[GitHub] [spark] maropu commented on a change in pull request #29671: [SPARK-32817] DPP throws error when broadcast side is empty

[GitBox <gi...@apache.org>]

maropu commented on a change in pull request #29671:
URL: https://github.com/apache/spark/pull/29671#discussion_r484719996



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/SubqueryBroadcastExec.scala
##########
@@ -75,17 +75,21 @@ case class SubqueryBroadcastExec(
         val beforeCollect = System.nanoTime()
 
         val broadcastRelation = child.executeBroadcast[HashedRelation]().value
-        val (iter, expr) = if (broadcastRelation.isInstanceOf[LongHashedRelation]) {
-          (broadcastRelation.keys(), HashJoin.extractKeyExprAt(buildKeys, index))
-        } else {
-          (broadcastRelation.keys(),
-            BoundReference(index, buildKeys(index).dataType, buildKeys(index).nullable))
+        val rows = broadcastRelation match {
+          case EmptyHashedRelation =>
+            Array.empty[InternalRow]

Review comment:
       Ah, nice catch. We cannot just return an empty row in `EmptyHashedRelation.keys()`?
   ```
   case object EmptyHashedRelation extends HashedRelation {
     ...
     override def keys(): Iterator[InternalRow] = {
       Iterator.empty[InternalRow]
     }
   ```




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