HADOOP-4046. Merge -r 691305:691306 from trunk to branch 0.18

git-svn-id: https://svn.apache.org/repos/asf/hadoop/core/branches/branch-0.18@691308 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -14,6 +14,9 @@ Release 0.18.1 - Unreleased
     from the TaskTracker, which was causing HDFS client connections to not be 
     collected. (ddas via omalley)
 
+    HADOOP-4046. Made WritableComparable's constructor protected instead of 
+    private to re-enable class derivation. (cdouglas via omalley)
+
 Release 0.18.0 - 2008-08-19
 
   INCOMPATIBLE CHANGES

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

@@ -63,7 +63,7 @@ public class WritableComparator implements RawComparator {
     this(keyClass, false);
   }
 
-  private WritableComparator(Class keyClass, boolean createInstances) {
+  protected WritableComparator(Class keyClass, boolean createInstances) {
     this.keyClass = keyClass;
     if (createInstances) {
       key1 = newKey();

src/test/org/apache/hadoop/mapred/TestComparators.java

@@ -420,5 +420,48 @@ public class TestComparators extends TestCase
       fail("Oops! The job broke due to an unexpected error");
     }
   }
-  
+
+  /**
+   * Test a user comparator that relies on deserializing both arguments
+   * for each compare.
+   */
+  public void testBakedUserComparator() throws Exception {
+    MyWritable a = new MyWritable(8, 8);
+    MyWritable b = new MyWritable(7, 9);
+    assertTrue(a.compareTo(b) > 0);
+    assertTrue(WritableComparator.get(MyWritable.class).compare(a, b) < 0);
+  }
+
+  public static class MyWritable implements WritableComparable<MyWritable> {
+    int i, j;
+    public MyWritable() { }
+    public MyWritable(int i, int j) {
+      this.i = i;
+      this.j = j;
+    }
+    public void readFields(DataInput in) throws IOException {
+      i = in.readInt();
+      j = in.readInt();
+    }
+    public void write(DataOutput out) throws IOException {
+      out.writeInt(i);
+      out.writeInt(j);
+    }
+    public int compareTo(MyWritable b) {
+      return this.i - b.i;
+    }
+    static {
+      WritableComparator.define(MyWritable.class, new MyCmp());
+    }
+  }
+
+  public static class MyCmp extends WritableComparator {
+    public MyCmp() { super(MyWritable.class, true); }
+    public int compare(WritableComparable a, WritableComparable b) {
+      MyWritable aa = (MyWritable)a;
+      MyWritable bb = (MyWritable)b;
+      return aa.j - bb.j;
+    }
+  }
+
 }