Index: lucene/core/src/test/org/apache/lucene/index/TestIndexWriter.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/index/TestIndexWriter.java	(revision 1496623)
+++ lucene/core/src/test/org/apache/lucene/index/TestIndexWriter.java	(working copy)
@@ -2209,4 +2209,27 @@
       dir.close();
     }
   }
+
+  public void testHasUncommittedChanges() throws IOException {
+    Directory dir = newDirectory();
+    IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig( TEST_VERSION_CURRENT, new MockAnalyzer(random())));
+    assertTrue(writer.hasUncommittedChanges());  // this will be true because a commit will create an empty index
+    Document doc = new Document();
+    doc.add(newTextField("myfield", "a b c", Field.Store.NO));
+    writer.addDocument(doc);
+    assertTrue(writer.hasUncommittedChanges());
+    writer.commit();
+    assertFalse(writer.hasUncommittedChanges());
+    writer.addDocument(doc);
+    assertTrue(writer.hasUncommittedChanges());
+    writer.close();
+
+    writer = new IndexWriter(dir, newIndexWriterConfig( TEST_VERSION_CURRENT, new MockAnalyzer(random())));
+    assertFalse(writer.hasUncommittedChanges());
+    writer.addDocument(doc);
+    assertTrue(writer.hasUncommittedChanges());
+
+    writer.close();
+    dir.close();
+  }
 }
Index: lucene/core/src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(revision 1496623)
+++ lucene/core/src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -214,7 +214,7 @@
   private final Analyzer analyzer;    // how to analyze text
 
   private volatile long changeCount; // increments every time a change is completed
-  private long lastCommitChangeCount; // last changeCount that was committed
+  private volatile long lastCommitChangeCount; // last changeCount that was committed
 
   private List<SegmentInfoPerCommit> rollbackSegments;      // list of segmentInfo we will fallback to if the commit fails
 
@@ -2827,6 +2827,11 @@
     commitInternal();
   }
 
+  /** Returns true if there are changes that have not been committed */
+  public final boolean hasUncommittedChanges() {
+      return changeCount != lastCommitChangeCount;
+  }
+
   private final void commitInternal() throws IOException {
 
     if (infoStream.isEnabled("IW")) {
@@ -2866,8 +2871,8 @@
         if (infoStream.isEnabled("IW")) {
           infoStream.message("IW", "commit: wrote segments file \"" + pendingCommit.getSegmentsFileName() + "\"");
         }
+        segmentInfos.updateGeneration(pendingCommit);
         lastCommitChangeCount = pendingCommitChangeCount;
-        segmentInfos.updateGeneration(pendingCommit);
         rollbackSegments = pendingCommit.createBackupSegmentInfos();
         deleter.checkpoint(pendingCommit, true);
       } finally {