cloud-fan commented on a change in pull request #29307:
URL: https://github.com/apache/spark/pull/29307#discussion_r463384641
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/ShuffleExchangeExec.scala
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@@ -83,7 +83,12 @@ trait ShuffleExchangeLike extends Exchange {
case class ShuffleExchangeExec(
override val outputPartitioning: Partitioning,
child: SparkPlan,
- canChangeNumPartitions: Boolean = true) extends ShuffleExchangeLike {
+ isUserSpecifiedNumPartitions: Boolean = false) extends ShuffleExchangeLike
{
+
+ // If users specify the num partitions via APIs like `repartition`, we
shouldn't change it.
+ // For `SinglePartition`, it requires exactly one partition and we can't
change it either.
+ override def canChangeNumPartitions: Boolean =
+ !isUserSpecifiedNumPartitions && outputPartitioning != SinglePartition
Review comment:
This change is for future-proof. It doesn't change anything. When there
is a global aggregate, there will always be data in the final partition and we
can't coalesce to 0 partitions anyway.
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