[SPARK-14528] [SQL] Fix same result of Union

## What changes were proposed in this pull request?

This PR fix resultResult() for Union.

## How was this patch tested?

Added regression test.

Author: Davies Liu <davies@databricks.com>

Closes #12295 from davies/fix_sameResult.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala

@@ -312,18 +312,17 @@ abstract class QueryPlan[PlanType <: QueryPlan[PlanType]] extends TreeNode[PlanT
   /** Args that have cleaned such that differences in expression id should not affect equality */
   protected lazy val cleanArgs: Seq[Any] = {
     def cleanArg(arg: Any): Any = arg match {
+      // Children are checked using sameResult above.
+      case tn: TreeNode[_] if containsChild(tn) => null
       case e: Expression => cleanExpression(e).canonicalized
       case other => other
     }
 
     productIterator.map {
-      // Children are checked using sameResult above.
-      case tn: TreeNode[_] if containsChild(tn) => null
-      case e: Expression => cleanArg(e)
       case s: Option[_] => s.map(cleanArg)
       case s: Seq[_] => s.map(cleanArg)
       case m: Map[_, _] => m.mapValues(cleanArg)
-      case other => other
+      case other => cleanArg(other)
     }.toSeq
   }
 }

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/plans/SameResultSuite.scala

@@ -20,7 +20,7 @@ package org.apache.spark.sql.catalyst.plans
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.catalyst.dsl.expressions._
 import org.apache.spark.sql.catalyst.dsl.plans._
-import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan}
+import org.apache.spark.sql.catalyst.plans.logical.{LocalRelation, LogicalPlan, Union}
 import org.apache.spark.sql.catalyst.util._
 
 /**
@@ -61,4 +61,9 @@ class SameResultSuite extends SparkFunSuite {
   test("sorts") {
     assertSameResult(testRelation.orderBy('a.asc), testRelation2.orderBy('a.asc))
   }
+
+  test("union") {
+    assertSameResult(Union(Seq(testRelation, testRelation2)),
+      Union(Seq(testRelation2, testRelation)))
+  }
 }