django/tests/regressiontests/select_related_regress/tests.py

from __future__ import absolute_import, unicode_literals

from django.test import TestCase
from django.utils import six

from .models import (Building, Child, Device, Port, Item, Country, Connection,
    ClientStatus, State, Client, SpecialClient, TUser, Person, Student,
    Organizer, Class, Enrollment)


class SelectRelatedRegressTests(TestCase):

    def test_regression_7110(self):
        """
        Regression test for bug #7110.

        When using select_related(), we must query the
        Device and Building tables using two different aliases (each) in order to
        differentiate the start and end Connection fields. The net result is that
        both the "connections = ..." queries here should give the same results
        without pulling in more than the absolute minimum number of tables
        (history has shown that it's easy to make a mistake in the implementation
        and include some unnecessary bonus joins).
        """

        b=Building.objects.create(name='101')
        dev1=Device.objects.create(name="router", building=b)
        dev2=Device.objects.create(name="switch", building=b)
        dev3=Device.objects.create(name="server", building=b)
        port1=Port.objects.create(port_number='4',device=dev1)
        port2=Port.objects.create(port_number='7',device=dev2)
        port3=Port.objects.create(port_number='1',device=dev3)
        c1=Connection.objects.create(start=port1, end=port2)
        c2=Connection.objects.create(start=port2, end=port3)

        connections=Connection.objects.filter(start__device__building=b, end__device__building=b).order_by('id')
        self.assertEqual([(c.id, six.text_type(c.start), six.text_type(c.end)) for c in connections],
            [(c1.id, 'router/4', 'switch/7'), (c2.id, 'switch/7', 'server/1')])

        connections=Connection.objects.filter(start__device__building=b, end__device__building=b).select_related().order_by('id')
        self.assertEqual([(c.id, six.text_type(c.start), six.text_type(c.end)) for c in connections],
            [(c1.id, 'router/4', 'switch/7'), (c2.id, 'switch/7', 'server/1')])

        # This final query should only have seven tables (port, device and building
        # twice each, plus connection once). Thus, 6 joins plus the FROM table.
        self.assertEqual(str(connections.query).count(" JOIN "), 6)


    def test_regression_8106(self):
        """
        Regression test for bug #8106.

        Same sort of problem as the previous test, but this time there are
        more extra tables to pull in as part of the select_related() and some
        of them could potentially clash (so need to be kept separate).
        """

        us = TUser.objects.create(name="std")
        usp = Person.objects.create(user=us)
        uo = TUser.objects.create(name="org")
        uop = Person.objects.create(user=uo)
        s = Student.objects.create(person = usp)
        o = Organizer.objects.create(person = uop)
        c = Class.objects.create(org=o)
        e = Enrollment.objects.create(std=s, cls=c)

        e_related = Enrollment.objects.all().select_related()[0]
        self.assertEqual(e_related.std.person.user.name, "std")
        self.assertEqual(e_related.cls.org.person.user.name, "org")

    def test_regression_8036(self):
        """
        Regression test for bug #8036

        the first related model in the tests below
        ("state") is empty and we try to select the more remotely related
        state__country. The regression here was not skipping the empty column results
        for country before getting status.
        """

        australia = Country.objects.create(name='Australia')
        active = ClientStatus.objects.create(name='active')
        client = Client.objects.create(name='client', status=active)

        self.assertEqual(client.status, active)
        self.assertEqual(Client.objects.select_related()[0].status, active)
        self.assertEqual(Client.objects.select_related('state')[0].status, active)
        self.assertEqual(Client.objects.select_related('state', 'status')[0].status, active)
        self.assertEqual(Client.objects.select_related('state__country')[0].status, active)
        self.assertEqual(Client.objects.select_related('state__country', 'status')[0].status, active)
        self.assertEqual(Client.objects.select_related('status')[0].status, active)

    def test_multi_table_inheritance(self):
        """ Exercising select_related() with multi-table model inheritance. """
        c1 = Child.objects.create(name="child1", value=42)
        i1 = Item.objects.create(name="item1", child=c1)
        i2 = Item.objects.create(name="item2")

        self.assertQuerysetEqual(
                Item.objects.select_related("child").order_by("name"),
                ["<Item: item1>", "<Item: item2>"]
        )

    def test_regression_12851(self):
        """
        Regression for #12851

        Deferred fields are used correctly if you select_related a subset
        of fields.
        """
        australia = Country.objects.create(name='Australia')
        active = ClientStatus.objects.create(name='active')

        wa = State.objects.create(name="Western Australia", country=australia)
        c1 = Client.objects.create(name='Brian Burke', state=wa, status=active)
        burke = Client.objects.select_related('state').defer('state__name').get(name='Brian Burke')

        self.assertEqual(burke.name, 'Brian Burke')
        self.assertEqual(burke.state.name, 'Western Australia')

        # Still works if we're dealing with an inherited class
        sc1 = SpecialClient.objects.create(name='Troy Buswell', state=wa, status=active, value=42)
        troy = SpecialClient.objects.select_related('state').defer('state__name').get(name='Troy Buswell')

        self.assertEqual(troy.name, 'Troy Buswell')
        self.assertEqual(troy.value, 42)
        self.assertEqual(troy.state.name, 'Western Australia')

        # Still works if we defer an attribute on the inherited class
        troy = SpecialClient.objects.select_related('state').defer('value', 'state__name').get(name='Troy Buswell')

        self.assertEqual(troy.name, 'Troy Buswell')
        self.assertEqual(troy.value, 42)
        self.assertEqual(troy.state.name, 'Western Australia')

        # Also works if you use only, rather than defer
        troy = SpecialClient.objects.select_related('state').only('name', 'state').get(name='Troy Buswell')

        self.assertEqual(troy.name, 'Troy Buswell')
        self.assertEqual(troy.value, 42)
        self.assertEqual(troy.state.name, 'Western Australia')

    def test_null_join_promotion(self):
        australia = Country.objects.create(name='Australia')
        active = ClientStatus.objects.create(name='active')

        wa = State.objects.create(name="Western Australia", country=australia)
        bob = Client.objects.create(name='Bob', status=active)
        jack = Client.objects.create(name='Jack', status=active, state=wa)
        qs = Client.objects.filter(state=wa).select_related('state')
        with self.assertNumQueries(1):
            self.assertEqual(list(qs), [jack])
            self.assertEqual(qs[0].state, wa)
            # The select_related join wasn't promoted as there was already an
            # existing (even if trimmed) inner join to state.
            self.assertFalse('LEFT OUTER' in str(qs.query))
        qs = Client.objects.select_related('state').order_by('name')
        with self.assertNumQueries(1):
            self.assertEqual(list(qs), [bob, jack])
            self.assertIs(qs[0].state, None)
            self.assertEqual(qs[1].state, wa)
            # The select_related join was promoted as there is already an
            # existing join.
            self.assertTrue('LEFT OUTER' in str(qs.query))