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https://issues.apache.org/jira/browse/SPARK-23368?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Maryann Xue updated SPARK-23368:
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Summary: Avoid unnecessary Exchange or Sort after projection (was:
OutputOrdering and OutputPartitioning in ProjectExec should reflect the
projected columns)
> Avoid unnecessary Exchange or Sort after projection
> ---------------------------------------------------
>
> Key: SPARK-23368
> URL: https://issues.apache.org/jira/browse/SPARK-23368
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.3.0
> Reporter: Maryann Xue
> Priority: Minor
>
> After column rename projection, the ProjectExec's outputOrdering and
> outputPartitioning should reflect the projected columns as well. For example,
> {code:java}
> SELECT b1
> FROM (
> SELECT a a1, b b1
> FROM testData2
> ORDER BY a
> )
> ORDER BY a1{code}
> The inner query is ordered on a1 as well. If we had a rule to eliminate Sort
> on sorted result, together with this fix, the order-by in the outer query
> could have been optimized out.
>
> Similarly, the below query
> {code:java}
> SELECT *
> FROM (
> SELECT t1.a a1, t2.a a2, t1.b b1, t2.b b2
> FROM testData2 t1
> LEFT JOIN testData2 t2
> ON t1.a = t2.a
> )
> JOIN testData2 t3
> ON a1 = t3.a{code}
> is equivalent to
> {code:java}
> SELECT *
> FROM testData2 t1
> LEFT JOIN testData2 t2
> ON t1.a = t2.a
> JOIN testData2 t3
> ON t1.a = t3.a{code}
> , so the unnecessary sorting and hash-partitioning that have been optimized
> out for the second query should have be eliminated in the first query as well.
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