Index: src/java/org/apache/lucene/index/MultiReader.java
===================================================================
--- src/java/org/apache/lucene/index/MultiReader.java	(revision 816657)
+++ src/java/org/apache/lucene/index/MultiReader.java	(working copy)
@@ -214,8 +214,16 @@
     subReaders[i].getTermFreqVector(docNumber - starts[i], mapper);
   }
 
+  /**
+   * checks whether or not all sub readers are optimized
+   * @return TRUE, iff all sub readers are optimized. FALSE iff any sub readers is not optimized
+   */
   public boolean isOptimized() {
-    return false;
+    ensureOpen();
+    for (IndexReader subReader : subReaders) {
+      if (!subReader.isOptimized()) return false;
+    }
+    return true;
   }
   
   public synchronized int numDocs() {