Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 950226)
+++ lucene/CHANGES.txt	(working copy)
@@ -455,6 +455,11 @@
 * LUCENE-2424: Fix FieldDoc.toString to not just fallback to
   super.toString() (Stephen Green via Mike McCandless)
 
+* LUCENE-2311: Always pass a "fully loaded" (terms index & doc stores)
+  SegmentsReader to IndexWriter's mergedSegmentWarmer (if set), so
+  that warming is free to do whatever it needs to.  (Earwin Burrfoot
+  via Mike McCandless)
+
 New features
 
 * LUCENE-2128: Parallelized fetching document frequencies during weight
Index: lucene/src/test/org/apache/lucene/index/TestIndexWriterReader.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexWriterReader.java	(revision 950226)
+++ lucene/src/test/org/apache/lucene/index/TestIndexWriterReader.java	(working copy)
@@ -32,6 +32,7 @@
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.Query;
+import org.apache.lucene.search.TopDocs;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.MockRAMDirectory;
 import org.apache.lucene.store.AlreadyClosedException;
@@ -840,4 +841,25 @@
     w.close();
   }
 
+  public void testSegmentWarmer() throws Exception {
+    Directory dir = new MockRAMDirectory();
+    IndexWriter w = new IndexWriter(dir, new IndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer())
+                                    .setMaxBufferedDocs(2).setReaderPooling(true));
+    w.setMergedSegmentWarmer(new IndexWriter.IndexReaderWarmer() {
+        public void warm(IndexReader r) throws IOException {
+          final IndexSearcher s = new IndexSearcher(r);
+          final TopDocs hits = s.search(new TermQuery(new Term("foo", "bar")), 10);
+          assertEquals(20, hits.totalHits);
+        }
+      });
+    
+    Document doc = new Document();
+    doc.add(new Field("foo", "bar", Field.Store.YES, Field.Index.NOT_ANALYZED));
+    for(int i=0;i<20;i++) {
+      w.addDocument(doc);
+    }
+    w.waitForMerges();
+    w.close();
+    dir.close();
+  }
 }
Index: lucene/src/test/org/apache/lucene/util/LuceneTestCase.java
===================================================================
--- lucene/src/test/org/apache/lucene/util/LuceneTestCase.java	(revision 950226)
+++ lucene/src/test/org/apache/lucene/util/LuceneTestCase.java	(working copy)
@@ -129,7 +129,18 @@
   @Override
   protected void tearDown() throws Exception {
     BooleanQuery.setMaxClauseCount(savedBoolMaxClauseCount);
+
     try {
+      Thread.setDefaultUncaughtExceptionHandler(savedUncaughtExceptionHandler);
+      if (!uncaughtExceptions.isEmpty()) {
+        System.err.println("The following exceptions were thrown by threads:");
+        for (UncaughtExceptionEntry entry : uncaughtExceptions) {
+          System.err.println("*** Thread: " + entry.thread.getName() + " ***");
+          entry.exception.printStackTrace(System.err);
+        }
+        fail("Some threads threw uncaught exceptions!");
+      }
+
       // this isn't as useful as calling directly from the scope where the 
       // index readers are used, because they could be gc'ed just before
       // tearDown is called.
@@ -145,17 +156,7 @@
     } finally {
       purgeFieldCache(FieldCache.DEFAULT);
     }
-    
-    Thread.setDefaultUncaughtExceptionHandler(savedUncaughtExceptionHandler);
-    if (!uncaughtExceptions.isEmpty()) {
-      System.err.println("The following exceptions were thrown by threads:");
-      for (UncaughtExceptionEntry entry : uncaughtExceptions) {
-        System.err.println("*** Thread: " + entry.thread.getName() + " ***");
-        entry.exception.printStackTrace(System.err);
-      }
-      fail("Some threads throwed uncaught exceptions!");
-    }
-    
+
     super.tearDown();
   }
 
Index: lucene/src/java/org/apache/lucene/index/IndexWriter.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/IndexWriter.java	(revision 950226)
+++ lucene/src/java/org/apache/lucene/index/IndexWriter.java	(working copy)
@@ -4033,7 +4033,21 @@
       // keep deletes (it's costly to open entire reader
       // when we just need deletes)
 
-      final SegmentReader mergedReader = readerPool.get(merge.info, false, BufferedIndexInput.BUFFER_SIZE, -1);
+      final int termsIndexDivisor;
+      final boolean loadDocStores;
+
+      if (poolReaders && mergedSegmentWarmer != null) {
+        // Load terms index & doc stores so the segment
+        // warmer can run searches, load documents/term
+        // vectors
+        termsIndexDivisor = 1;
+        loadDocStores = true;
+      } else {
+        termsIndexDivisor = -1;
+        loadDocStores = false;
+      }
+
+      final SegmentReader mergedReader = readerPool.get(merge.info, loadDocStores, BufferedIndexInput.BUFFER_SIZE, termsIndexDivisor);
       try {
         if (poolReaders && mergedSegmentWarmer != null) {
           mergedSegmentWarmer.warm(mergedReader);