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