Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/10577#discussion_r48930874
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicOperators.scala
---
@@ -123,6 +115,35 @@ case class Except(left: LogicalPlan, right:
LogicalPlan) extends SetOperation(le
override def output: Seq[Attribute] = left.output
}
+/** Factory for constructing new `Unions` nodes. */
+object Union {
+ def apply(left: LogicalPlan, right: LogicalPlan): Union = {
+ Union (left :: right :: Nil)
+ }
+}
+
+case class Union(children: Seq[LogicalPlan]) extends LogicalPlan {
+
+ override def output: Seq[Attribute] = {
+ children.tail.foldLeft(children.head.output) { case (currentOutput,
child) =>
+ currentOutput.zip(child.output).map { case (a1, a2) =>
+ a1.withNullability(a1.nullable || a2.nullable)
+ }
+ }
+ }
+
+ override lazy val resolved: Boolean =
+ childrenResolved &&
+ children.forall(_.output.length == children.head.output.length) &&
+ children.forall(_.output.zip(children.head.output).forall {
--- End diff --
this nested forall is pretty confusing. I'd restructure this.
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