[SPARK-8636] [SQL] Fix equalNullSafe comparison

Author: Vinod K C <vinod.kc@huawei.com>

Closes #7040 from vinodkc/fix_CaseKeyWhen_equalNullSafe and squashes the following commits:

be5e641 [Vinod K C] Renamed equalNullSafe to threeValueEquals
aac9f67 [Vinod K C] Updated test suite and genCode method
f2d0b53 [Vinod K C]  Fix equalNullSafe comparison

2 files changed, 6 insertions, 9 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionals.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionals.scala
index e6a705fb80..84c28c27f9 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionals.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionals.scala
@@ -238,7 +238,7 @@ case class CaseKeyWhen(key: Expression, branches: Seq[Expression]) extends CaseW
     // If all branches fail and an elseVal is not provided, the whole statement
     // defaults to null, according to Hive's semantics.
     while (i < len - 1) {
-      if (equalNullSafe(evaluatedKey, branchesArr(i).eval(input))) {
+      if (threeValueEquals(evaluatedKey, branchesArr(i).eval(input))) {
         return branchesArr(i + 1).eval(input)
       }
       i += 2
@@ -261,8 +261,7 @@ case class CaseKeyWhen(key: Expression, branches: Seq[Expression]) extends CaseW
       s"""
         if (!$got) {
           ${cond.code}
-          if (${keyEval.isNull} && ${cond.isNull} ||
-            !${keyEval.isNull} && !${cond.isNull}
+          if (!${keyEval.isNull} && !${cond.isNull}
              && ${ctx.genEqual(key.dataType, keyEval.primitive, cond.primitive)}) {
             $got = true;
             ${res.code}
@@ -296,10 +295,8 @@ case class CaseKeyWhen(key: Expression, branches: Seq[Expression]) extends CaseW
     """
   }
 
-  private def equalNullSafe(l: Any, r: Any) = {
-    if (l == null && r == null) {
-      true
-    } else if (l == null || r == null) {
+  private def threeValueEquals(l: Any, r: Any) = {
+    if (l == null || r == null) {
       false
     } else {
       l == r
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ConditionalExpressionSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ConditionalExpressionSuite.scala
index aaf40cc83e..adadc8c54f 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ConditionalExpressionSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ConditionalExpressionSuite.scala
@@ -125,7 +125,7 @@ class ConditionalExpressionSuite extends SparkFunSuite with ExpressionEvalHelper
     val literalString = Literal("a")
 
     checkEvaluation(CaseKeyWhen(c1, Seq(c2, c4, c5)), "b", row)
-    checkEvaluation(CaseKeyWhen(c1, Seq(c2, c4, literalNull, c5, c6)), "b", row)
+    checkEvaluation(CaseKeyWhen(c1, Seq(c2, c4, literalNull, c5, c6)), "c", row)
     checkEvaluation(CaseKeyWhen(c2, Seq(literalInt, c4, c5)), "a", row)
     checkEvaluation(CaseKeyWhen(c2, Seq(c1, c4, c5)), "b", row)
     checkEvaluation(CaseKeyWhen(c4, Seq(literalString, c2, c3)), 1, row)
@@ -134,7 +134,7 @@ class ConditionalExpressionSuite extends SparkFunSuite with ExpressionEvalHelper
     checkEvaluation(CaseKeyWhen(literalInt, Seq(c2, c4, c5)), "a", row)
     checkEvaluation(CaseKeyWhen(literalString, Seq(c5, c2, c4, c3)), 2, row)
     checkEvaluation(CaseKeyWhen(c6, Seq(c5, c2, c4, c3)), null, row)
-    checkEvaluation(CaseKeyWhen(literalNull, Seq(c2, c5, c1, c6)), "c", row)
+    checkEvaluation(CaseKeyWhen(literalNull, Seq(c2, c5, c1, c6)), null, row)
   }
 
   test("function least") {