EmptyQuerySet classes can now be merged with normal querysets.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@7765 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/query.py

@@ -218,6 +218,8 @@ class QuerySet(object):
 
     def __and__(self, other):
         self._merge_sanity_check(other)
+        if isinstance(other, EmptyQuerySet):
+            return other._clone()
         combined = self._clone()
         combined.query.combine(other.query, sql.AND)
         return combined
@@ -225,6 +227,8 @@ class QuerySet(object):
     def __or__(self, other):
         self._merge_sanity_check(other)
         combined = self._clone()
+        if isinstance(other, EmptyQuerySet):
+            return combined
         combined.query.combine(other.query, sql.OR)
         return combined
 
@@ -705,6 +709,12 @@ class EmptyQuerySet(QuerySet):
         super(EmptyQuerySet, self).__init__(model, query)
         self._result_cache = []
 
+    def __and__(self, other):
+        return self._clone()
+
+    def __or__(self, other):
+        return other._clone()
+
     def count(self):
         return 0
 

tests/regressiontests/queries/models.py

@@ -781,5 +781,15 @@ Bug #7107 -- this shouldn't create an infinite loop.
 >>> Valid.objects.all()
 []
 
+Empty querysets can be merged with others.
+>>> Note.objects.none() | Note.objects.all()
+[<Note: n1>, <Note: n2>, <Note: n3>]
+>>> Note.objects.all() | Note.objects.none()
+[<Note: n1>, <Note: n2>, <Note: n3>]
+>>> Note.objects.none() & Note.objects.all()
+[]
+>>> Note.objects.all() & Note.objects.none()
+[]
+
 """}