--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/parts/django/tests/modeltests/expressions/tests.py Sat Jan 08 11:20:57 2011 +0530
@@ -0,0 +1,218 @@
+from django.core.exceptions import FieldError
+from django.db.models import F
+from django.test import TestCase
+
+from models import Company, Employee
+
+
+class ExpressionsTests(TestCase):
+ def test_filter(self):
+ Company.objects.create(
+ name="Example Inc.", num_employees=2300, num_chairs=5,
+ ceo=Employee.objects.create(firstname="Joe", lastname="Smith")
+ )
+ Company.objects.create(
+ name="Foobar Ltd.", num_employees=3, num_chairs=4,
+ ceo=Employee.objects.create(firstname="Frank", lastname="Meyer")
+ )
+ Company.objects.create(
+ name="Test GmbH", num_employees=32, num_chairs=1,
+ ceo=Employee.objects.create(firstname="Max", lastname="Mustermann")
+ )
+
+ company_query = Company.objects.values(
+ "name", "num_employees", "num_chairs"
+ ).order_by(
+ "name", "num_employees", "num_chairs"
+ )
+
+ # We can filter for companies where the number of employees is greater
+ # than the number of chairs.
+ self.assertQuerysetEqual(
+ company_query.filter(num_employees__gt=F("num_chairs")), [
+ {
+ "num_chairs": 5,
+ "name": "Example Inc.",
+ "num_employees": 2300,
+ },
+ {
+ "num_chairs": 1,
+ "name": "Test GmbH",
+ "num_employees": 32
+ },
+ ],
+ lambda o: o
+ )
+
+ # We can set one field to have the value of another field
+ # Make sure we have enough chairs
+ company_query.update(num_chairs=F("num_employees"))
+ self.assertQuerysetEqual(
+ company_query, [
+ {
+ "num_chairs": 2300,
+ "name": "Example Inc.",
+ "num_employees": 2300
+ },
+ {
+ "num_chairs": 3,
+ "name": "Foobar Ltd.",
+ "num_employees": 3
+ },
+ {
+ "num_chairs": 32,
+ "name": "Test GmbH",
+ "num_employees": 32
+ }
+ ],
+ lambda o: o
+ )
+
+ # We can perform arithmetic operations in expressions
+ # Make sure we have 2 spare chairs
+ company_query.update(num_chairs=F("num_employees")+2)
+ self.assertQuerysetEqual(
+ company_query, [
+ {
+ 'num_chairs': 2302,
+ 'name': u'Example Inc.',
+ 'num_employees': 2300
+ },
+ {
+ 'num_chairs': 5,
+ 'name': u'Foobar Ltd.',
+ 'num_employees': 3
+ },
+ {
+ 'num_chairs': 34,
+ 'name': u'Test GmbH',
+ 'num_employees': 32
+ }
+ ],
+ lambda o: o,
+ )
+
+ # Law of order of operations is followed
+ company_query.update(
+ num_chairs=F('num_employees') + 2 * F('num_employees')
+ )
+ self.assertQuerysetEqual(
+ company_query, [
+ {
+ 'num_chairs': 6900,
+ 'name': u'Example Inc.',
+ 'num_employees': 2300
+ },
+ {
+ 'num_chairs': 9,
+ 'name': u'Foobar Ltd.',
+ 'num_employees': 3
+ },
+ {
+ 'num_chairs': 96,
+ 'name': u'Test GmbH',
+ 'num_employees': 32
+ }
+ ],
+ lambda o: o,
+ )
+
+ # Law of order of operations can be overridden by parentheses
+ company_query.update(
+ num_chairs=((F('num_employees') + 2) * F('num_employees'))
+ )
+ self.assertQuerysetEqual(
+ company_query, [
+ {
+ 'num_chairs': 5294600,
+ 'name': u'Example Inc.',
+ 'num_employees': 2300
+ },
+ {
+ 'num_chairs': 15,
+ 'name': u'Foobar Ltd.',
+ 'num_employees': 3
+ },
+ {
+ 'num_chairs': 1088,
+ 'name': u'Test GmbH',
+ 'num_employees': 32
+ }
+ ],
+ lambda o: o,
+ )
+
+ # The relation of a foreign key can become copied over to an other
+ # foreign key.
+ self.assertEqual(
+ Company.objects.update(point_of_contact=F('ceo')),
+ 3
+ )
+ self.assertQuerysetEqual(
+ Company.objects.all(), [
+ "Joe Smith",
+ "Frank Meyer",
+ "Max Mustermann",
+ ],
+ lambda c: unicode(c.point_of_contact),
+ )
+
+ c = Company.objects.all()[0]
+ c.point_of_contact = Employee.objects.create(firstname="Guido", lastname="van Rossum")
+ c.save()
+
+ # F Expressions can also span joins
+ self.assertQuerysetEqual(
+ Company.objects.filter(ceo__firstname=F("point_of_contact__firstname")), [
+ "Foobar Ltd.",
+ "Test GmbH",
+ ],
+ lambda c: c.name
+ )
+
+ Company.objects.exclude(
+ ceo__firstname=F("point_of_contact__firstname")
+ ).update(name="foo")
+ self.assertEqual(
+ Company.objects.exclude(
+ ceo__firstname=F('point_of_contact__firstname')
+ ).get().name,
+ "foo",
+ )
+
+ self.assertRaises(FieldError,
+ lambda: Company.objects.exclude(
+ ceo__firstname=F('point_of_contact__firstname')
+ ).update(name=F('point_of_contact__lastname'))
+ )
+
+ # F expressions can be used to update attributes on single objects
+ test_gmbh = Company.objects.get(name="Test GmbH")
+ self.assertEqual(test_gmbh.num_employees, 32)
+ test_gmbh.num_employees = F("num_employees") + 4
+ test_gmbh.save()
+ test_gmbh = Company.objects.get(pk=test_gmbh.pk)
+ self.assertEqual(test_gmbh.num_employees, 36)
+
+ # F expressions cannot be used to update attributes which are foreign
+ # keys, or attributes which involve joins.
+ test_gmbh.point_of_contact = None
+ test_gmbh.save()
+ self.assertTrue(test_gmbh.point_of_contact is None)
+ def test():
+ test_gmbh.point_of_contact = F("ceo")
+ self.assertRaises(ValueError, test)
+
+ test_gmbh.point_of_contact = test_gmbh.ceo
+ test_gmbh.save()
+ test_gmbh.name = F("ceo__last_name")
+ self.assertRaises(FieldError, test_gmbh.save)
+
+ # F expressions cannot be used to update attributes on objects which do
+ # not yet exist in the database
+ acme = Company(
+ name="The Acme Widget Co.", num_employees=12, num_chairs=5,
+ ceo=test_gmbh.ceo
+ )
+ acme.num_employees = F("num_employees") + 16
+ self.assertRaises(TypeError, acme.save)