Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/17331#discussion_r106797457
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/SortMergeJoinExec.scala
---
@@ -80,7 +80,18 @@ case class SortMergeJoinExec(
override def requiredChildDistribution: Seq[Distribution] =
ClusteredDistribution(leftKeys) :: ClusteredDistribution(rightKeys) ::
Nil
- override def outputOrdering: Seq[SortOrder] = requiredOrders(leftKeys)
+ override def outputOrdering: Seq[SortOrder] = joinType match {
+ case RightOuter =>
+ // For right outer join, values of the left key will be filled with
nulls if it can't
+ // match the value of the right key, so `nullOrdering` of the left
key can't be guaranteed.
+ // We should output right key order here.
--- End diff --
This comment is misleading. The output ordering is mainly affected by how
we implement SortMergeJoinExec.
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