HADOOP-7183. svn merge -c 1100056 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.21@1100058 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -54,6 +54,9 @@ Release 0.21.1 - Unreleased
     HADOOP-7194. Fix resource leak in IOUtils.copyBytes(..).
     (Devaraj K via szetszwo)
 
+    HADOOP-7183. WritableComparator.get should not cache comparator objects.
+    (tomwhite via eli)
+
 Release 0.21.0 - 2010-08-13
 
   INCOMPATIBLE CHANGES

src/java/org/apache/hadoop/io/WritableComparator.java

@@ -53,7 +53,6 @@ public class WritableComparator implements RawComparator {
       // if not, use the generic one
       if (comparator == null) {
         comparator = new WritableComparator(c, true);
-        comparators.put(c, comparator);
       }
     }
     return comparator;
@@ -75,7 +74,8 @@ public class WritableComparator implements RawComparator {
   } 
 
   /** Register an optimized comparator for a {@link WritableComparable}
-   * implementation. */
+   * implementation. Comparators registered with this method must be
+   * thread-safe. */
   public static synchronized void define(Class c,
                                          WritableComparator comparator) {
     comparators.put(c, comparator);