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https://issues.apache.org/jira/browse/SPARK-39429?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-39429:
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Assignee: (was: Apache Spark)
> Convert Inner Join With Aggregate To Semi Join
> ----------------------------------------------
>
> Key: SPARK-39429
> URL: https://issues.apache.org/jira/browse/SPARK-39429
> Project: Spark
> Issue Type: Improvement
> Components: Optimizer
> Affects Versions: 3.2.1
> Reporter: Li Xian
> Priority: Minor
>
> Inner Join with aggregation on one of its child it equivalent to a Semi Join
> with the aggregation eliminated If the aggregation is just doing grouping and
> all the grouping columns appears in the join condition.
> For example, Inner Join like below
>
> {code:java}
> select * from table1 inner join (select key2 from table2 group by key2)
> subquery on table1.key1 = subquery.key2{code}
> can be transformed to a semi join and eliminate the aggregate in the subquery
>
>
> {code:java}
> select * from table1 semi join (select key2 from table2) subquery on
> table1.key1 = subquery.key2
> {code}
>
> I think this can be added as a optimize rule to save the unnecessary
> aggregation in the subquery.
>
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