[jira] [Updated] (SPARK-24254) Eagerly evaluate some subqueries over LocalRelation

["Dongjoon Hyun (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-24254?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dongjoon Hyun updated SPARK-24254:
----------------------------------
    Affects Version/s:     (was: 2.4.0)
                       3.0.0

> Eagerly evaluate some subqueries over LocalRelation
> ---------------------------------------------------
>
>                 Key: SPARK-24254
>                 URL: https://issues.apache.org/jira/browse/SPARK-24254
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 3.0.0
>            Reporter: Henry Robinson
>            Priority: Major
>
> Some queries would benefit from evaluating subqueries over {{LocalRelations}} eagerly. For example:
> {code}
> SELECT t1.part_col FROM t1 JOIN (SELECT max(part_col) m FROM t2) foo WHERE t1.part_col = foo.m
> {code}
> If {{max(part_col)}} could be evaluated during planning, there's an opportunity to prune all but at most one partitions from the scan of {{t1}}. 
> Similarly, a near-identical query with a non-scalar subquery in the {{WHERE}} clause:
> {code}
> SELECT * FROM t1 WHERE part_col IN (SELECT part_col FROM t2)
> {code}
> could be partially evaluated to eliminate some partitions, and remove the join from the plan. 
> Obviously all subqueries over local relations can't be evaluated during planning, but certain whitelisted aggregates could be if the input cardinality isn't too high. 



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