maryannxue commented on a change in pull request #24706: [SPARK-23128][SQL] A
new approach to do adaptive execution in Spark SQL
URL: https://github.com/apache/spark/pull/24706#discussion_r289145896
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/BroadcastExchangeExec.scala
##########
@@ -58,11 +58,21 @@ case class BroadcastExchangeExec(
BroadcastExchangeExec(mode.canonicalized, child.canonicalized)
}
+ @transient
+ private lazy val promise = Promise[broadcast.Broadcast[Any]]()
+
+ /**
+ * For registering callbacks on `relationFuture`.
+ * Note that calling this field will not start the execution of broadcast
job.
+ */
+ @transient
+ lazy val completionFuture: scala.concurrent.Future[broadcast.Broadcast[Any]]
= promise.future
+
@transient
private val timeout: Long = SQLConf.get.broadcastTimeout
@transient
- private lazy val relationFuture: Future[broadcast.Broadcast[Any]] = {
+ private[sql] lazy val relationFuture: Future[broadcast.Broadcast[Any]] = {
Review comment:
Yeah, just to include more info in our offline discussion here:
What is needed by AQE is a "cancellable" Future with callbacks.
Java Future is cancellable, but has no callbacks.
Scala Future has callbacks, but is not cancellable.
The Spark impl of a cancellable Scala Future (with callbacks), namely
`FutureAction`, is more specific for Spark jobs and for general purpose, thus
not so friendly to `BroadcastExchangeExec` here.
Looks like an option can be to implement a general purpose `FutureAction` to
replace the Java Future in `BroadcastExchangeExec`. Let's just mark this a
follow-up though.
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