From 9e23c3c5d9d796540356906399365c651e07f084 Mon Sep 17 00:00:00 2001
From: Malcolm Tredinnick <malcolm.tredinnick@gmail.com>
Date: Thu, 26 Jun 2008 11:42:12 +0000
Subject: [PATCH] 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               | 10 ++++++++++
 tests/regressiontests/queries/models.py | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/django/db/models/query.py b/django/db/models/query.py
index eff4c57a7c..fef71640b6 100644
--- a/django/db/models/query.py
+++ b/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
 
diff --git a/tests/regressiontests/queries/models.py b/tests/regressiontests/queries/models.py
index cfbaf773d6..c02ad73998 100644
--- a/tests/regressiontests/queries/models.py
+++ b/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()
+[]
+
 """}