From 7fccb0258ea1bc8fa952a5ebd629d1808ee4e6ee Mon Sep 17 00:00:00 2001
From: Michael Stack <stack@apache.org>
Date: Tue, 20 Jan 2009 06:37:29 +0000
Subject: [PATCH] HBASE-1134 HashFunction inadvertently destroys some
 randomness

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@735947 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES.txt                                  |  2 ++
 src/java/org/onelab/filter/HashFunction.java |  3 ++-
 src/test/org/onelab/test/TestFilter.java     | 15 ++-------------
 3 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index ebe750ee122..f414e543846 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -5,6 +5,8 @@ Release 0.20.0 - Unreleased
   BUG FIXES
    HBASE-1140  "ant clean test" fails (Nitay Joffe via Stack)
    HBASE-1129  Master won't go down; stuck joined on rootScanner
+   HBASE-1136  HashFunction inadvertently destroys some randomness
+               (Jonathan Ellis via Stack)
 
   IMPROVEMENTS
    HBASE-1089  Add count of regions on filesystem to master UI; add percentage
diff --git a/src/java/org/onelab/filter/HashFunction.java b/src/java/org/onelab/filter/HashFunction.java
index a0c26964e2f..cf97c7bcaa2 100644
--- a/src/java/org/onelab/filter/HashFunction.java
+++ b/src/java/org/onelab/filter/HashFunction.java
@@ -118,7 +118,8 @@ public final class HashFunction {
       }
       int[] result = new int[nbHash];
       for (int i = 0, initval = 0; i < nbHash; i++) {
-        initval = result[i] = Math.abs(hashFunction.hash(b, initval) % maxValue);
+	  initval = hashFunction.hash(b, initval);
+	  result[i] = Math.abs(initval) % maxValue;
       }
       return result;
   }//end hash() 
diff --git a/src/test/org/onelab/test/TestFilter.java b/src/test/org/onelab/test/TestFilter.java
index 6c88c1ab33f..eb04d1afd84 100644
--- a/src/test/org/onelab/test/TestFilter.java
+++ b/src/test/org/onelab/test/TestFilter.java
@@ -266,7 +266,7 @@ public class TestFilter extends TestCase {
    * @throws UnsupportedEncodingException
    */
   public void testCountingBloomFilter() throws UnsupportedEncodingException {
-    Filter bf = new CountingBloomFilter(8, 2, Hash.JENKINS_HASH);
+    Filter bf = new CountingBloomFilter(128, 2, Hash.JENKINS_HASH);
     Key key = new StringKey("toto");
     Key k2 = new StringKey("lulu");
     Key k3 = new StringKey("mama");
@@ -274,7 +274,6 @@ public class TestFilter extends TestCase {
     bf.add(k2);
     bf.add(k3);
     assertTrue(bf.membershipTest(key));
-    assertTrue(bf.membershipTest(new StringKey("graknyl")));
     assertFalse(bf.membershipTest(new StringKey("xyzzy")));
     assertFalse(bf.membershipTest(new StringKey("abcd")));
 
@@ -282,15 +281,6 @@ public class TestFilter extends TestCase {
     ((CountingBloomFilter)bf).delete(key);
     assertFalse(bf.membershipTest(key));
     
-    // OR 'key' back into the filter
-    Filter bf2 = new CountingBloomFilter(8, 2, Hash.JENKINS_HASH);
-    bf2.add(key);
-    bf.or(bf2);
-    assertTrue(bf.membershipTest(key));
-    assertTrue(bf.membershipTest(new StringKey("graknyl")));
-    assertFalse(bf.membershipTest(new StringKey("xyzzy")));
-    assertFalse(bf.membershipTest(new StringKey("abcd")));
-    
     // to test for overflows, add 'key' enough times to overflow a 4bit bucket,
     // while asserting that it stays a member
     for(int i = 0; i < 16; i++){
@@ -319,7 +309,7 @@ public class TestFilter extends TestCase {
    * @throws UnsupportedEncodingException
    */
   public void testDynamicBloomFilter() throws UnsupportedEncodingException {
-    Filter bf = new DynamicBloomFilter(8, 2, Hash.JENKINS_HASH, 2);
+    Filter bf = new DynamicBloomFilter(128, 2, Hash.JENKINS_HASH, 2);
     Key key = new StringKey("toto");
     Key k2 = new StringKey("lulu");
     Key k3 = new StringKey("mama");
@@ -327,7 +317,6 @@ public class TestFilter extends TestCase {
     bf.add(k2);
     bf.add(k3);
     assertTrue(bf.membershipTest(key));
-    assertTrue(bf.membershipTest(new StringKey("graknyl")));
     assertFalse(bf.membershipTest(new StringKey("xyzzy")));
     assertFalse(bf.membershipTest(new StringKey("abcd")));
   }