diff --git a/contrib/benchmark/CHANGES.txt b/contrib/benchmark/CHANGES.txt
index 1f4ac0115f0..f0212f5d821 100644
--- a/contrib/benchmark/CHANGES.txt
+++ b/contrib/benchmark/CHANGES.txt
@@ -3,6 +3,15 @@ Lucene Benchmark Contrib Change Log
 The Benchmark contrib package contains code for benchmarking Lucene in a variety of ways.
 
 $Id:$
+6/12/09 
+  LUCENE-1539: Added DeleteByPercentTask which enables deleting a
+  percentage of documents and searching on them.  Changed CommitIndex
+  to optionally accept a label (recorded as userData=<label> in the
+  commit point).  Added FlushReaderTask, and modified OpenReaderTask
+  to also optionally take a label referencing a commit point to open.
+  Also changed default autoCommit (when IndexWriter is opened) to
+  true. (Jason Rutherglen via Mike McCandless)
+
 12/20/08
   LUCENE-1495: Allow task sequence to run for specfied number of seconds by adding ": 2.7s" (for example).
 
diff --git a/contrib/benchmark/conf/deletepercent.alg b/contrib/benchmark/conf/deletepercent.alg
new file mode 100644
index 00000000000..66d87cf3603
--- /dev/null
+++ b/contrib/benchmark/conf/deletepercent.alg
@@ -0,0 +1,105 @@
+#/**
+# * 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.
+# */
+# -------------------------------------------------------------------------------------
+# multi val params are iterated by NewRound's, added to reports, start with column name.
+
+autocommit=false
+analyzer=org.apache.lucene.analysis.standard.StandardAnalyzer
+directory=FSDirectory
+#directory=RamDirectory
+
+doc.stored=true
+doc.tokenized=true
+doc.term.vector=false
+doc.add.log.step=500
+
+docs.dir=reuters-out
+#docs.dir=reuters-111
+
+#doc.maker=org.apache.lucene.benchmark.byTask.feeds.SimpleDocMaker
+doc.maker=org.apache.lucene.benchmark.byTask.feeds.ReutersDocMaker
+
+#query.maker=org.apache.lucene.benchmark.byTask.feeds.SimpleQueryMaker
+query.maker=org.apache.lucene.benchmark.byTask.feeds.ReutersQueryMaker
+deletion.policy=org.apache.lucene.benchmark.utils.NoDeletionPolicy
+
+# task at this depth or less would print when they start
+task.max.depth.log=2
+
+log.queries=true
+# -------------------------------------------------------------------------------------
+
+{ "Rounds"
+
+    ResetSystemErase
+
+    { "Populate"
+        -CreateIndex
+        { "MAddDocs" AddDoc > : 1000
+        CommitIndex(original)
+        CloseIndex
+    }
+
+    OpenReader(false,original)
+    DeleteByPercent(5)
+    { "SearchSameRdr5" Search > : 500
+    FlushReader(5%)
+    CloseReader 
+    PrintReader(5%)
+
+    OpenReader(false,5%)
+    DeleteByPercent(10)
+    { "SearchSameRdr10" Search > : 500
+    FlushReader(10%)
+    CloseReader 
+    PrintReader(10%)
+
+    OpenReader(false,10%)
+    DeleteByPercent(20)
+    { "SearchSameRdr20" Search > : 500
+    FlushReader(20%)
+    CloseReader 
+    PrintReader(20%)
+    
+    OpenReader(false,20%)
+    DeleteByPercent(60)
+    { "SearchSameRdr60" Search > : 500
+    FlushReader(60%)
+    CloseReader 
+    PrintReader(60%)
+    
+    OpenReader(false,60%)
+    DeleteByPercent(75)
+    { "SearchSameRdr75" Search > : 500
+    FlushReader(75%)
+    CloseReader 
+    PrintReader(75%)
+
+    # Test lower percentage of deletes (so undeleteAll is used)
+    OpenReader(false,75%)
+    DeleteByPercent(7)
+    { "SearchSameRdr7" Search > : 500
+    FlushReader(7%)
+    CloseReader 
+    PrintReader(7%)
+
+    NewRound
+
+} : 1
+
+RepSumByName
+RepSumByPrefRound MAddDocs
diff --git a/contrib/benchmark/conf/indexing-multithreaded.alg b/contrib/benchmark/conf/indexing-multithreaded.alg
index 8e4bda0e678..dda0a287716 100644
--- a/contrib/benchmark/conf/indexing-multithreaded.alg
+++ b/contrib/benchmark/conf/indexing-multithreaded.alg
@@ -55,6 +55,7 @@ log.queries=true
         CreateIndex
         [{ "MAddDocs" AddDoc } : 5000] : 4
         Optimize
+        CommitIndex(commit1)
         CloseIndex
     }
 
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/AddDocTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/AddDocTask.java
index 4af39963641..5e1504678b6 100644
--- a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/AddDocTask.java
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/AddDocTask.java
@@ -76,7 +76,7 @@ public class AddDocTask extends PerfTask {
     return 1;
   }
 
-  private void log (int count) {
+  protected void log (int count) {
     if (logStep<0) {
       // init once per instance
       logStep = getRunData().getConfig().get("doc.add.log.step",DEFAULT_ADD_DOC_LOG_STEP);
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CommitIndexTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CommitIndexTask.java
index 9d48ab6523d..ada9f029f3a 100644
--- a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CommitIndexTask.java
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CommitIndexTask.java
@@ -16,22 +16,40 @@ package org.apache.lucene.benchmark.byTask.tasks;
  * limitations under the License.
  */
 
+import java.util.HashMap;
+import java.util.Map;
+
 import org.apache.lucene.benchmark.byTask.PerfRunData;
 import org.apache.lucene.index.IndexWriter;
 
 /**
- * Commits the IndexReader.
+ * Commits the IndexWriter.
  *
  */
 public class CommitIndexTask extends PerfTask {
+  String commitUserData = null;
+  
   public CommitIndexTask(PerfRunData runData) {
     super(runData);
   }
-
+  
+  public boolean supportsParams() {
+    return true;
+  }
+  
+  public void setParams(String params) {
+    commitUserData = params;
+  }
+  
   public int doLogic() throws Exception {
     IndexWriter iw = getRunData().getIndexWriter();
-    if (iw!=null) {
-      iw.commit();
+    if (iw != null) {
+      if (commitUserData == null) iw.commit();
+      else {
+        Map map = new HashMap();
+        map.put(OpenReaderTask.USER_DATA, commitUserData);
+        iw.commit(map);
+      }
     }
     
     return 1;
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CreateIndexTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CreateIndexTask.java
index 72ec92e1164..2d991227219 100644
--- a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CreateIndexTask.java
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/CreateIndexTask.java
@@ -19,6 +19,7 @@ package org.apache.lucene.benchmark.byTask.tasks;
 
 import org.apache.lucene.benchmark.byTask.PerfRunData;
 import org.apache.lucene.benchmark.byTask.utils.Config;
+import org.apache.lucene.index.IndexDeletionPolicy;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.MergeScheduler;
 import org.apache.lucene.index.MergePolicy;
@@ -91,14 +92,38 @@ public class CreateIndexTask extends PerfTask {
       writer.setRAMBufferSizeMB(ramBuffer);
     }
   }
-
+  
+  public static IndexDeletionPolicy getIndexDeletionPolicy(Config config) {
+    String deletionPolicyName = config.get("deletion.policy", "org.apache.lucene.index.KeepOnlyLastCommitDeletionPolicy");
+    IndexDeletionPolicy indexDeletionPolicy = null;
+    RuntimeException err = null;
+    try {
+      indexDeletionPolicy = ((IndexDeletionPolicy) Class.forName(deletionPolicyName).newInstance());
+    } catch (IllegalAccessException iae) {
+      err = new RuntimeException("unable to instantiate class '" + deletionPolicyName + "' as IndexDeletionPolicy");
+      err.initCause(iae);
+    } catch (InstantiationException ie) {
+      err = new RuntimeException("unable to instantiate class '" + deletionPolicyName + "' as IndexDeletionPolicy");
+      err.initCause(ie);
+    } catch (ClassNotFoundException cnfe) {
+      err = new RuntimeException("unable to load class '" + deletionPolicyName + "' as IndexDeletionPolicy");
+      err.initCause(cnfe);
+    }
+    if (err != null)
+      throw err;
+    return indexDeletionPolicy;
+  }
+  
   public int doLogic() throws IOException {
     PerfRunData runData = getRunData();
     Config config = runData.getConfig();
+    
+    IndexDeletionPolicy indexDeletionPolicy = getIndexDeletionPolicy(config);
+    
     IndexWriter writer = new IndexWriter(runData.getDirectory(),
                                          runData.getConfig().get("autocommit", OpenIndexTask.DEFAULT_AUTO_COMMIT),
                                          runData.getAnalyzer(),
-                                         true);
+                                         true, indexDeletionPolicy);
     CreateIndexTask.setIndexWriterConfig(writer, config);
     runData.setIndexWriter(writer);
     return 1;
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/DeleteByPercentTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/DeleteByPercentTask.java
new file mode 100644
index 00000000000..47fd7c99277
--- /dev/null
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/DeleteByPercentTask.java
@@ -0,0 +1,82 @@
+package org.apache.lucene.benchmark.byTask.tasks;
+
+/**
+ * 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.
+ */
+
+import java.util.Random;
+
+import org.apache.lucene.benchmark.byTask.PerfRunData;
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.TermDocs;
+
+/**
+ * Deletes a percentage of documents from an index randomly
+ * over the number of documents.  The parameter, X, is in
+ * percent.  EG 50 means 1/2 of all documents will be
+ * deleted.
+ *
+ * <p><b>NOTE</b>: the param is an absolute percentage of
+ * maxDoc().  This means if you delete 50%, and then delete
+ * 50% again, the 2nd delete will do nothing.
+ */
+public class DeleteByPercentTask extends PerfTask {
+  double percent;
+  int numDeleted = 0;
+  Random random = new Random(System.currentTimeMillis());
+
+  public DeleteByPercentTask(PerfRunData runData) {
+    super(runData);
+  }
+  
+  public void setup() throws Exception {
+    super.setup();
+  }
+
+  public void setParams(String params) {
+    super.setParams(params);
+    percent = Double.parseDouble(params)/100;
+  }
+
+  public boolean supportsParams() {
+    return true;
+  }
+
+  public int doLogic() throws Exception {
+    IndexReader r = getRunData().getIndexReader();
+    int maxDoc = r.maxDoc();
+    int numDeleted = 0;
+    // percent is an absolute target:
+    int numToDelete = ((int) (maxDoc * percent)) - r.numDeletedDocs();
+    if (numToDelete < 0) {
+      r.undeleteAll();
+      numToDelete = (int) (maxDoc * percent);
+    }
+    while (numDeleted < numToDelete) {
+      double delRate = ((double) (numToDelete-numDeleted))/r.numDocs();
+      TermDocs termDocs = r.termDocs(null);
+      while (termDocs.next() && numDeleted < numToDelete) {
+        if (random.nextDouble() <= delRate) {
+          r.deleteDocument(termDocs.doc());
+          numDeleted++;
+        }
+      }
+      termDocs.close();
+    }
+    System.out.println("--> processed (delete) " + numDeleted + " docs");
+    return numDeleted;
+  }
+}
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/FlushReaderTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/FlushReaderTask.java
new file mode 100644
index 00000000000..d3271df4ebe
--- /dev/null
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/FlushReaderTask.java
@@ -0,0 +1,54 @@
+package org.apache.lucene.benchmark.byTask.tasks;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.lucene.benchmark.byTask.PerfRunData;
+import org.apache.lucene.index.IndexReader;
+
+public class FlushReaderTask extends PerfTask {
+  String userData = null;
+  
+  public FlushReaderTask(PerfRunData runData) {
+    super(runData);
+  }
+  
+  public boolean supportsParams() {
+    return true;
+  }
+  
+  public void setParams(String params) {
+    super.setParams(params);
+    userData = params;
+  }
+  
+  public int doLogic() throws IOException {
+    IndexReader reader = getRunData().getIndexReader();
+    if (userData != null) {
+      Map map = new HashMap();
+      map.put(OpenReaderTask.USER_DATA, userData);
+      reader.flush(map);
+    } else {
+      reader.flush();
+    }
+    return 1;
+  }
+}
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenIndexTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenIndexTask.java
index 84fd99c40e2..a304d0b3ffa 100644
--- a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenIndexTask.java
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenIndexTask.java
@@ -38,7 +38,7 @@ public class OpenIndexTask extends PerfTask {
   public static final int DEFAULT_MAX_FIELD_LENGTH = IndexWriter.DEFAULT_MAX_FIELD_LENGTH;
   public static final int DEFAULT_MERGE_PFACTOR = LogMergePolicy.DEFAULT_MERGE_FACTOR;
   public static final double DEFAULT_RAM_FLUSH_MB = (int) IndexWriter.DEFAULT_RAM_BUFFER_SIZE_MB;
-  public static final boolean DEFAULT_AUTO_COMMIT = true;
+  public static final boolean DEFAULT_AUTO_COMMIT = false;
 
   public OpenIndexTask(PerfRunData runData) {
     super(runData);
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenReaderTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenReaderTask.java
index 1f0c84823e2..efbe924b41f 100644
--- a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenReaderTask.java
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/OpenReaderTask.java
@@ -18,18 +18,26 @@ package org.apache.lucene.benchmark.byTask.tasks;
  */
 
 import java.io.IOException;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Map;
 
 import org.apache.lucene.benchmark.byTask.PerfRunData;
+import org.apache.lucene.benchmark.byTask.utils.Config;
+import org.apache.lucene.index.IndexCommit;
+import org.apache.lucene.index.IndexDeletionPolicy;
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.store.Directory;
 
 /**
  * Open an index reader.
  * <br>Other side effects: index redaer object in perfRunData is set.
+ * <br> Optional params readOnly,commitUserData eg. OpenReader(false,commit1)
  */
 public class OpenReaderTask extends PerfTask {
-
+  public static final String USER_DATA = "userData";
   private boolean readOnly = true;
+  private String commitUserData = null;
 
   public OpenReaderTask(PerfRunData runData) {
     super(runData);
@@ -37,14 +45,51 @@ public class OpenReaderTask extends PerfTask {
 
   public int doLogic() throws IOException {
     Directory dir = getRunData().getDirectory();
-    IndexReader reader = IndexReader.open(dir, readOnly);
-    getRunData().setIndexReader(reader);
+    Config config = getRunData().getConfig();
+    IndexReader r = null;
+    if (commitUserData != null) {
+      r = openCommitPoint(commitUserData, dir, config, readOnly);
+    } else {
+      IndexDeletionPolicy indexDeletionPolicy = CreateIndexTask.getIndexDeletionPolicy(config);
+      r = IndexReader.open(dir, indexDeletionPolicy, readOnly); 
+    }
+    System.out.println("--> openReader: "+r.getCommitUserData());
+    getRunData().setIndexReader(r);
     return 1;
   }
-
+ 
+  public static IndexReader openCommitPoint(String userData, Directory dir, Config config, boolean readOnly) throws IOException {
+    IndexReader r = null;
+    Collection commits = IndexReader.listCommits(dir);
+    Iterator i = commits.iterator();
+    while (i.hasNext()) {
+      IndexCommit ic = (IndexCommit)i.next();
+      Map map = ic.getUserData();
+      String ud = null;
+      if (map != null) {
+        ud = (String)map.get(USER_DATA);
+      }
+      if (ud != null && ud.equals(userData)) {
+        IndexDeletionPolicy indexDeletionPolicy = CreateIndexTask.getIndexDeletionPolicy(config);
+        r = IndexReader.open(ic, indexDeletionPolicy, readOnly);
+        break;
+      }
+    }
+    if (r == null) throw new IOException("cannot find commitPoint userData:"+userData);
+    return r;
+  }
+  
   public void setParams(String params) {
     super.setParams(params);
-    readOnly = Boolean.valueOf(params).booleanValue();
+    if (params != null) {
+      String[] split = params.split(",");
+      if (split.length > 0) {
+        readOnly = Boolean.valueOf(split[0]).booleanValue();
+      }
+      if (split.length > 1) {
+        commitUserData = split[1];
+      }
+    }
   }
 
   public boolean supportsParams() {
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/PrintReaderTask.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/PrintReaderTask.java
new file mode 100644
index 00000000000..b3f6158ef90
--- /dev/null
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/byTask/tasks/PrintReaderTask.java
@@ -0,0 +1,53 @@
+package org.apache.lucene.benchmark.byTask.tasks;
+
+/**
+ * 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.
+ */
+
+import org.apache.lucene.benchmark.byTask.PerfRunData;
+import org.apache.lucene.benchmark.byTask.utils.Config;
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.store.Directory;
+
+public class PrintReaderTask extends PerfTask {
+  private String userData = null;
+  
+  public PrintReaderTask(PerfRunData runData) {
+    super(runData);
+  }
+  
+  public void setParams(String params) {
+    super.setParams(params);
+    userData = params;
+  }
+  
+  public boolean supportsParams() {
+    return true;
+  }
+  
+  public int doLogic() throws Exception {
+    Directory dir = getRunData().getDirectory();
+    Config config = getRunData().getConfig();
+    IndexReader r = null;
+    if (userData == null) 
+      r = IndexReader.open(dir);
+    else
+      r = OpenReaderTask.openCommitPoint(userData, dir, config, true);
+    System.out.println("--> numDocs:"+r.numDocs()+" dels:"+r.numDeletedDocs());
+    r.close();
+    return 1;
+  }
+}
diff --git a/contrib/benchmark/src/java/org/apache/lucene/benchmark/utils/NoDeletionPolicy.java b/contrib/benchmark/src/java/org/apache/lucene/benchmark/utils/NoDeletionPolicy.java
new file mode 100644
index 00000000000..633a76692cb
--- /dev/null
+++ b/contrib/benchmark/src/java/org/apache/lucene/benchmark/utils/NoDeletionPolicy.java
@@ -0,0 +1,31 @@
+package org.apache.lucene.benchmark.utils;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+import java.util.List;
+
+import org.apache.lucene.index.IndexDeletionPolicy;
+
+public class NoDeletionPolicy implements IndexDeletionPolicy {
+  public void onCommit(List commits) throws IOException {    
+  }
+
+  public void onInit(List commits) throws IOException {    
+  }
+}