cloud-fan commented on code in PR #50849:
URL: https://github.com/apache/spark/pull/50849#discussion_r2097526605
##########
sql/core/src/main/scala/org/apache/spark/sql/execution/ExistingRDD.scala:
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@@ -319,3 +319,46 @@ case class RDDScanExec(
override def getStream: Option[SparkDataStream] = stream
}
+
+/**
+ * A physical plan node for `OneRowRelation` for scans with no 'FROM' clause.
+ *
+ * We do not extend `RDDScanExec` in order to avoid complexity due to
`TreeNode.makeCopy` and
+ * `TreeNode`'s general use of reflection.
+ */
+case class OneRowRelationExec() extends LeafExecNode
+ with InputRDDCodegen {
+
+ override val nodeName: String = s"Scan OneRowRelation"
+
+ override val output: Seq[Attribute] = Nil
+
+ private val emptyRow: InternalRow = InternalRow.empty
+
+ private val rdd = session.sparkContext.parallelize(Seq(emptyRow), 1)
+
+ override lazy val metrics = Map(
+ "numOutputRows" -> SQLMetrics.createMetric(sparkContext, "number of output
rows"))
+
+ protected override def doExecute(): RDD[InternalRow] = {
+ val numOutputRows = longMetric("numOutputRows")
+ val proj = UnsafeProjection.create(schema)
+ val outputRow = proj(emptyRow)
+ rdd.mapPartitionsWithIndexInternal { (index, iter) =>
+ iter.map { r =>
+ numOutputRows += 1
+ outputRow
+ }
+ }
+ }
+
+ override def simpleString(maxFields: Int): String = s"$nodeName[]"
+
+ override def inputRDD: RDD[InternalRow] = rdd
+
+ override protected val createUnsafeProjection: Boolean = true
Review Comment:
If we do https://github.com/apache/spark/pull/50849/files#r2097521541 , then
this can be false.
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