Ticket #3283: empty_queryset.patch

db/models/manager.py

@@ -1 @@
-from django.db.models.query import QuerySet
+from django.db.models.query import QuerySet, EmptyQuerySet
 from django.dispatch import dispatcher
 from django.db.models import signals
 from django.db.models.fields import FieldDoesNotExist
@@ -41 +41 @@
     #######################
     # PROXIES TO QUERYSET #
     #######################
+    
+    def get_empty_query_set(self):
+        return EmptyQuerySet(self.model)
 
     def get_query_set(self):
         """Returns a new QuerySet object.  Subclasses can override this method
         to easily customise the behaviour of the Manager.
         """
         return QuerySet(self.model)
+    
+    def none(self):
+        return self.get_empty_query_set()
 
     def all(self):
         return self.get_query_set()

db/models/query.py

@@ -562 +562 @@
         c._kind = self._kind
         c._order = self._order
         return c
+    
+class EmptyQuerySet(QuerySet):
+    def __init__(self, model=None):
+        super(EmptyQuerySet,self).__init__(model)
+        self._result_cache = []
+        
+    def iterator(self):
+        raise StopIteration
+        
+    def count(self):
+        return 0
+        
+    def delete(self):
+        pass
 
+    def _clone(self, klass=None, **kwargs):
+        c = super(EmptyQuerySet, self)._clone(klass, **kwargs)
+        c._result_cache = []
+        return c
+
 class QOperator(object):
     "Base class for QAnd and QOr"
     def __init__(self, *args):