Github user markhamstra commented on a diff in the pull request:
https://github.com/apache/spark/pull/21754#discussion_r203416454
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/Exchange.scala
---
@@ -85,14 +85,20 @@ case class ReusedExchangeExec(override val output:
Seq[Attribute], child: Exchan
*/
case class ReuseExchange(conf: SQLConf) extends Rule[SparkPlan] {
+ private def supportReuseExchange(exchange: Exchange): Boolean = exchange
match {
+ // If a coordinator defined in an exchange operator, the exchange
cannot be reused
--- End diff --
This seems overstated if this comment in the JIRA description is correct:
"When the cache tabel device_loc is executed before this query is executed,
everything is fine". In fact, if Xiao Li is correct in that statement, then
this PR is eliminating a useful optimization in cases where it doesn't need to
-- i.e. it is preventing Exchange reuse any time adaptive execution is used
instead of only preventing reuse when it will actually cause a problem.
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