Github user scwf commented on a diff in the pull request:
https://github.com/apache/spark/pull/7417#discussion_r34749244
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/CartesianProduct.scala
---
@@ -34,7 +34,15 @@ case class CartesianProduct(left: SparkPlan, right:
SparkPlan) extends BinaryNod
val leftResults = left.execute().map(_.copy())
val rightResults = right.execute().map(_.copy())
- leftResults.cartesian(rightResults).mapPartitions { iter =>
+ val cartesianRdd = if (leftResults.partitions.size >
rightResults.partitions.size) {
+ rightResults.cartesian(leftResults).mapPartitions { iter =>
+ iter.map(tuple => (tuple._2, tuple._1))
+ }
+ } else {
+ leftResults.cartesian(rightResults)
+ }
+
+ cartesianRdd.mapPartitions { iter =>
val joinedRow = new JoinedRow
--- End diff --
yes, use partition size here is not accurate, see a rdd with 100
partitions, and each partition has one record and a rdd with 10 partition and
each partition has 100 million records, use the method above will cause more
scan from hdfs
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