Index: src/java/org/apache/lucene/index/FieldsReader.java
===================================================================
--- src/java/org/apache/lucene/index/FieldsReader.java	(revision 962932)
+++ src/java/org/apache/lucene/index/FieldsReader.java	(working copy)
@@ -218,8 +218,8 @@
     long position = indexStream.readLong();
     fieldsStream.seek(position);
 
-    Document doc = new Document();
-    int numFields = fieldsStream.readVInt();
+    final int numFields = fieldsStream.readVInt();
+    final Document doc = new Document((fieldSelector == null && numFields > 10) ? numFields : 10);
     for (int i = 0; i < numFields; i++) {
       int fieldNumber = fieldsStream.readVInt();
       FieldInfo fi = fieldInfos.fieldInfo(fieldNumber);
Index: src/java/org/apache/lucene/document/Document.java
===================================================================
--- src/java/org/apache/lucene/document/Document.java	(revision 962932)
+++ src/java/org/apache/lucene/document/Document.java	(working copy)
@@ -18,6 +18,7 @@
  */
 
 import java.util.*;             // for javadoc
+
 import org.apache.lucene.search.ScoreDoc; // for javadoc
 import org.apache.lucene.search.Searcher;  // for javadoc
 import org.apache.lucene.index.IndexReader;  // for javadoc
@@ -37,13 +38,26 @@
  */
 
 public final class Document implements java.io.Serializable {
-  List<Fieldable> fields = new ArrayList<Fieldable>();
+  final List<Fieldable> fields;
   private float boost = 1.0f;
 
   /** Constructs a new document with no fields. */
-  public Document() {}
+  public Document() {
+    this(new ArrayList<Fieldable>());
+  }
+  
+  /** Construct a Document with an initial capacity for fields
+   * @param initialCapacity   initial number of fields in the internal List */
+  public Document(final int initialCapacity) {
+    this(new ArrayList<Fieldable>(initialCapacity));
+  }
+  
+  /** Construct a Document with a List of Fieldables
+   * @param fields  a List of Fielables to use. NOT COPIED, so be careful */
+  public Document(final List<Fieldable> fields) {
+    this.fields = fields;
+  }
 
-
   /** Sets a boost factor for hits on any field of this document.  This value
    * will be multiplied into the score of all hits on this document.
    *