django/tests/expressions/test_queryset_values.py

from django.db.models.aggregates import Sum
from django.db.models.expressions import F
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))