Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 1392448)
+++ lucene/CHANGES.txt	(working copy)
@@ -216,6 +216,11 @@
 * LUCENE-4401: Fix bug where DisjunctionSumScorer would sometimes call score()
   on a subscorer that had already returned NO_MORE_DOCS.  (Liu Chao, Robert Muir)
 
+* LUCENE-4455: Fix bug in SegmentInfoPerCommit.sizeInBytes() that was
+  returning 2X the true size, inefficiently.  Also fixed bug in
+  CheckIndex that would report no deletions when a segment has
+  deletions, and vice/versa.  (Uwe Schindler, Robert Muir, Mike McCandless)
+
 Optimizations
 
 * LUCENE-4322: Decrease lucene-core JAR size. The core JAR size had increased a
Index: lucene/core/src/test/org/apache/lucene/index/TestRollingUpdates.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/index/TestRollingUpdates.java	(revision 1392448)
+++ lucene/core/src/test/org/apache/lucene/index/TestRollingUpdates.java	(working copy)
@@ -133,6 +133,21 @@
     docs.close();
     
     _TestUtil.checkIndex(dir);
+
+    // LUCENE-4455:
+    SegmentInfos infos = new SegmentInfos();
+    infos.read(dir);
+    long totalBytes = 0;
+    for(SegmentInfoPerCommit sipc : infos) {
+      totalBytes += sipc.sizeInBytes();
+    }
+    long totalBytes2 = 0;
+    for(String fileName : dir.listAll()) {
+      if (!fileName.startsWith(IndexFileNames.SEGMENTS)) {
+        totalBytes2 += dir.fileLength(fileName);
+      }
+    }
+    assertEquals(totalBytes2, totalBytes);
     dir.close();
   }
   
Index: lucene/core/src/test/org/apache/lucene/index/TestIndexWriterDelete.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/index/TestIndexWriterDelete.java	(revision 1392448)
+++ lucene/core/src/test/org/apache/lucene/index/TestIndexWriterDelete.java	(working copy)
@@ -17,7 +17,9 @@
  * limitations under the License.
  */
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.io.PrintStream;
 import java.io.Reader;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -1071,4 +1073,47 @@
     w.close();
     dir.close();
   }
+
+  // LUCENE-4455
+  public void testDeletesCheckIndexOutput() throws Exception {
+    Directory dir = newDirectory();
+    IndexWriterConfig iwc = new IndexWriterConfig(TEST_VERSION_CURRENT, new MockAnalyzer(random()));
+    iwc.setMaxBufferedDocs(2);
+    IndexWriter w = new IndexWriter(dir, iwc);
+    Document doc = new Document();
+    doc.add(newField("field", "0", StringField.TYPE_NOT_STORED));
+    w.addDocument(doc);
+
+    doc = new Document();
+    doc.add(newField("field", "1", StringField.TYPE_NOT_STORED));
+    w.addDocument(doc);
+    w.commit();
+    assertEquals(1, w.getSegmentCount());
+
+    w.deleteDocuments(new Term("field", "0"));
+    w.commit();
+    assertEquals(1, w.getSegmentCount());
+    w.close();
+
+    ByteArrayOutputStream bos = new ByteArrayOutputStream(1024);
+    CheckIndex checker = new CheckIndex(dir);
+    checker.setInfoStream(new PrintStream(bos, false, "UTF-8"), false);
+    CheckIndex.Status indexStatus = checker.checkIndex(null);
+    assertTrue(indexStatus.clean);
+    String s = bos.toString("UTF-8");
+
+    // Segment should have deletions:
+    assertTrue(s.contains("has deletions"));
+    w = new IndexWriter(dir, iwc);
+    w.forceMerge(1);
+    w.close();
+
+    bos = new ByteArrayOutputStream(1024);
+    checker.setInfoStream(new PrintStream(bos, false, "UTF-8"), false);
+    indexStatus = checker.checkIndex(null);
+    assertTrue(indexStatus.clean);
+    s = bos.toString("UTF-8");
+    assertFalse(s.contains("has deletions"));
+    dir.close();
+  }
 }
Index: lucene/core/src/java/org/apache/lucene/index/CheckIndex.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/CheckIndex.java	(revision 1392448)
+++ lucene/core/src/java/org/apache/lucene/index/CheckIndex.java	(working copy)
@@ -520,7 +520,7 @@
 
         // TODO: we could append the info attributes() to the msg?
 
-        if (info.hasDeletions()) {
+        if (!info.hasDeletions()) {
           msg("    no deletions");
           segInfoStat.hasDeletions = false;
         }
Index: lucene/core/src/java/org/apache/lucene/index/SegmentInfoPerCommit.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/index/SegmentInfoPerCommit.java	(revision 1392448)
+++ lucene/core/src/java/org/apache/lucene/index/SegmentInfoPerCommit.java	(working copy)
@@ -67,9 +67,7 @@
    *  segment. */
   public long sizeInBytes() throws IOException {
     if (sizeInBytes == -1) {
-      final Collection<String> files = new HashSet<String>();
-      info.getCodec().liveDocsFormat().files(this, files);
-      long sum = info.sizeInBytes();
+      long sum = 0;
       for (final String fileName : files()) {
         sum += info.dir.fileLength(fileName);
       }