Index: lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/DirectoryTaxonomyWriter.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/DirectoryTaxonomyWriter.java	(revision 1451267)
+++ lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/DirectoryTaxonomyWriter.java	(working copy)
@@ -802,7 +802,7 @@
         te = terms.iterator(te);
         while (te.next() != null) {
           String value = te.term().utf8ToString();
-          CategoryPath cp = new CategoryPath(value, Consts.DEFAULT_DELIMITER);
+          CategoryPath cp = new CategoryPath(value, delimiter);
           final int ordinal = addCategory(cp);
           docs = te.docs(null, docs, DocsEnum.FLAG_NONE);
           ordinalMap.addMapping(docs.nextDoc() + base, ordinal);
Index: lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/Consts.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/Consts.java	(revision 1451267)
+++ lucene/facet/src/java/org/apache/lucene/facet/taxonomy/directory/Consts.java	(working copy)
@@ -36,9 +36,10 @@
    * <P>
    * Originally, we used \uFFFE, officially a "unicode noncharacter" (invalid
    * unicode character) for this purpose. Recently, we switched to the
-   * "private-use" character \uF749.
+   * "private-use" character \uF749.  Even more recently, we
+   * switched to \U001F (INFORMATION_SEPARATOR).
    */
   //static final char DEFAULT_DELIMITER = '\uFFFE';
-  static final char DEFAULT_DELIMITER = '\uF749';
-  
+  //static final char DEFAULT_DELIMITER = '\uF749';
+  static final char DEFAULT_DELIMITER = '\u001F';
 }
Index: lucene/facet/src/java/org/apache/lucene/facet/params/FacetIndexingParams.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/params/FacetIndexingParams.java	(revision 1451267)
+++ lucene/facet/src/java/org/apache/lucene/facet/params/FacetIndexingParams.java	(working copy)
@@ -58,7 +58,7 @@
    * make sure that you return a character that's not found in any path
    * component.
    */
-  public static final char DEFAULT_FACET_DELIM_CHAR = '\uF749';
+  public static final char DEFAULT_FACET_DELIM_CHAR = '\u001F';
   
   private final int partitionSize = Integer.MAX_VALUE;
 
Index: lucene/CHANGES.txt
===================================================================
--- lucene/CHANGES.txt	(revision 1451267)
+++ lucene/CHANGES.txt	(working copy)
@@ -79,6 +79,11 @@
 * LUCENE-4748: A FacetRequest on a non-existent field now returns an
   empty FacetResult instead of skipping it.  (Shai Erera, Mike McCandless)
 
+* LUCENE-4806: The default category delimiter character was changed
+  from U+F749 to U+001F, since the latter uses 1 byte vs 3 bytes for
+  the former.  Existing facet indices must be reindexed.  (Robert
+  Muir, Shai Erera, Mike McCandless)
+
 Optimizations
 
 * LUCENE-4687: BloomFilterPostingsFormat now lazily initializes delegate