache.org/jira/browse/SPARK-34974
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 3.2.0
Reporter: Allison Wang
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 another 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.
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