django/tests/expressions/tests.py

from __future__ import unicode_literals

from copy import deepcopy
import datetime

from django.core.exceptions import FieldError
from django.db import connection, transaction, DatabaseError
from django.db.models import F, Value
from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
from django.test.utils import Approximate
from django.utils import six

from .models import Company, Employee, Number, Experiment


class BasicExpressionsTests(TestCase):
    @classmethod
    def setUpTestData(cls):
        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")
        )

    def setUp(self):
        self.company_query = Company.objects.values(
            "name", "num_employees", "num_chairs"
        ).order_by(
            "name", "num_employees", "num_chairs"
        )

    def test_filter_inter_attribute(self):
        # We can filter on attribute relationships on same model obj, e.g.
        # find companies where the number of employees is greater
        # than the number of chairs.
        self.assertQuerysetEqual(
            self.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
        )

    def test_update(self):
        # We can set one field to have the value of another field
        # Make sure we have enough chairs
        self.company_query.update(num_chairs=F("num_employees"))
        self.assertQuerysetEqual(
            self.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
        )

    def test_arithmetic(self):
        # We can perform arithmetic operations in expressions
        # Make sure we have 2 spare chairs
        self.company_query.update(num_chairs=F("num_employees") + 2)
        self.assertQuerysetEqual(
            self.company_query, [
                {
                    'num_chairs': 2302,
                    'name': 'Example Inc.',
                    'num_employees': 2300
                },
                {
                    'num_chairs': 5,
                    'name': 'Foobar Ltd.',
                    'num_employees': 3
                },
                {
                    'num_chairs': 34,
                    'name': 'Test GmbH',
                    'num_employees': 32
                }
            ],
            lambda o: o,
        )

    def test_order_of_operations(self):
        # Law of order of operations is followed
        self. company_query.update(
            num_chairs=F('num_employees') + 2 * F('num_employees')
        )
        self.assertQuerysetEqual(
            self.company_query, [
                {
                    'num_chairs': 6900,
                    'name': 'Example Inc.',
                    'num_employees': 2300
                },
                {
                    'num_chairs': 9,
                    'name': 'Foobar Ltd.',
                    'num_employees': 3
                },
                {
                    'num_chairs': 96,
                    'name': 'Test GmbH',
                    'num_employees': 32
                }
            ],
            lambda o: o,
        )

    def test_parenthesis_priority(self):
        # Law of order of operations can be overridden by parentheses
        self.company_query.update(
            num_chairs=((F('num_employees') + 2) * F('num_employees'))
        )
        self.assertQuerysetEqual(
            self.company_query, [
                {
                    'num_chairs': 5294600,
                    'name': 'Example Inc.',
                    'num_employees': 2300
                },
                {
                    'num_chairs': 15,
                    'name': 'Foobar Ltd.',
                    'num_employees': 3
                },
                {
                    'num_chairs': 1088,
                    'name': 'Test GmbH',
                    'num_employees': 32
                }
            ],
            lambda o: o,
        )

    def test_update_with_fk(self):
        # ForeignKey can become updated with the value of another ForeignKey.
        self.assertEqual(
            Company.objects.update(point_of_contact=F('ceo')),
            3
        )
        self.assertQuerysetEqual(
            Company.objects.all(), [
                "Joe Smith",
                "Frank Meyer",
                "Max Mustermann",
            ],
            lambda c: six.text_type(c.point_of_contact),
            ordered=False
        )

    def test_update_with_none(self):
        Number.objects.create(integer=1, float=1.0)
        Number.objects.create(integer=2)
        Number.objects.filter(float__isnull=False).update(float=Value(None))
        self.assertQuerysetEqual(
            Number.objects.all(), [
                None,
                None,
            ],
            lambda n: n.float,
            ordered=False
        )

    def test_filter_with_join(self):
        # F Expressions can also span joins
        Company.objects.update(point_of_contact=F('ceo'))
        c = Company.objects.all()[0]
        c.point_of_contact = Employee.objects.create(firstname="Guido", lastname="van Rossum")
        c.save()

        self.assertQuerysetEqual(
            Company.objects.filter(ceo__firstname=F("point_of_contact__firstname")), [
                "Foobar Ltd.",
                "Test GmbH",
            ],
            lambda c: c.name,
            ordered=False
        )

        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",
        )

        with transaction.atomic():
            with self.assertRaises(FieldError):
                Company.objects.exclude(
                    ceo__firstname=F('point_of_contact__firstname')
                ).update(name=F('point_of_contact__lastname'))

    def test_object_update(self):
        # 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)

    def test_object_update_fk(self):
        # F expressions cannot be used to update attributes which are foreign
        # keys, or attributes which involve joins.
        test_gmbh = Company.objects.get(name="Test GmbH")

        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)

    def test_object_update_unsaved_objects(self):
        # F expressions cannot be used to update attributes on objects which do
        # not yet exist in the database
        test_gmbh = Company.objects.get(name="Test GmbH")
        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)

    def test_ticket_11722_iexact_lookup(self):
        Employee.objects.create(firstname="John", lastname="Doe")
        Employee.objects.create(firstname="Test", lastname="test")

        queryset = Employee.objects.filter(firstname__iexact=F('lastname'))
        self.assertQuerysetEqual(queryset, ["<Employee: Test test>"])

    @skipIfDBFeature('has_case_insensitive_like')
    def test_ticket_16731_startswith_lookup(self):
        Employee.objects.create(firstname="John", lastname="Doe")
        e2 = Employee.objects.create(firstname="Jack", lastname="Jackson")
        e3 = Employee.objects.create(firstname="Jack", lastname="jackson")
        self.assertQuerysetEqual(
            Employee.objects.filter(lastname__startswith=F('firstname')),
            [e2], lambda x: x)
        self.assertQuerysetEqual(
            Employee.objects.filter(lastname__istartswith=F('firstname')).order_by('pk'),
            [e2, e3], lambda x: x)

    def test_ticket_18375_join_reuse(self):
        # Test that reverse multijoin F() references and the lookup target
        # the same join. Pre #18375 the F() join was generated first, and the
        # lookup couldn't reuse that join.
        qs = Employee.objects.filter(
            company_ceo_set__num_chairs=F('company_ceo_set__num_employees'))
        self.assertEqual(str(qs.query).count('JOIN'), 1)

    def test_ticket_18375_kwarg_ordering(self):
        # The next query was dict-randomization dependent - if the "gte=1"
        # was seen first, then the F() will reuse the join generated by the
        # gte lookup, if F() was seen first, then it generated a join the
        # other lookups could not reuse.
        qs = Employee.objects.filter(
            company_ceo_set__num_chairs=F('company_ceo_set__num_employees'),
            company_ceo_set__num_chairs__gte=1)
        self.assertEqual(str(qs.query).count('JOIN'), 1)

    def test_ticket_18375_kwarg_ordering_2(self):
        # Another similar case for F() than above. Now we have the same join
        # in two filter kwargs, one in the lhs lookup, one in F. Here pre
        # #18375 the amount of joins generated was random if dict
        # randomization was enabled, that is the generated query dependent
        # on which clause was seen first.
        qs = Employee.objects.filter(
            company_ceo_set__num_employees=F('pk'),
            pk=F('company_ceo_set__num_employees')
        )
        self.assertEqual(str(qs.query).count('JOIN'), 1)

    def test_ticket_18375_chained_filters(self):
        # Test that F() expressions do not reuse joins from previous filter.
        qs = Employee.objects.filter(
            company_ceo_set__num_employees=F('pk')
        ).filter(
            company_ceo_set__num_employees=F('company_ceo_set__num_employees')
        )
        self.assertEqual(str(qs.query).count('JOIN'), 2)


class ExpressionsTests(TestCase):

    def test_F_object_deepcopy(self):
        """
        Make sure F objects can be deepcopied (#23492)
        """
        f = F("foo")
        g = deepcopy(f)
        self.assertEqual(f.name, g.name)

    def test_f_reuse(self):
        f = F('id')
        n = Number.objects.create(integer=-1)
        c = Company.objects.create(
            name="Example Inc.", num_employees=2300, num_chairs=5,
            ceo=Employee.objects.create(firstname="Joe", lastname="Smith")
        )
        c_qs = Company.objects.filter(id=f)
        self.assertEqual(c_qs.get(), c)
        # Reuse the same F-object for another queryset
        n_qs = Number.objects.filter(id=f)
        self.assertEqual(n_qs.get(), n)
        # The original query still works correctly
        self.assertEqual(c_qs.get(), c)

    def test_patterns_escape(self):
        """
        Test that special characters (e.g. %, _ and \) stored in database are
        properly escaped when using a pattern lookup with an expression
        refs #16731
        """
        Employee.objects.bulk_create([
            Employee(firstname="%Joh\\nny", lastname="%Joh\\n"),
            Employee(firstname="Johnny", lastname="%John"),
            Employee(firstname="Jean-Claude", lastname="Claud_"),
            Employee(firstname="Jean-Claude", lastname="Claude"),
            Employee(firstname="Jean-Claude", lastname="Claude%"),
            Employee(firstname="Johnny", lastname="Joh\\n"),
            Employee(firstname="Johnny", lastname="John"),
            Employee(firstname="Johnny", lastname="_ohn"),
        ])

        self.assertQuerysetEqual(
            Employee.objects.filter(firstname__contains=F('lastname')),
            ["<Employee: %Joh\\nny %Joh\\n>", "<Employee: Jean-Claude Claude>", "<Employee: Johnny John>"],
            ordered=False)

        self.assertQuerysetEqual(
            Employee.objects.filter(firstname__startswith=F('lastname')),
            ["<Employee: %Joh\\nny %Joh\\n>", "<Employee: Johnny John>"],
            ordered=False)

        self.assertQuerysetEqual(
            Employee.objects.filter(firstname__endswith=F('lastname')),
            ["<Employee: Jean-Claude Claude>"],
            ordered=False)

    def test_insensitive_patterns_escape(self):
        """
        Test that special characters (e.g. %, _ and \) stored in database are
        properly escaped when using a case insensitive pattern lookup with an
        expression -- refs #16731
        """
        Employee.objects.bulk_create([
            Employee(firstname="%Joh\\nny", lastname="%joh\\n"),
            Employee(firstname="Johnny", lastname="%john"),
            Employee(firstname="Jean-Claude", lastname="claud_"),
            Employee(firstname="Jean-Claude", lastname="claude"),
            Employee(firstname="Jean-Claude", lastname="claude%"),
            Employee(firstname="Johnny", lastname="joh\\n"),
            Employee(firstname="Johnny", lastname="john"),
            Employee(firstname="Johnny", lastname="_ohn"),
        ])

        self.assertQuerysetEqual(
            Employee.objects.filter(firstname__icontains=F('lastname')),
            ["<Employee: %Joh\\nny %joh\\n>", "<Employee: Jean-Claude claude>", "<Employee: Johnny john>"],
            ordered=False)

        self.assertQuerysetEqual(
            Employee.objects.filter(firstname__istartswith=F('lastname')),
            ["<Employee: %Joh\\nny %joh\\n>", "<Employee: Johnny john>"],
            ordered=False)

        self.assertQuerysetEqual(
            Employee.objects.filter(firstname__iendswith=F('lastname')),
            ["<Employee: Jean-Claude claude>"],
            ordered=False)


class ExpressionsNumericTests(TestCase):

    def setUp(self):
        Number(integer=-1).save()
        Number(integer=42).save()
        Number(integer=1337).save()
        self.assertEqual(Number.objects.update(float=F('integer')), 3)

    def test_fill_with_value_from_same_object(self):
        """
        We can fill a value in all objects with an other value of the
        same object.
        """
        self.assertQuerysetEqual(
            Number.objects.all(),
            [
                '<Number: -1, -1.000>',
                '<Number: 42, 42.000>',
                '<Number: 1337, 1337.000>'
            ],
            ordered=False
        )

    def test_increment_value(self):
        """
        We can increment a value of all objects in a query set.
        """
        self.assertEqual(
            Number.objects.filter(integer__gt=0)
                  .update(integer=F('integer') + 1),
            2)

        self.assertQuerysetEqual(
            Number.objects.all(),
            [
                '<Number: -1, -1.000>',
                '<Number: 43, 42.000>',
                '<Number: 1338, 1337.000>'
            ],
            ordered=False
        )

    def test_filter_not_equals_other_field(self):
        """
        We can filter for objects, where a value is not equals the value
        of an other field.
        """
        self.assertEqual(
            Number.objects.filter(integer__gt=0)
                  .update(integer=F('integer') + 1),
            2)
        self.assertQuerysetEqual(
            Number.objects.exclude(float=F('integer')),
            [
                '<Number: 43, 42.000>',
                '<Number: 1338, 1337.000>'
            ],
            ordered=False
        )

    def test_complex_expressions(self):
        """
        Complex expressions of different connection types are possible.
        """
        n = Number.objects.create(integer=10, float=123.45)
        self.assertEqual(Number.objects.filter(pk=n.pk).update(
            float=F('integer') + F('float') * 2), 1)

        self.assertEqual(Number.objects.get(pk=n.pk).integer, 10)
        self.assertEqual(Number.objects.get(pk=n.pk).float, Approximate(256.900, places=3))

    def test_incorrect_field_expression(self):
        with six.assertRaisesRegex(self, FieldError, "Cannot resolve keyword u?'nope' into field.*"):
            list(Employee.objects.filter(firstname=F('nope')))


class ExpressionOperatorTests(TestCase):
    def setUp(self):
        self.n = Number.objects.create(integer=42, float=15.5)

    def test_lefthand_addition(self):
        # LH Addition of floats and integers
        Number.objects.filter(pk=self.n.pk).update(
            integer=F('integer') + 15,
            float=F('float') + 42.7
        )

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 57)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(58.200, places=3))

    def test_lefthand_subtraction(self):
        # LH Subtraction of floats and integers
        Number.objects.filter(pk=self.n.pk).update(integer=F('integer') - 15,
                                              float=F('float') - 42.7)

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 27)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(-27.200, places=3))

    def test_lefthand_multiplication(self):
        # Multiplication of floats and integers
        Number.objects.filter(pk=self.n.pk).update(integer=F('integer') * 15,
                                              float=F('float') * 42.7)

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 630)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(661.850, places=3))

    def test_lefthand_division(self):
        # LH Division of floats and integers
        Number.objects.filter(pk=self.n.pk).update(integer=F('integer') / 2,
                                              float=F('float') / 42.7)

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 21)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(0.363, places=3))

    def test_lefthand_modulo(self):
        # LH Modulo arithmetic on integers
        Number.objects.filter(pk=self.n.pk).update(integer=F('integer') % 20)

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 2)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(15.500, places=3))

    def test_lefthand_bitwise_and(self):
        # LH Bitwise ands on integers
        Number.objects.filter(pk=self.n.pk).update(integer=F('integer').bitand(56))

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 40)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(15.500, places=3))

    @skipUnlessDBFeature('supports_bitwise_or')
    def test_lefthand_bitwise_or(self):
        # LH Bitwise or on integers
        Number.objects.filter(pk=self.n.pk).update(integer=F('integer').bitor(48))

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 58)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(15.500, places=3))

    def test_lefthand_power(self):
        # LH Powert arithmetic operation on floats and integers
        Number.objects.filter(pk=self.n.pk).update(integer=F('integer') ** 2,
                                                float=F('float') ** 1.5)
        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 1764)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(61.02, places=2))

    def test_right_hand_addition(self):
        # Right hand operators
        Number.objects.filter(pk=self.n.pk).update(integer=15 + F('integer'),
                                              float=42.7 + F('float'))

        # RH Addition of floats and integers
        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 57)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(58.200, places=3))

    def test_right_hand_subtraction(self):
        Number.objects.filter(pk=self.n.pk).update(integer=15 - F('integer'),
                                              float=42.7 - F('float'))

        # RH Subtraction of floats and integers
        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, -27)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(27.200, places=3))

    def test_right_hand_multiplication(self):
        # RH Multiplication of floats and integers
        Number.objects.filter(pk=self.n.pk).update(integer=15 * F('integer'),
                                              float=42.7 * F('float'))

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 630)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(661.850, places=3))

    def test_right_hand_division(self):
        # RH Division of floats and integers
        Number.objects.filter(pk=self.n.pk).update(integer=640 / F('integer'),
                                              float=42.7 / F('float'))

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 15)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(2.755, places=3))

    def test_right_hand_modulo(self):
        # RH Modulo arithmetic on integers
        Number.objects.filter(pk=self.n.pk).update(integer=69 % F('integer'))

        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 27)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(15.500, places=3))

    def test_righthand_power(self):
        # RH Powert arithmetic operation on floats and integers
        Number.objects.filter(pk=self.n.pk).update(integer=2 ** F('integer'),
                                                float=1.5 ** F('float'))
        self.assertEqual(Number.objects.get(pk=self.n.pk).integer, 4398046511104)
        self.assertEqual(Number.objects.get(pk=self.n.pk).float, Approximate(536.308, places=3))


class FTimeDeltaTests(TestCase):

    def setUp(self):
        sday = datetime.date(2010, 6, 25)
        stime = datetime.datetime(2010, 6, 25, 12, 15, 30, 747000)
        midnight = datetime.time(0)

        delta0 = datetime.timedelta(0)
        delta1 = datetime.timedelta(microseconds=253000)
        delta2 = datetime.timedelta(seconds=44)
        delta3 = datetime.timedelta(hours=21, minutes=8)
        delta4 = datetime.timedelta(days=10)

        # Test data is set so that deltas and delays will be
        # strictly increasing.
        self.deltas = []
        self.delays = []
        self.days_long = []

        # e0: started same day as assigned, zero duration
        end = stime + delta0
        e0 = Experiment.objects.create(name='e0', assigned=sday, start=stime,
            end=end, completed=end.date(), estimated_time=delta0)
        self.deltas.append(delta0)
        self.delays.append(e0.start -
            datetime.datetime.combine(e0.assigned, midnight))
        self.days_long.append(e0.completed - e0.assigned)

        # e1: started one day after assigned, tiny duration, data
        # set so that end time has no fractional seconds, which
        # tests an edge case on sqlite. This Experiment is only
        # included in the test data when the DB supports microsecond
        # precision.
        if connection.features.supports_microsecond_precision:
            delay = datetime.timedelta(1)
            end = stime + delay + delta1
            e1 = Experiment.objects.create(name='e1', assigned=sday,
                start=stime + delay, end=end, completed=end.date(), estimated_time=delta1)
            self.deltas.append(delta1)
            self.delays.append(e1.start -
                datetime.datetime.combine(e1.assigned, midnight))
            self.days_long.append(e1.completed - e1.assigned)

        # e2: started three days after assigned, small duration
        end = stime + delta2
        e2 = Experiment.objects.create(name='e2',
            assigned=sday - datetime.timedelta(3), start=stime, end=end,
            completed=end.date(), estimated_time=datetime.timedelta(hours=1))
        self.deltas.append(delta2)
        self.delays.append(e2.start -
            datetime.datetime.combine(e2.assigned, midnight))
        self.days_long.append(e2.completed - e2.assigned)

        # e3: started four days after assigned, medium duration
        delay = datetime.timedelta(4)
        end = stime + delay + delta3
        e3 = Experiment.objects.create(name='e3',
            assigned=sday, start=stime + delay, end=end, completed=end.date(), estimated_time=delta3)
        self.deltas.append(delta3)
        self.delays.append(e3.start -
            datetime.datetime.combine(e3.assigned, midnight))
        self.days_long.append(e3.completed - e3.assigned)

        # e4: started 10 days after assignment, long duration
        end = stime + delta4
        e4 = Experiment.objects.create(name='e4',
            assigned=sday - datetime.timedelta(10), start=stime, end=end,
            completed=end.date(), estimated_time=delta4 - datetime.timedelta(1))
        self.deltas.append(delta4)
        self.delays.append(e4.start -
            datetime.datetime.combine(e4.assigned, midnight))
        self.days_long.append(e4.completed - e4.assigned)
        self.expnames = [e.name for e in Experiment.objects.all()]

    def test_multiple_query_compilation(self):
        # Ticket #21643
        queryset = Experiment.objects.filter(end__lt=F('start') + datetime.timedelta(hours=1))
        q1 = str(queryset.query)
        q2 = str(queryset.query)
        self.assertEqual(q1, q2)

    def test_query_clone(self):
        # Ticket #21643
        qs = Experiment.objects.filter(end__lt=F('start') + datetime.timedelta(hours=1))
        qs2 = qs.all()
        list(qs)
        list(qs2)

    def test_delta_add(self):
        for i in range(len(self.deltas)):
            delta = self.deltas[i]
            test_set = [e.name for e in
                Experiment.objects.filter(end__lt=F('start') + delta)]
            self.assertEqual(test_set, self.expnames[:i])

            test_set = [e.name for e in
                Experiment.objects.filter(end__lt=delta + F('start'))]
            self.assertEqual(test_set, self.expnames[:i])

            test_set = [e.name for e in
                Experiment.objects.filter(end__lte=F('start') + delta)]
            self.assertEqual(test_set, self.expnames[:i + 1])

    def test_delta_subtract(self):
        for i in range(len(self.deltas)):
            delta = self.deltas[i]
            test_set = [e.name for e in
                Experiment.objects.filter(start__gt=F('end') - delta)]
            self.assertEqual(test_set, self.expnames[:i])

            test_set = [e.name for e in
                Experiment.objects.filter(start__gte=F('end') - delta)]
            self.assertEqual(test_set, self.expnames[:i + 1])

    def test_exclude(self):
        for i in range(len(self.deltas)):
            delta = self.deltas[i]
            test_set = [e.name for e in
                Experiment.objects.exclude(end__lt=F('start') + delta)]
            self.assertEqual(test_set, self.expnames[i:])

            test_set = [e.name for e in
                Experiment.objects.exclude(end__lte=F('start') + delta)]
            self.assertEqual(test_set, self.expnames[i + 1:])

    def test_date_comparison(self):
        for i in range(len(self.days_long)):
            days = self.days_long[i]
            test_set = [e.name for e in
                Experiment.objects.filter(completed__lt=F('assigned') + days)]
            self.assertEqual(test_set, self.expnames[:i])

            test_set = [e.name for e in
                Experiment.objects.filter(completed__lte=F('assigned') + days)]
            self.assertEqual(test_set, self.expnames[:i + 1])

    @skipUnlessDBFeature("supports_mixed_date_datetime_comparisons")
    def test_mixed_comparisons1(self):
        for i in range(len(self.delays)):
            delay = self.delays[i]
            if not connection.features.supports_microsecond_precision:
                delay = datetime.timedelta(delay.days, delay.seconds)
            test_set = [e.name for e in
                Experiment.objects.filter(assigned__gt=F('start') - delay)]
            self.assertEqual(test_set, self.expnames[:i])

            test_set = [e.name for e in
                Experiment.objects.filter(assigned__gte=F('start') - delay)]
            self.assertEqual(test_set, self.expnames[:i + 1])

    def test_mixed_comparisons2(self):
        delays = [datetime.timedelta(delay.days) for delay in self.delays]
        for i in range(len(delays)):
            delay = delays[i]
            test_set = [e.name for e in
                Experiment.objects.filter(start__lt=F('assigned') + delay)]
            self.assertEqual(test_set, self.expnames[:i])

            test_set = [e.name for e in
                Experiment.objects.filter(start__lte=F('assigned') + delay +
                    datetime.timedelta(1))]
            self.assertEqual(test_set, self.expnames[:i + 1])

    def test_delta_update(self):
        for i in range(len(self.deltas)):
            delta = self.deltas[i]
            exps = Experiment.objects.all()
            expected_durations = [e.duration() for e in exps]
            expected_starts = [e.start + delta for e in exps]
            expected_ends = [e.end + delta for e in exps]

            Experiment.objects.update(start=F('start') + delta, end=F('end') + delta)
            exps = Experiment.objects.all()
            new_starts = [e.start for e in exps]
            new_ends = [e.end for e in exps]
            new_durations = [e.duration() for e in exps]
            self.assertEqual(expected_starts, new_starts)
            self.assertEqual(expected_ends, new_ends)
            self.assertEqual(expected_durations, new_durations)

    def test_invalid_operator(self):
        with self.assertRaises(DatabaseError):
            list(Experiment.objects.filter(start=F('start') * datetime.timedelta(0)))

    def test_durationfield_add(self):
        zeros = [e.name for e in
            Experiment.objects.filter(start=F('start') + F('estimated_time'))]
        self.assertEqual(zeros, ['e0'])

        end_less = [e.name for e in
            Experiment.objects.filter(end__lt=F('start') + F('estimated_time'))]
        self.assertEqual(end_less, ['e2'])

        delta_math = [e.name for e in
            Experiment.objects.filter(end__gte=F('start') + F('estimated_time') + datetime.timedelta(hours=1))]
        self.assertEqual(delta_math, ['e4'])

    @skipUnlessDBFeature("has_native_duration_field")
    def test_date_subtraction(self):
        under_estimate = [e.name for e in
            Experiment.objects.filter(estimated_time__gt=F('end') - F('start'))]
        self.assertEqual(under_estimate, ['e2'])

        over_estimate = [e.name for e in
            Experiment.objects.filter(estimated_time__lt=F('end') - F('start'))]
        self.assertEqual(over_estimate, ['e4'])