Index: lucene/src/java/org/apache/lucene/search/CachingWrapperFilter.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/CachingWrapperFilter.java	(revision 1213973)
+++ lucene/src/java/org/apache/lucene/search/CachingWrapperFilter.java	(working copy)
@@ -25,6 +25,7 @@
 import org.apache.lucene.index.IndexReader.AtomicReaderContext;
 import org.apache.lucene.util.FixedBitSet;
 import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.IdentityKeyWrapper;
 
 /**
  * Wraps another filter's result and caches it.  The purpose is to allow
@@ -37,29 +38,26 @@
   // level of the readers hierarchy it should be cached.
   Filter filter;
 
-  protected final FilterCache<DocIdSet> cache;
+  protected final FilterCache cache = new FilterCache();
   private final boolean recacheDeletes;
 
-  private static class FilterCache<T> {
+  private static class FilterCache {
+    private final Map<Object,Map<IdentityKeyWrapper<Bits>,DocIdSet>> cache = new WeakHashMap<Object,Map<IdentityKeyWrapper<Bits>,DocIdSet>>();
 
-    /**
-     * A transient Filter cache (package private because of test)
-     */
-    private final Map<Object,Map<Object,T>> cache = new WeakHashMap<Object,Map<Object,T>>();
-
-    public synchronized T get(IndexReader reader, Object coreKey, Object coreSubKey) throws IOException {
-      Map<Object,T> innerCache = cache.get(coreKey);
+    public synchronized DocIdSet get(IndexReader reader, Object coreKey, Bits coreSubKey) throws IOException {
+      Map<IdentityKeyWrapper<Bits>,DocIdSet> innerCache = cache.get(coreKey);
       if (innerCache == null) {
-        innerCache = new WeakHashMap<Object,T>();
+        innerCache = new WeakHashMap<IdentityKeyWrapper<Bits>,DocIdSet>();
         cache.put(coreKey, innerCache);
       }
 
-      return innerCache.get(coreSubKey);
+      return innerCache.get(new IdentityKeyWrapper<Bits>(coreSubKey));
     }
 
-    public synchronized void put(Object coreKey, Object coreSubKey, T value) {
-      cache.get(coreKey).put(coreSubKey, value);
+    public synchronized void put(Object coreKey, Bits coreSubKey, DocIdSet value) {
+      cache.get(coreKey).put(new IdentityKeyWrapper<Bits>(coreSubKey), value);
     }
+    
   }
 
   /** Wraps another filter's result and caches it.
@@ -79,7 +77,6 @@
   public CachingWrapperFilter(Filter filter, boolean recacheDeletes) {
     this.filter = filter;
     this.recacheDeletes = recacheDeletes;
-    cache = new FilterCache<DocIdSet>();
   }
 
   /** Provide the DocIdSet to be cached, using the DocIdSet provided
Index: lucene/src/java/org/apache/lucene/util/IdentityKeyWrapper.java
===================================================================
--- lucene/src/java/org/apache/lucene/util/IdentityKeyWrapper.java	(revision 0)
+++ lucene/src/java/org/apache/lucene/util/IdentityKeyWrapper.java	(working copy)
@@ -0,0 +1,65 @@
+package org.apache.lucene.util;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * Helper class to wrap a key for a {@link java.util.Map} to be an identity key.
+ * You have to wrap the key on both puts and gets from the map.
+ * The map then behaves like {@link java.util.IdentityHashMap}
+ * (returns only the value if the wrapped key is <em>identical</em> to the one
+ * stored in the map (in contrast to <em>equal</em>). The {@code null} key
+ * is supported and is identical to itsself.
+ * It is generally used, if the user needs another map implementation than
+ * a simple hashed map, e.g. a {@link java.util.WeakHashMap}:
+ * <pre class="prettyprint language-java">
+ *  WeakHashMap&lt;IdentityKeyWrapper&lt;String&gt;,String&gt; map = ...
+ *  String key1 = "foo".intern();
+ *  String key2 = new String("foo");
+ *  String key3 = new String("foo");
+ *  assert key1 != key2;
+ *  assert key2 != key3;
+ *  map.put(new IdentityKeyWrapper&lt;String&gt;(key1), "bar1");
+ *  map.put(new IdentityKeyWrapper&lt;String&gt;(key2), "bar2");
+ *  assert "bar1".equals(map.get(new IdentityKeyWrapper&lt;String&gt;(key1)));
+ *  assert "bar2".equals(map.get(new IdentityKeyWrapper&lt;String&gt;(key2)));
+ *  assert map.get(new IdentityKeyWrapper&lt;String&gt;(key3)) == null;
+ * </pre>
+ * @lucene.internal
+ */
+public final class IdentityKeyWrapper<K> {
+  public final K key;
+
+  public IdentityKeyWrapper(K key) {
+    this.key = key;
+  }
+
+  public int hashCode() {
+    return System.identityHashCode(key);
+  }
+
+  @SuppressWarnings("unchecked")
+  public boolean equals(Object o) {
+    if (o == this) return true;
+    if (o instanceof IdentityKeyWrapper) {
+      return ((IdentityKeyWrapper<K>) o).key == this.key;
+    }
+    return false;
+  }
+
+}
+
Index: lucene/src/java/org/apache/lucene/util/IdentityKeyWrapper.java
===================================================================
--- lucene/src/java/org/apache/lucene/util/IdentityKeyWrapper.java	(revision 0)
+++ lucene/src/java/org/apache/lucene/util/IdentityKeyWrapper.java	(working copy)

Property changes on: lucene/src/java/org/apache/lucene/util/IdentityKeyWrapper.java
___________________________________________________________________
Added: svn:keywords
## -0,0 +1 ##
+Date Author Id Revision HeadURL
Added: svn:eol-style
## -0,0 +1 ##
+native
Index: lucene/src/test/org/apache/lucene/util/TestIdentityKeyWrapper.java
===================================================================
--- lucene/src/test/org/apache/lucene/util/TestIdentityKeyWrapper.java	(revision 0)
+++ lucene/src/test/org/apache/lucene/util/TestIdentityKeyWrapper.java	(working copy)
@@ -0,0 +1,57 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.util;
+
+import java.util.Map;
+import java.util.WeakHashMap;
+
+public class TestIdentityKeyWrapper extends LuceneTestCase {
+
+  public void test() {
+    final Map<IdentityKeyWrapper<String>,String> map =
+      new WeakHashMap<IdentityKeyWrapper<String>,String>();
+    // we keep strong values of the keys, so WeakHashMap will loose them
+    String key1 = "foo".intern();
+    String key2 = new String("foo");
+    String key3 = new String("foo");
+    assertNotSame(key1, key2);
+    assertNotSame(key1, key3);
+    assertNotSame(key2, key3);
+
+    assertEquals(new IdentityKeyWrapper<String>(key1), new IdentityKeyWrapper<String>(key1));
+    assertEquals(new IdentityKeyWrapper<String>(key2), new IdentityKeyWrapper<String>(key2));
+    assertEquals(new IdentityKeyWrapper<String>(key3), new IdentityKeyWrapper<String>(key3));
+    assertEquals(new IdentityKeyWrapper<String>(key1).hashCode(), new IdentityKeyWrapper<String>(key1).hashCode());
+    assertEquals(new IdentityKeyWrapper<String>(key2).hashCode(), new IdentityKeyWrapper<String>(key2).hashCode());
+    assertEquals(new IdentityKeyWrapper<String>(key3).hashCode(), new IdentityKeyWrapper<String>(key3).hashCode());
+
+    assertFalse(new IdentityKeyWrapper<String>(key1).equals(new IdentityKeyWrapper<String>(key2)));
+    assertFalse(new IdentityKeyWrapper<String>(key1).equals(new IdentityKeyWrapper<String>(key3)));
+    assertFalse(new IdentityKeyWrapper<String>(key2).equals(new IdentityKeyWrapper<String>(key3)));
+    assertTrue(new IdentityKeyWrapper<String>(key1).hashCode() != new IdentityKeyWrapper<String>(key2).hashCode());
+    assertTrue(new IdentityKeyWrapper<String>(key1).hashCode() != new IdentityKeyWrapper<String>(key3).hashCode());
+    assertTrue(new IdentityKeyWrapper<String>(key2).hashCode() != new IdentityKeyWrapper<String>(key3).hashCode());
+
+    map.put(new IdentityKeyWrapper<String>(key1), "bar1");
+    map.put(new IdentityKeyWrapper<String>(key2), "bar2");
+    assertEquals("bar1", map.get(new IdentityKeyWrapper<String>(key1)));
+    assertEquals("bar2", map.get(new IdentityKeyWrapper<String>(key2)));
+    assertFalse(map.containsKey(new IdentityKeyWrapper<String>(key3)));
+  }
+
+}
Index: lucene/src/test/org/apache/lucene/util/TestIdentityKeyWrapper.java
===================================================================
--- lucene/src/test/org/apache/lucene/util/TestIdentityKeyWrapper.java	(revision 0)
+++ lucene/src/test/org/apache/lucene/util/TestIdentityKeyWrapper.java	(working copy)

Property changes on: lucene/src/test/org/apache/lucene/util/TestIdentityKeyWrapper.java
___________________________________________________________________
Added: svn:keywords
## -0,0 +1 ##
+Date Author Id Revision HeadURL
Added: svn:eol-style
## -0,0 +1 ##
+native