Ticket #17186: 17186-4.patch

django/db/models/expressions.py

@@ -70 +70 @@
     def __or__(self, other):
         return self._combine(other, self.OR, False)
 
+    def __invert__(self):
+        return NotNode([self])
+
     def __radd__(self, other):
         return self._combine(other, self.ADD, True)
 
@@ -113 +116 @@
     def evaluate(self, evaluator, qn, connection):
         return evaluator.evaluate_leaf(self, qn, connection)
 
+class NotNode(ExpressionNode):
+    """
+    Node that represents a negation.
+    """
+    def __init__(self, children=None):
+        super(NotNode, self).__init__(children, None, True)
+
+    def evaluate(self, evaluator, qn, connection):
+        sql, params = evaluator.evaluate_node(self, qn, connection)
+        return ("NOT %s" % sql, params)
+
 class DateModifierNode(ExpressionNode):
     """
     Node that implements the following syntax:

docs/topics/db/queries.txt

@@ -594 +594 @@
     >>> from datetime import timedelta
     >>> Entry.objects.filter(mod_date__gt=F('pub_date') + timedelta(days=3))
 
+.. versionadded:: 1.4
+
+Additionally, ``F()`` objects can be negated using the ``~`` operator.
+Note that for ``NULL`` values, this performs no changes::
+
+    >>> class A(Model):
+    ...    f = NullBooleanField()
+    ...
+    >>> A.objects.create()
+    <A: A object>
+    >>> for m in A.objects.all():
+    ...     m.f = not m.f; m.save()  # all NULL values are now True 
+    ...
+    >>> A.objects.values('f')
+    [{'f': True}] 
+    >>> A.objects.all().delete()
+    >>> A.objects.create()
+    <A: A object>
+    >>> A.objects.update(f=~F('f')) # this leaves NULL values unchanged as NOT NULL is NULL
+    1
+    >>> A.objects.values('f')
+    [{'f': None}]
+
 The pk lookup shortcut
 ----------------------
 

tests/modeltests/expressions/models.py

@@ -8 +8 @@
 class Employee(models.Model):
     firstname = models.CharField(max_length=50)
     lastname = models.CharField(max_length=50)
+    is_active = models.BooleanField(default=False)
 
     def __unicode__(self):
         return u'%s %s' % (self.firstname, self.lastname)
@@ -26 +27 @@
 
     def __unicode__(self):
         return self.name
+
+

tests/modeltests/expressions/tests.py

@@ -22 +22 @@
             ceo=Employee.objects.create(firstname="Max", lastname="Mustermann")
         )
 
+        # mark active employees when their companies have num_chairs greater than 3
+        employee_qs = Employee.objects.filter(is_active=False)
+        self.assertEqual(employee_qs.count(), 3)
+
+        Employee.objects.filter(company_ceo_set__num_chairs__gte=3)\
+            .update(is_active=~F("is_active"))
+
+        employee_qs = Employee.objects.filter(is_active=False)
+        self.assertEqual(employee_qs.count(), 1)
+
+        employee_qs = Employee.objects.filter(is_active=~(~F('is_active')))
+        self.assertEqual(employee_qs.count(), Employee.objects.count())
+
         company_query = Company.objects.values(
             "name", "num_employees", "num_chairs"
         ).order_by(