django/tests/select_related_regress/tests.py

from django.test import TestCase

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


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, str(c.start), str(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, str(c.start), str(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)
        Enrollment.objects.create(std=s, cls=c)

        e_related = Enrollment.objects.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.
        """

        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.assertSequenceEqual(
            Item.objects.select_related("child").order_by("name"),
            [i1, i2],
        )

    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)
        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
        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.assertNotIn("LEFT OUTER", 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.assertIn("LEFT OUTER", str(qs.query))

    def test_regression_19870(self):
        hen = Hen.objects.create(name="Hen")
        Chick.objects.create(name="Chick", mother=hen)

        self.assertEqual(Chick.objects.all()[0].mother.name, "Hen")
        self.assertEqual(Chick.objects.select_related()[0].mother.name, "Hen")

    def test_regression_10733(self):
        a = A.objects.create(name="a", lots_of_text="lots_of_text_a", a_field="a_field")
        b = B.objects.create(name="b", lots_of_text="lots_of_text_b", b_field="b_field")
        c = C.objects.create(
            name="c", lots_of_text="lots_of_text_c", is_published=True, c_a=a, c_b=b
        )
        results = C.objects.only(
            "name",
            "lots_of_text",
            "c_a",
            "c_b",
            "c_b__lots_of_text",
            "c_a__name",
            "c_b__name",
        ).select_related()
        self.assertSequenceEqual(results, [c])
        with self.assertNumQueries(0):
            qs_c = results[0]
            self.assertEqual(qs_c.name, "c")
            self.assertEqual(qs_c.lots_of_text, "lots_of_text_c")
            self.assertEqual(qs_c.c_b.lots_of_text, "lots_of_text_b")
            self.assertEqual(qs_c.c_a.name, "a")
            self.assertEqual(qs_c.c_b.name, "b")

    def test_regression_22508(self):
        building = Building.objects.create(name="101")
        device = Device.objects.create(name="router", building=building)
        Port.objects.create(port_number="1", device=device)

        device = Device.objects.get()
        port = device.port_set.select_related("device__building").get()
        with self.assertNumQueries(0):
            port.device.building