MAPREDUCE-4272. SortedRanges.Range#compareTo is not spec compliant. (Yu Gao via llu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1425179 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -30,6 +30,9 @@ Release 2.0.3-alpha - Unreleased
 
   BUG FIXES
 
+    MAPREDUCE-4272. SortedRanges.Range#compareTo is not spec compliant.
+    (Yu Gao via llu)
+
     MAPREDUCE-4607. Race condition in ReduceTask completion can result in Task
     being incorrectly failed. (Bikas Saha via tomwhite)
 

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/SortedRanges.java

@@ -271,7 +271,7 @@ class SortedRanges implements Writable{
     }
     
     public boolean equals(Object o) {
-      if(o!=null && o instanceof Range) {
+      if (o instanceof Range) {
         Range range = (Range)o;
         return startIndex==range.startIndex &&
         length==range.length;
@@ -285,10 +285,11 @@ class SortedRanges implements Writable{
     }
     
     public int compareTo(Range o) {
-      if(this.equals(o)) {
-        return 0;
-      }
-      return (this.startIndex > o.startIndex) ? 1:-1;
+      // Ensure sgn(x.compareTo(y) == -sgn(y.compareTo(x))
+      return this.startIndex < o.startIndex ? -1 :
+          (this.startIndex > o.startIndex ? 1 :
+          (this.length < o.length ? -1 :
+          (this.length > o.length ? 1 : 0)));
     }
 
     public void readFields(DataInput in) throws IOException {