From bd837d47f7230798f2bb7ac18e711e8f265b167f Mon Sep 17 00:00:00 2001
From: tedyu <yuzhihong@gmail.com>
Date: Sat, 28 Mar 2015 06:31:28 -0700
Subject: [PATCH] HBASE-12413 Mismatch in the equals and hashcode methods of
 KeyValue (Jingcheng Du and Gariel Reid)

---
 .../apache/hadoop/hbase/CellComparator.java   |  4 +---
 .../org/apache/hadoop/hbase/KeyValue.java     | 11 ++++------
 .../org/apache/hadoop/hbase/TestKeyValue.java | 20 +++++++++++++++++++
 3 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/CellComparator.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/CellComparator.java
index cbb7ff3162b..540c967546e 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/CellComparator.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/CellComparator.java
@@ -244,7 +244,6 @@ public class CellComparator implements Comparator<Cell>, Serializable {
 
   /**
    * Returns a hash code that is always the same for two Cells having a matching equals(..) result.
-   * Currently does not guard against nulls, but it could if necessary.
    */
   public static int hashCode(Cell cell){
     if (cell == null) {// return 0 for empty Cell
@@ -258,8 +257,7 @@ public class CellComparator implements Comparator<Cell>, Serializable {
 
   /**
    * Returns a hash code that is always the same for two Cells having a matching
-   * equals(..) result. Currently does not guard against nulls, but it could if
-   * necessary. Note : Ignore mvcc while calculating the hashcode
+   * equals(..) result. Note : Ignore mvcc while calculating the hashcode
    * 
    * @param cell
    * @return hashCode
diff --git a/hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java b/hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java
index dace44c7e1d..7de1f54b0fb 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java
@@ -1064,15 +1064,12 @@ public class KeyValue implements Cell, HeapSize, Cloneable, SettableSequenceId,
     return CellComparator.equals(this, (Cell)other);
   }
 
+  /**
+   * In line with {@link #equals(Object)}, only uses the key portion, not the value.
+   */
   @Override
   public int hashCode() {
-    byte[] b = getBuffer();
-    int start = getOffset(), end = getOffset() + getLength();
-    int h = b[start++];
-    for (int i = start; i < end; i++) {
-      h = (h * 13) ^ b[i];
-    }
-    return h;
+    return CellComparator.hashCodeIgnoreMvcc(this);
   }
 
   //---------------------------------------------------------------------------
diff --git a/hbase-common/src/test/java/org/apache/hadoop/hbase/TestKeyValue.java b/hbase-common/src/test/java/org/apache/hadoop/hbase/TestKeyValue.java
index 0b67b415601..5daeefbe7c9 100644
--- a/hbase-common/src/test/java/org/apache/hadoop/hbase/TestKeyValue.java
+++ b/hbase-common/src/test/java/org/apache/hadoop/hbase/TestKeyValue.java
@@ -35,6 +35,8 @@ import org.apache.hadoop.hbase.KeyValue.MetaComparator;
 import org.apache.hadoop.hbase.KeyValue.Type;
 import org.apache.hadoop.hbase.util.Bytes;
 
+import static org.junit.Assert.assertNotEquals;
+
 public class TestKeyValue extends TestCase {
   private final Log LOG = LogFactory.getLog(this.getClass().getName());
 
@@ -614,4 +616,22 @@ public class TestKeyValue extends TestCase {
     b = new KeyValue(Bytes.toBytes("table,111,222,bbb"), now);
     assertTrue(c.compare(a, b) < 0);
   }
+
+  public void testEqualsAndHashCode() throws Exception {
+    KeyValue kvA1 = new KeyValue(Bytes.toBytes("key"), Bytes.toBytes("cf"),
+        Bytes.toBytes("qualA"), Bytes.toBytes("1"));
+    KeyValue kvA2 = new KeyValue(Bytes.toBytes("key"), Bytes.toBytes("cf"),
+        Bytes.toBytes("qualA"), Bytes.toBytes("2"));
+    // We set a different sequence id on kvA2 to demonstrate that the equals and hashCode also
+    // don't take this into account.
+    kvA2.setSequenceId(2);
+    KeyValue kvB = new KeyValue(Bytes.toBytes("key"), Bytes.toBytes("cf"),
+        Bytes.toBytes("qualB"), Bytes.toBytes("1"));
+
+    assertEquals(kvA1, kvA2);
+    assertNotEquals(kvA1, kvB);
+    assertEquals(kvA1.hashCode(), kvA2.hashCode());
+    assertNotEquals(kvA1.hashCode(), kvB.hashCode());
+
+  }
 }