From cb9fc8d9b6d385c9d193801edaea2d52e29a90fb Mon Sep 17 00:00:00 2001
From: Kazuaki Ishizaki <ishizaki@jp.ibm.com>
Date: Thu, 21 Dec 2017 14:54:38 +0800
Subject: [PATCH] [SPARK-22848][SQL] Eliminate mutable state from Stack

## What changes were proposed in this pull request?

This PR eliminates mutable states from the generated code for `Stack`.

## How was this patch tested?

Existing test suites

Author: Kazuaki Ishizaki <ishizaki@jp.ibm.com>

Closes #20035 from kiszk/SPARK-22848.
---
 .../spark/sql/catalyst/expressions/generators.scala    | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
index 1cd73a92a8635..69af7a250a5ac 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
@@ -214,11 +214,11 @@ case class Stack(children: Seq[Expression]) extends Generator {
 
     // Create the collection.
     val wrapperClass = classOf[mutable.WrappedArray[_]].getName
-    ctx.addMutableState(
-      s"$wrapperClass<InternalRow>",
-      ev.value,
-      v => s"$v = $wrapperClass$$.MODULE$$.make($rowData);", useFreshName = false)
-    ev.copy(code = code, isNull = "false")
+    ev.copy(code =
+      s"""
+         |$code
+         |$wrapperClass<InternalRow> ${ev.value} = $wrapperClass$$.MODULE$$.make($rowData);
+       """.stripMargin, isNull = "false")
   }
 }