diff --git a/src/mu-msg-iter.cc b/src/mu-msg-iter.cc
index f9f1128a..7860c5b9 100644
--- a/src/mu-msg-iter.cc
+++ b/src/mu-msg-iter.cc
@@ -51,14 +51,14 @@ private:
 
 
 struct _MuMsgIter {
-	_MuMsgIter (Xapian::Enquire &enq, size_t maxnum):
+	_MuMsgIter (Xapian::Enquire &enq, size_t maxnum, gboolean threads):
 		_enq(enq), _msg(0), _threadhash (0) {
 		
 		_matches = _enq.get_mset (0, maxnum);
 
-		if (!_matches.empty()) { 
+		if (threads && !_matches.empty()) { 
 			_matches.fetch();
-			_threadhash = mu_msg_threader_calculate (this);
+			_threadhash = mu_msg_threader_calculate (this, _matches.size());
 			ThreadKeyMaker keymaker(_threadhash);
 			enq.set_sort_by_key (&keymaker, false);
 			_matches = _enq.get_mset (0, maxnum);
@@ -76,7 +76,8 @@ struct _MuMsgIter {
 		if (_msg)
 			mu_msg_unref (_msg);
 
-		g_hash_table_destroy (_threadhash);
+		if (_threadhash)
+			g_hash_table_destroy (_threadhash);
 	}
 	
 	const Xapian::Enquire		_enq;
@@ -90,12 +91,12 @@ struct _MuMsgIter {
 
 
 MuMsgIter*
-mu_msg_iter_new (XapianEnquire *enq, size_t maxnum)
+mu_msg_iter_new (XapianEnquire *enq, size_t maxnum, gboolean threads)
 {
 	g_return_val_if_fail (enq, NULL);
 	
 	try {
-		return new MuMsgIter ((Xapian::Enquire&)*enq, maxnum);
+		return new MuMsgIter ((Xapian::Enquire&)*enq, maxnum, threads);
 		
 	} MU_XAPIAN_CATCH_BLOCK_RETURN(NULL);
 }
diff --git a/src/mu-msg-iter.h b/src/mu-msg-iter.h
index 62032d94..6f93b7a1 100644
--- a/src/mu-msg-iter.h
+++ b/src/mu-msg-iter.h
@@ -44,11 +44,12 @@ typedef struct _MuMsgIter MuMsgIter;
  * @param enq a Xapian::Enquire* cast to XapianEnquire* (because this
  * is C, not C++),providing access to search results
  * @param batchsize how many results to retrieve at once
+ * @param threads whether to calculate threads
  * 
  * @return a new MuMsgIter, or NULL in case of error
  */
 MuMsgIter *mu_msg_iter_new (XapianEnquire *enq,
-			    size_t batchsize) G_GNUC_WARN_UNUSED_RESULT;
+			    size_t batchsize, gboolean threads) G_GNUC_WARN_UNUSED_RESULT;
 
 /**
  * get the next message (which you got from
@@ -117,7 +118,23 @@ MuMsg* mu_msg_iter_get_msg (MuMsgIter *iter, GError **err)
 unsigned int     mu_msg_iter_get_docid         (MuMsgIter *iter);
 
 
+/**
+ * calculate the message threads
+ * 
+ * @param iter a valid MuMsgIter iterator 
+ * 
+ * @return TRUE if it worked, FALSE otherwsie.
+ */
+gboolean mu_msg_iter_calculate_threads (MuMsgIter *iter);
 
+
+/**
+ * get a sortable string describing the path of a thread
+ * 
+ * @param iter a valid MuMsgIter iterator 
+ * 
+ * @return a thread path
+ */
 const char* mu_msg_iter_get_thread_path (MuMsgIter *iter);
 
 /**