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From adrian-wang <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-2213] [SQL] sort merge join for spark s...
Date Tue, 14 Apr 2015 06:04:36 GMT
Github user adrian-wang commented on a diff in the pull request:

    https://github.com/apache/spark/pull/5208#discussion_r28302364
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala
---
    @@ -41,6 +41,15 @@ case class Project(projectList: Seq[NamedExpression], child: SparkPlan)
extends
         val resuableProjection = buildProjection()
         iter.map(resuableProjection)
       }
    +
    +  /**
    +   * outputOrdering of Project is not always same with child's outputOrdering if the
certain
    +   * key is pruned, however, if the key is pruned then we must not require child using
this
    +   * ordering from upper layer, only if the ordering would not be changed by a negative,
there
    +   * would be a way to keep the ordering.
    +   * TODO: we may utilize this feature later to avoid some unnecessary sorting.
    +   */
    +  override def outputOrdering: Option[Ordering[Row]] = None
    --- End diff --
    
    We still need to consider if the projectList contains a `-`, then the ordering would be
reverted. I think we may do that carefully, probably not in this PR.


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