Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/7774#discussion_r35837036
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/BroadcastHashOuterJoin.scala
---
@@ -57,13 +57,26 @@ case class BroadcastHashOuterJoin(
override def requiredChildDistribution: Seq[Distribution] =
UnspecifiedDistribution :: UnspecifiedDistribution :: Nil
+ /**
+ * Use lazy so that we won't do broadcast when calling explain but still
cache the broadcast value
+ * for the same query.
+ */
@transient
- private val broadcastFuture = future {
- // Note that we use .execute().collect() because we don't want to
convert data to Scala types
- val input: Array[InternalRow] =
buildPlan.execute().map(_.copy()).collect()
- val hashed = HashedRelation(input.iterator, buildKeyGenerator,
input.size)
- sparkContext.broadcast(hashed)
- }(BroadcastHashOuterJoin.broadcastHashOuterJoinExecutionContext)
+ private lazy val broadcastFuture = {
--- End diff --
Although @mateiz removed `lazy` in #1990, I want to add it back here.
Because without `lazy`, if the user runs `explain`, the `broadcastFuture` will
run and I cannot track the job.
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