django/tests/expressions/test_queryset_values.py

from django.db.models import F, Sum
from django.test import TestCase

from .models import Company, Employee


class ValuesExpressionsTests(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", salary=10),
        )
        Company.objects.create(
            name="Foobar Ltd.",
            num_employees=3,
            num_chairs=4,
            ceo=Employee.objects.create(firstname="Frank", lastname="Meyer", salary=20),
        )
        Company.objects.create(
            name="Test GmbH",
            num_employees=32,
            num_chairs=1,
            ceo=Employee.objects.create(
                firstname="Max", lastname="Mustermann", salary=30
            ),
        )

    def test_values_expression(self):
        self.assertSequenceEqual(
            Company.objects.values(salary=F("ceo__salary")),
            [{"salary": 10}, {"salary": 20}, {"salary": 30}],
        )

    def test_values_expression_group_by(self):
        # values() applies annotate() first, so values selected are grouped by
        # id, not firstname.
        Employee.objects.create(firstname="Joe", lastname="Jones", salary=2)
        joes = Employee.objects.filter(firstname="Joe")
        self.assertSequenceEqual(
            joes.values("firstname", sum_salary=Sum("salary")).order_by("sum_salary"),
            [
                {"firstname": "Joe", "sum_salary": 2},
                {"firstname": "Joe", "sum_salary": 10},
            ],
        )
        self.assertSequenceEqual(
            joes.values("firstname").annotate(sum_salary=Sum("salary")),
            [{"firstname": "Joe", "sum_salary": 12}],
        )

    def test_chained_values_with_expression(self):
        Employee.objects.create(firstname="Joe", lastname="Jones", salary=2)
        joes = Employee.objects.filter(firstname="Joe").values("firstname")
        self.assertSequenceEqual(
            joes.values("firstname", sum_salary=Sum("salary")),
            [{"firstname": "Joe", "sum_salary": 12}],
        )
        self.assertSequenceEqual(
            joes.values(sum_salary=Sum("salary")), [{"sum_salary": 12}]
        )

    def test_values_list_expression(self):
        companies = Company.objects.values_list("name", F("ceo__salary"))
        self.assertSequenceEqual(
            companies, [("Example Inc.", 10), ("Foobar Ltd.", 20), ("Test GmbH", 30)]
        )

    def test_values_list_expression_flat(self):
        companies = Company.objects.values_list(F("ceo__salary"), flat=True)
        self.assertSequenceEqual(companies, (10, 20, 30))