From 4b3d1294aeecc0001a7fa48c92796e6075d34540 Mon Sep 17 00:00:00 2001
From: CodingCat <zhunansjtu@gmail.com>
Date: Mon, 18 Apr 2016 18:51:23 -0700
Subject: [PATCH] [SPARK-13227] Risky apply() in OpenHashMap

https://issues.apache.org/jira/browse/SPARK-13227

It might confuse the future developers when they use OpenHashMap.apply() with a numeric value type.

null.asInstance[Int], null.asInstance[Long], null.asInstace[Float] and null.asInstance[Double] will return 0/0.0/0L, which might confuse the developer if the value set contains 0/0.0/0L with an existing key

The current patch only adds the comments describing the issue, with the respect to apply the minimum changes to the code base

The more direct, yet more aggressive, approach is use Option as the return type

andrewor14  JoshRosen  any thoughts about how to avoid the potential issue?

Author: CodingCat <zhunansjtu@gmail.com>

Closes #11107 from CodingCat/SPARK-13227.
---
 .../scala/org/apache/spark/util/collection/OpenHashMap.scala   | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/core/src/main/scala/org/apache/spark/util/collection/OpenHashMap.scala b/core/src/main/scala/org/apache/spark/util/collection/OpenHashMap.scala
index 22d7a4988b..10ab0b3f89 100644
--- a/core/src/main/scala/org/apache/spark/util/collection/OpenHashMap.scala
+++ b/core/src/main/scala/org/apache/spark/util/collection/OpenHashMap.scala
@@ -25,6 +25,9 @@ import scala.reflect.ClassTag
  * space overhead.
  *
  * Under the hood, it uses our OpenHashSet implementation.
+ *
+ * NOTE: when using numeric type as the value type, the user of this class should be careful to
+ * distinguish between the 0/0.0/0L and non-exist value
  */
 private[spark]
 class OpenHashMap[K : ClassTag, @specialized(Long, Int, Double) V: ClassTag](
-- 
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