[GitHub] [spark] cloud-fan commented on a change in pull request #29485: [SPARK-32638][SQL] Corrects references when adding aliases in WidenSetOperationTypes

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

cloud-fan commented on a change in pull request #29485:
URL: https://github.com/apache/spark/pull/29485#discussion_r482949552



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
##########
@@ -385,12 +408,16 @@ object TypeCoercion {
     }
 
     /** Given a plan, add an extra project on top to widen some columns' data types. */
-    private def widenTypes(plan: LogicalPlan, targetTypes: Seq[DataType]): LogicalPlan = {
+    private def widenTypes(plan: LogicalPlan, targetTypes: Seq[DataType])
+      : (LogicalPlan, LogicalPlan) = {
       val casted = plan.output.zip(targetTypes).map {
-        case (e, dt) if e.dataType != dt => Alias(Cast(e, dt), e.name)()
-        case (e, _) => e
-      }
-      Project(casted, plan)
+        case (e, dt) if e.dataType != dt =>
+          val alias = Alias(Cast(e, dt), e.name)(exprId = e.exprId)
+          alias -> alias.newInstance()
+        case (e, _) =>
+          e -> e
+      }.unzip
+      Project(casted._1, plan) -> Project(casted._2, plan)

Review comment:
       what are we doing here?




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