added meta support for indexes ensured at call-time

mongoengine/base.py

@@ -154,8 +154,12 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
             'allow_inheritance': True,
             'max_documents': None,
             'max_size': None,
+            'indexes': [] # indexes to be ensured at runtime
         }
+
+        # Apply document-defined meta options
         meta.update(attrs.get('meta', {}))
+        
         # Only simple classes - direct subclasses of Document - may set
         # allow_inheritance to False
         if not simple_class and not meta['allow_inheritance']:

mongoengine/queryset.py

@@ -30,18 +30,32 @@ class QuerySet(object):
         """
         if isinstance(key_or_list, basestring):
             # single-field indexes needn't specify a direction
-            if key_or_list.startswith("-"):
+            if key_or_list.startswith("-") or key_or_list.startswith("+"):
                 key_or_list = key_or_list[1:]
             self._collection.ensure_index(key_or_list)
         elif isinstance(key_or_list, (list, tuple)):
-            print key_or_list
-            self._collection.ensure_index(key_or_list)
+            index_list = []
+            for key in key_or_list:
+                if key.startswith("-"):
+                    index_list.append((key[1:], pymongo.DESCENDING))
+                else:
+                    if key.startswith("+"):
+                        key = key[1:]
+                    index_list.append((key, pymongo.ASCENDING))
+            self._collection.ensure_index(index_list)
         return self
 
     def __call__(self, **query):
         """Filter the selected documents by calling the 
         :class:`~mongoengine.QuerySet` with a query.
         """
+        
+        # ensure document-defined indexes are created
+        if self._document._meta['indexes']:
+            for key_or_list in self._document._meta['indexes']:
+                # print "key", key_or_list
+                self.ensure_index(key_or_list)
+        
         query = QuerySet._transform_query(_doc_cls=self._document, **query)
         self._query.update(query)
         return self