Index: CHANGES.txt
===================================================================
--- CHANGES.txt	(revision 925469)
+++ CHANGES.txt	(working copy)
@@ -193,6 +193,12 @@
   documents (previously this was hardwired to 5), using
   IndexWriterConfig.setMaxThreadStates.  (Mike McCandless)
 
+* LUCENE-2331: Add NoMergePolicy which never returns any merges to execute. In
+  addition, add NoMergeScheduler which never executes any merges. These two are
+  convenient classes in case you want to disable segment merges by IndexWriter
+  without tweaking a particular MergePolicy parameters, such as mergeFactor.
+  MergeScheduler's methods are now public. (Shai Erera via ?)
+  
 Optimizations
 
 * LUCENE-2075: Terms dict cache is now shared across threads instead
Index: src/java/org/apache/lucene/index/MergeScheduler.java
===================================================================
--- src/java/org/apache/lucene/index/MergeScheduler.java	(revision 925469)
+++ src/java/org/apache/lucene/index/MergeScheduler.java	(working copy)
@@ -26,14 +26,13 @@
  *
  * @lucene.experimental
 */
-
 public abstract class MergeScheduler {
 
   /** Run the merges provided by {@link IndexWriter#getNextMerge()}. */
-  abstract void merge(IndexWriter writer)
+  public abstract void merge(IndexWriter writer)
     throws CorruptIndexException, IOException;
 
   /** Close this MergeScheduler. */
-  abstract void close()
+  public abstract void close()
     throws CorruptIndexException, IOException;
 }
Index: src/java/org/apache/lucene/index/NoMergePolicy.java
===================================================================
--- src/java/org/apache/lucene/index/NoMergePolicy.java	(revision 0)
+++ src/java/org/apache/lucene/index/NoMergePolicy.java	(revision 0)
@@ -0,0 +1,78 @@
+package org.apache.lucene.index;
+
+/**
+ * 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.Set;
+
+/**
+ * A {@link MergePolicy} which never returns merges to execute (hence it's
+ * name). It is also a singleton and can be accessed through
+ * {@link NoMergePolicy#NO_COMPOUND_FILES} if you want to indicate the index
+ * does not use compound files, or through {@link NoMergePolicy#COMPOUND_FILES}
+ * otherwise. Use it if you want to prevent an {@link IndexWriter} from ever
+ * executing merges, without going through the hassle of tweaking a merge
+ * policy's settings to achieve that, such as changing its merge factor.
+ */
+public final class NoMergePolicy extends MergePolicy {
+
+  /**
+   * A singleton {@link NoMergePolicy} which indicates the index does not use
+   * compound files.
+   */
+  public static final MergePolicy NO_COMPOUND_FILES = new NoMergePolicy(false);
+
+  /**
+   * A singleton {@link NoMergePolicy} which indicates the index uses compound
+   * files.
+   */
+  public static final MergePolicy COMPOUND_FILES = new NoMergePolicy(true);
+
+  private final boolean useCompoundFile;
+  
+  private NoMergePolicy(boolean useCompoundFile) {
+    // prevent instantiation
+    this.useCompoundFile = useCompoundFile;
+  }
+
+  @Override
+  public void close() {}
+
+  @Override
+  public MergeSpecification findMerges(SegmentInfos segmentInfos)
+      throws CorruptIndexException, IOException { return null; }
+
+  @Override
+  public MergeSpecification findMergesForOptimize(SegmentInfos segmentInfos,
+      int maxSegmentCount, Set<SegmentInfo> segmentsToOptimize)
+      throws CorruptIndexException, IOException { return null; }
+
+  @Override
+  public MergeSpecification findMergesToExpungeDeletes(SegmentInfos segmentInfos)
+      throws CorruptIndexException, IOException { return null; }
+
+  @Override
+  public boolean useCompoundDocStore(SegmentInfos segments) { return useCompoundFile; }
+
+  @Override
+  public boolean useCompoundFile(SegmentInfos segments, SegmentInfo newSegment) { return useCompoundFile; }
+
+  @Override
+  public void setIndexWriter(IndexWriter writer) {}
+
+}

Property changes on: src\java\org\apache\lucene\index\NoMergePolicy.java
___________________________________________________________________
Added: svn:keywords
   + Date Author Id Revision HeadURL
Added: svn:eol-style
   + native

Index: src/java/org/apache/lucene/index/NoMergeScheduler.java
===================================================================
--- src/java/org/apache/lucene/index/NoMergeScheduler.java	(revision 0)
+++ src/java/org/apache/lucene/index/NoMergeScheduler.java	(revision 0)
@@ -0,0 +1,47 @@
+package org.apache.lucene.index;
+
+/**
+ * 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;
+
+/**
+ * A {@link MergeScheduler} which never executes any merges. It is also a
+ * singleton and can be accessed through {@link NoMergeScheduler#INSTANCE}. Use
+ * it if you want to prevent an {@link IndexWriter} from ever executing merges,
+ * irregardles of the {@link MergePolicy} used. Note that you can achieve the
+ * same thing by using {@link NoMergePolicy}, however with
+ * {@link NoMergeScheduler} you also ensure that no unnecessary code of any
+ * {@link MergeScheduler} implementation is ever executed. Hence it is
+ * recommended to use both if you want to disable merges from ever happening.
+ */
+public final class NoMergeScheduler extends MergeScheduler {
+
+  /** The single instance of {@link NoMergeScheduler} */
+  public static final MergeScheduler INSTANCE = new NoMergeScheduler();
+
+  private NoMergeScheduler() {
+    // prevent instantiation
+  }
+
+  @Override
+  public void close() {}
+
+  @Override
+  public void merge(IndexWriter writer) throws CorruptIndexException, IOException {}
+
+}

Property changes on: src\java\org\apache\lucene\index\NoMergeScheduler.java
___________________________________________________________________
Added: svn:keywords
   + Date Author Id Revision HeadURL
Added: svn:eol-style
   + native

Index: src/test/org/apache/lucene/index/TestNoMergePolicy.java
===================================================================
--- src/test/org/apache/lucene/index/TestNoMergePolicy.java	(revision 0)
+++ src/test/org/apache/lucene/index/TestNoMergePolicy.java	(revision 0)
@@ -0,0 +1,76 @@
+package org.apache.lucene.index;
+
+/**
+ * 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 static org.junit.Assert.*;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.Arrays;
+
+import org.apache.lucene.util.LuceneTestCaseJ4;
+import org.junit.Test;
+
+public class TestNoMergePolicy extends LuceneTestCaseJ4 {
+
+  @Test
+  public void testNoMergePolicy() throws Exception {
+    MergePolicy mp = NoMergePolicy.NO_COMPOUND_FILES;
+    assertNull(mp.findMerges(null));
+    assertNull(mp.findMergesForOptimize(null, 0, null));
+    assertNull(mp.findMergesToExpungeDeletes(null));
+    assertFalse(mp.useCompoundDocStore(null));
+    assertFalse(mp.useCompoundFile(null, null));
+    mp.close();
+  }
+
+  @Test
+  public void testCompoundFiles() throws Exception {
+    assertFalse(NoMergePolicy.NO_COMPOUND_FILES.useCompoundDocStore(null));
+    assertFalse(NoMergePolicy.NO_COMPOUND_FILES.useCompoundFile(null, null));
+    assertTrue(NoMergePolicy.COMPOUND_FILES.useCompoundDocStore(null));
+    assertTrue(NoMergePolicy.COMPOUND_FILES.useCompoundFile(null, null));
+  }
+
+  @Test
+  public void testFinalSingleton() throws Exception {
+    assertTrue(Modifier.isFinal(NoMergePolicy.class.getModifiers()));
+    Constructor<?>[] ctors = NoMergePolicy.class.getDeclaredConstructors();
+    assertEquals("expected 1 private ctor only: " + Arrays.toString(ctors), 1, ctors.length);
+    assertTrue("that 1 should be private: " + ctors[0], Modifier.isPrivate(ctors[0].getModifiers()));
+  }
+
+  @Test
+  public void testMethodsOverridden() throws Exception {
+    // Ensures that all methods of MergePolicy are overridden. That's important
+    // to ensure that NoMergePolicy overrides everything, so that no unexpected
+    // behavior/error occurs
+    for (Method m : NoMergePolicy.class.getMethods()) {
+      // getDeclaredMethods() returns just those methods that are declared on
+      // NoMergePolicy. getMethods() returns those that are visible in that
+      // context, including ones from Object. So just filter out Object. If in
+      // the future MergePolicy will extend a different class than Object, this
+      // will need to change.
+      if (m.getDeclaringClass() != Object.class) {
+        assertTrue(m + " is not overridden !", m.getDeclaringClass() == NoMergePolicy.class);
+      }
+    }
+  }
+
+}

Property changes on: src\test\org\apache\lucene\index\TestNoMergePolicy.java
___________________________________________________________________
Added: svn:keywords
   + Date Author Id Revision HeadURL
Added: svn:eol-style
   + native

Index: src/test/org/apache/lucene/index/TestNoMergeScheduler.java
===================================================================
--- src/test/org/apache/lucene/index/TestNoMergeScheduler.java	(revision 0)
+++ src/test/org/apache/lucene/index/TestNoMergeScheduler.java	(revision 0)
@@ -0,0 +1,64 @@
+package org.apache.lucene.index;
+
+/**
+ * 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 static org.junit.Assert.*;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.Arrays;
+
+import org.apache.lucene.util.LuceneTestCaseJ4;
+import org.junit.Test;
+
+public class TestNoMergeScheduler extends LuceneTestCaseJ4 {
+
+  @Test
+  public void testNoMergeScheduler() throws Exception {
+    MergeScheduler ms = NoMergeScheduler.INSTANCE;
+    ms.close();
+    ms.merge(null);
+  }
+
+  @Test
+  public void testFinalSingleton() throws Exception {
+    assertTrue(Modifier.isFinal(NoMergeScheduler.class.getModifiers()));
+    Constructor<?>[] ctors = NoMergeScheduler.class.getDeclaredConstructors();
+    assertEquals("expected 1 private ctor only: " + Arrays.toString(ctors), 1, ctors.length);
+    assertTrue("that 1 should be private: " + ctors[0], Modifier.isPrivate(ctors[0].getModifiers()));
+  }
+
+  @Test
+  public void testMethodsOverridden() throws Exception {
+    // Ensures that all methods of MergePolicy are overridden. That's important
+    // to ensure that NoMergePolicy overrides everything, so that no unexpected
+    // behavior/error occurs
+    for (Method m : NoMergeScheduler.class.getMethods()) {
+      // getDeclaredMethods() returns just those methods that are declared on
+      // NoMergeScheduler. getMethods() returns those that are visible in that
+      // context, including ones from Object. So just filter out Object. If in
+      // the future MergeScheduler will extend a different class than Object,
+      // this will need to change.
+      if (m.getDeclaringClass() != Object.class) {
+        assertTrue(m + " is not overridden !", m.getDeclaringClass() == NoMergeScheduler.class);
+      }
+    }
+  }
+
+}

Property changes on: src\test\org\apache\lucene\index\TestNoMergeScheduler.java
___________________________________________________________________
Added: svn:keywords
   + Date Author Id Revision HeadURL
Added: svn:eol-style
   + native