sarutak commented on a change in pull request #29677:
URL: https://github.com/apache/spark/pull/29677#discussion_r496609239
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/EnsureRequirements.scala
##########
@@ -52,7 +52,10 @@ case class EnsureRequirements(conf: SQLConf) extends
Rule[SparkPlan] {
case (child, distribution) =>
val numPartitions = distribution.requiredNumPartitions
.getOrElse(conf.numShufflePartitions)
- ShuffleExchangeExec(distribution.createPartitioning(numPartitions),
child)
+ // Like optimizer.CollapseRepartition removes adjacent repartition
operations,
+ // adjacent repartitions performed by shuffle can be also removed.
+ val newChild = if (child.isInstanceOf[ShuffleExchangeExec])
child.children.head else child
Review comment:
> it seems we need to check if outputPartitioning is the same for
narrowing down this optimization scope.
Do you mean we should check whether `outputPartitioning` of
`ShuffleExchangeExec` to be inserted and the one of the existing
`ShuffleExchangeExec`?
If you mean so, it should already match [this
condition](https://github.com/apache/spark/pull/29677/files#diff-cdb577e36041e4a27a605b6b3063fd54R48).
Just removing the existing `ShuffleExchange` and inserting the new
`ShuffleExchange` whose `outputPartitioning` satisfies the required
`Distribution` works, doesn't it?
> Btw, in my opinion, to avoid complicating the EnsureRequirements rule
more, it would be better to remove these kinds of redundant shuffles in a new
rule after EnsureRequirements like #27096.
Having a new rule sounds better.
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