Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 1213386)
+++ lucene/CHANGES.txt	(working copy)
@@ -612,6 +612,10 @@
   (Mike McCandless, Uwe Schindler, Robert Muir, Chris Male, Yonik Seeley,
   Jason Rutherglen, Paul Elschot)
 
+* LUCENE-3638: Added sugar methods to IndexReader and IndexSearcher to
+  load only certain fields when loading a document.  (Peter Chang via
+  Mike McCandless)
+
 Optimizations
 
 * LUCENE-2588: Don't store unnecessary suffixes when writing the terms
Index: lucene/src/test/org/apache/lucene/index/TestIndexReader.java
===================================================================
--- lucene/src/test/org/apache/lucene/index/TestIndexReader.java	(revision 1213386)
+++ lucene/src/test/org/apache/lucene/index/TestIndexReader.java	(working copy)
@@ -25,10 +25,9 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Map;
-import java.util.HashMap;
 import java.util.Random;
-import org.junit.Assume;
+import java.util.Set;
+
 import org.apache.lucene.analysis.MockAnalyzer;
 import org.apache.lucene.document.BinaryField;
 import org.apache.lucene.document.Document;
@@ -37,20 +36,18 @@
 import org.apache.lucene.document.StringField;
 import org.apache.lucene.document.TextField;
 import org.apache.lucene.index.IndexReader.FieldOption;
+import org.apache.lucene.index.IndexWriterConfig.OpenMode;
 import org.apache.lucene.index.codecs.lucene40.Lucene40PostingsFormat;
-import org.apache.lucene.index.IndexWriterConfig.OpenMode;
 import org.apache.lucene.search.DocIdSetIterator;
 import org.apache.lucene.search.FieldCache;
-import org.apache.lucene.search.similarities.DefaultSimilarity;
-import org.apache.lucene.store.AlreadyClosedException;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.LockObtainFailedException;
 import org.apache.lucene.store.NoSuchDirectoryException;
-import org.apache.lucene.store.LockReleaseFailedException;
+import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util._TestUtil;
-import org.apache.lucene.util.BytesRef;
-import org.apache.lucene.util.Bits;
+import org.junit.Assume;
 
 public class TestIndexReader extends LuceneTestCase {
         
@@ -1066,4 +1063,23 @@
       }
     }
   }
+
+  public void testLoadCertainFields() throws Exception {
+    Directory dir = newDirectory();
+    RandomIndexWriter writer = new RandomIndexWriter(random, dir);
+    Document doc = new Document();
+    doc.add(newField("field1", "foobar", StringField.TYPE_STORED));
+    doc.add(newField("field2", "foobaz", StringField.TYPE_STORED));
+    writer.addDocument(doc);
+    IndexReader r = writer.getReader();
+    writer.close();
+    Set<String> fieldsToLoad = new HashSet<String>();
+    assertEquals(0, r.document(0, fieldsToLoad).getFields().size());
+    fieldsToLoad.add("field1");
+    Document doc2 = r.document(0, fieldsToLoad);
+    assertEquals(1, doc2.getFields().size());
+    assertEquals("foobar", doc2.get("field1"));
+    r.close();
+    dir.close();
+  }
 }
Index: lucene/src/java/org/apache/lucene/search/IndexSearcher.java
===================================================================
--- lucene/src/java/org/apache/lucene/search/IndexSearcher.java	(revision 1213386)
+++ lucene/src/java/org/apache/lucene/search/IndexSearcher.java	(working copy)
@@ -17,10 +17,10 @@
  * limitations under the License.
  */
 
-import java.io.Closeable;
 import java.io.IOException;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
+import java.util.Set;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CompletionService;
 import java.util.concurrent.ExecutionException;
@@ -176,16 +176,21 @@
     return reader;
   }
 
-  /* Sugar for <code>.getIndexReader().document(docID)</code> */
+  /** Sugar for <code>.getIndexReader().document(docID)</code> */
   public Document doc(int docID) throws CorruptIndexException, IOException {
     return reader.document(docID);
   }
 
-  /* Sugar for <code>.getIndexReader().document(docID, fieldVisitor)</code> */
+  /** Sugar for <code>.getIndexReader().document(docID, fieldVisitor)</code> */
   public void doc(int docID, StoredFieldVisitor fieldVisitor) throws CorruptIndexException, IOException {
     reader.document(docID, fieldVisitor);
   }
 
+  /** Sugar for <code>.getIndexReader().document(docID, fieldsToLoad)</code> */
+  public final Document document(int docID, Set<String> fieldsToLoad) throws CorruptIndexException, IOException {
+    return reader.document(docID, fieldsToLoad);
+  }
+
   /** Expert: Set the SimilarityProvider implementation used by this Searcher.
    *
    */
Index: lucene/src/java/org/apache/lucene/index/IndexReader.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/IndexReader.java	(revision 1213386)
+++ lucene/src/java/org/apache/lucene/index/IndexReader.java	(working copy)
@@ -24,6 +24,7 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import org.apache.lucene.document.Document;
@@ -737,6 +738,17 @@
     return visitor.getDocument();
   }
 
+  /**
+   * Like {@link document(int)} but only loads the specified
+   * fields.  Note that this is simply sugar for {@link
+   * DocumentStoredFieldVisitor#DocumentStoredFieldVisitor(Set<String>)}.
+   */
+  public final Document document(int docID, Set<String> fieldsToLoad) throws CorruptIndexException, IOException {
+    final DocumentStoredFieldVisitor visitor = new DocumentStoredFieldVisitor(fieldsToLoad);
+    document(docID, visitor);
+    return visitor.getDocument();
+  }
+
   /** Returns true if any documents have been deleted */
   public abstract boolean hasDeletions();