Github user markhamstra commented on a diff in the pull request:
https://github.com/apache/spark/pull/3632#discussion_r22420650
--- Diff: core/src/main/scala/org/apache/spark/util/Ordering.scala ---
@@ -0,0 +1,42 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.util
+
+private[spark] class HashOrdering[A] extends Ordering[A] {
+ override def compare(x: A, y: A): Int = {
+ val h1 = if (x == null) 0 else x.hashCode()
+ val h2 = if (y == null) 0 else y.hashCode()
+ if (h1 < h2) -1 else if (h1 == h2) 0 else 1
+ }
+}
+
+private[spark] class NoOrdering[A] extends Ordering[A] {
+ override def compare(x: A, y: A): Int = 0
+}
+
+private[spark] class KeyValueOrdering[A, B](
+ ordering1: Option[Ordering[A]], ordering2: Option[Ordering[B]]
+) extends Ordering[Product2[A, B]] {
+ private val ord1 = ordering1.getOrElse(new HashOrdering[A])
+ private val ord2 = ordering2.getOrElse(new NoOrdering[B])
--- End diff --
What is the expected scenario in which a `KeyValueOrdering` is called for
with `B` unordered? You're setting up `KeyValueOrdering` to be more general
than your needs for its only current usage in `OrderedValueRDDFunctions`, but
I'm not quite grasping how and where else you are expecting `KeyValueOrdering`
to be used.
It's seeming to me that `KeyValueOrdering` should have two ctors:
```scala
KeyValueOrdering[A, B](keyOrdering: Ordering[A], valueOrdering: Ordering[B])
...
this(valueOrdering: Ordering[B]) = this(new HashOrdering[A], valueOrdering)
```
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