Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/7417#discussion_r38678714
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/CartesianProduct.scala
---
@@ -27,16 +27,27 @@ import org.apache.spark.sql.execution.{BinaryNode,
SparkPlan}
* :: DeveloperApi ::
*/
@DeveloperApi
-case class CartesianProduct(left: SparkPlan, right: SparkPlan) extends
BinaryNode {
+case class CartesianProduct(
+ left: SparkPlan,
+ right: SparkPlan,
+ buildSide: BuildSide) extends BinaryNode {
override def output: Seq[Attribute] = left.output ++ right.output
+ private val (small, big) = buildSide match {
+ case BuildRight => (left, right)
+ case BuildLeft => (right, left)
+ }
+
protected override def doExecute(): RDD[InternalRow] = {
- val leftResults = left.execute().map(_.copy())
- val rightResults = right.execute().map(_.copy())
+ val leftResults = small.execute().map(_.copy())
+ val rightResults = big.execute().map(_.copy())
--- End diff --
As comment by @zsxwing , the right side will be iterated multiple times by
CartesianRDD, so it make sense to having small on the right side. We could even
load all the items on right side into memory as Array, we could do this if each
partition of `small` could fit in memory.
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