Github user dbtsai commented on a diff in the pull request:
https://github.com/apache/spark/pull/11242#discussion_r56719728
--- Diff: core/src/main/scala/org/apache/spark/rdd/UnionRDD.scala ---
@@ -62,7 +64,23 @@ class UnionRDD[T: ClassTag](
var rdds: Seq[RDD[T]])
extends RDD[T](sc, Nil) { // Nil since we implement getDependencies
+ // Evaluate partitions in parallel. Partitions of each rdd will be
cached by the `partitions`
+ // val in `RDD`.
+ private[spark] lazy val parallelPartitionEval: Boolean = {
+ val threshold = conf.getInt("spark.rdd.parallelListingThreshold", 10)
+ if (threshold > 0 && rdds.length > threshold) {
+ val parArray = rdds.toParArray
+ parArray.tasksupport = new ForkJoinTaskSupport(
+ new ForkJoinPool(math.min(threshold, 8)))
--- End diff --
In this case, it will always be 8 threads by default. How about
```scala
private[spark] lazy val parallelPartitionEval: Boolean = {
val parallelism = conf.getInt("spark.rdd.listingParallelism", 16)
val threshold = 8
if (rdds.length > threshold) {
val parArray = rdds.toParArray
parArray.tasksupport = new ForkJoinTaskSupport(
new ForkJoinPool(math.min(parallelism, rdds.length)))
parArray.foreach(_.partitions)
true
} else {
false
}
}
```
Thanks.
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