Github user scwf commented on a diff in the pull request:
https://github.com/apache/spark/pull/3531#discussion_r21077554
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/basicOperators.scala ---
@@ -148,20 +148,15 @@ case class Limit(limit: Int, child: SparkPlan)
}
override def execute() = {
- val rdd: RDD[_ <: Product2[Boolean, Row]] = if (sortBasedShuffleOn) {
- child.execute().mapPartitions { iter =>
- iter.take(limit).map(row => (false, row.copy()))
+ if (sortBasedShuffleOn) {
+ child.execute().map(_.copy).coalesce(1).mapPartitions { iter =>
+ iter.take(limit)
--- End diff --
Hmm, I will try this. Actually i am not clear why we need ```copy``` here,
@rxin added it to fix a bug. Hi @rxin, can you explain this?
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