SortOrder should not be foldable.

Author: rxin

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SortOrder.scala

@@ -32,6 +32,9 @@ case object Descending extends SortDirection
  */
 case class SortOrder(child: Expression, direction: SortDirection) extends UnaryExpression {
 
+  /** Sort order is not foldable because we don't have an eval for it. */
+  override def foldable: Boolean = false
+
   override def dataType: DataType = child.dataType
   override def nullable: Boolean = child.nullable
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala

@@ -127,6 +127,4 @@ case class Explode(child: Expression) extends UnaryExpression with Generator {
         else inputMap.map { case (k, v) => InternalRow(k, v) }
     }
   }
-
-  override def toString: String = s"explode($child)"
 }