Github user cenyuhai commented on a diff in the pull request:
https://github.com/apache/spark/pull/19756#discussion_r151611386
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/Exchange.scala
---
@@ -109,3 +109,67 @@ case class ReuseExchange(conf: SQLConf) extends
Rule[SparkPlan] {
}
}
}
+
+/**
+ * Find out duplicated coordinated exchanges in the spark plan, then use
the same exchange for all
+ * the references.
+ */
+case class ReuseExchangeWithCoordinator(conf: SQLConf) extends
Rule[SparkPlan] {
+
+ // Returns true if a SparkPlan has coordinated ShuffleExchangeExec
children.
+ private def hasCoordinatedExchanges(plan: SparkPlan): Boolean = {
+ plan.children.nonEmpty && plan.children.forall {
+ case ShuffleExchangeExec(_, _, Some(_)) => true
+ case _ => false
+ }
+ }
+
+ // Returns true if two sequences of exchanges are producing the same
results.
+ private def hasExchangesWithSameResults(
+ source: Seq[ShuffleExchangeExec],
+ target: Seq[ShuffleExchangeExec]): Boolean = {
+ source.length == target.length &&
+ source.zip(target).forall(x =>
x._1.withoutCoordinator.sameResult(x._2.withoutCoordinator))
+ }
+
+ type CoordinatorSignature = (Int, Long, Option[Int])
+
+ def apply(plan: SparkPlan): SparkPlan = {
+ if (!conf.exchangeReuseEnabled) {
--- End diff --
exchangeReuseEnabled still has a bug: SPARK-20295, can we use a new
configuration?
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