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Posted to issues@spark.apache.org by "Hyukjin Kwon (JIRA)" <ji...@apache.org> on 2019/04/11 18:42:00 UTC
[jira] [Commented] (SPARK-27440) Optimize uncorrelated predicate
subquery
[ https://issues.apache.org/jira/browse/SPARK-27440?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16815705#comment-16815705 ]
Hyukjin Kwon commented on SPARK-27440:
--------------------------------------
Please avoid to set Fix Version which is usually set when it;s actually fixed.
> Optimize uncorrelated predicate subquery
> ----------------------------------------
>
> Key: SPARK-27440
> URL: https://issues.apache.org/jira/browse/SPARK-27440
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Mingcong Han
> Priority: Major
>
> Currently, we rewrite all the predicate subqueries(InSubquery, Exists) as semi-join/anti-join. But uncorrelated predicate subquery can be evaluated using a subplan instead of a join. We can firstly rewrite all the uncorrelated predicate subqueries as `Exists`, then optimize it and compute it using a subquery physical plan like ScalarSubquery.
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