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291 lines
9.8 KiB
Python
291 lines
9.8 KiB
Python
from __future__ import absolute_import, unicode_literals
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from django.core.exceptions import FieldError
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from django.db.models import F
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from django.test import TestCase
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from django.utils import six
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from .models import Company, Employee
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class ExpressionsTests(TestCase):
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def test_filter(self):
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Company.objects.create(
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name="Example Inc.", num_employees=2300, num_chairs=5, is_large=False,
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ceo=Employee.objects.create(firstname="Joe", lastname="Smith")
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)
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Company.objects.create(
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name="Foobar Ltd.", num_employees=3, num_chairs=4, is_large=False,
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ceo=Employee.objects.create(firstname="Frank", lastname="Meyer")
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)
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Company.objects.create(
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name="Test GmbH", num_employees=32, num_chairs=1, is_large=False,
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ceo=Employee.objects.create(firstname="Max", lastname="Mustermann")
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)
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company_query = Company.objects.values(
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"name", "num_employees", "num_chairs", "is_large"
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).order_by(
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"name", "num_employees", "num_chairs", "is_large"
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)
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# We can filter for companies where the number of employees is greater
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# than the number of chairs.
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self.assertQuerysetEqual(
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company_query.filter(num_employees__gt=F("num_chairs")), [
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{
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"num_chairs": 5,
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"name": "Example Inc.",
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"num_employees": 2300,
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"is_large": False
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},
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{
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"num_chairs": 1,
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"name": "Test GmbH",
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"num_employees": 32,
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"is_large": False
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},
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],
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lambda o: o
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)
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# We can set one field to have the value of another field
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# Make sure we have enough chairs
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company_query.update(num_chairs=F("num_employees"))
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self.assertQuerysetEqual(
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company_query, [
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{
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"num_chairs": 2300,
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"name": "Example Inc.",
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"num_employees": 2300,
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"is_large": False
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},
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{
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"num_chairs": 3,
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"name": "Foobar Ltd.",
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"num_employees": 3,
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"is_large": False
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},
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{
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"num_chairs": 32,
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"name": "Test GmbH",
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"num_employees": 32,
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"is_large": False
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}
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],
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lambda o: o
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)
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# We can perform arithmetic operations in expressions
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# Make sure we have 2 spare chairs
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company_query.update(num_chairs=F("num_employees")+2)
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self.assertQuerysetEqual(
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company_query, [
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{
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'num_chairs': 2302,
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'name': 'Example Inc.',
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'num_employees': 2300,
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'is_large': False
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},
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{
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'num_chairs': 5,
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'name': 'Foobar Ltd.',
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'num_employees': 3,
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'is_large': False
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},
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{
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'num_chairs': 34,
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'name': 'Test GmbH',
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'num_employees': 32,
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'is_large': False
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}
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],
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lambda o: o,
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)
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# Law of order of operations is followed
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company_query.update(
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num_chairs=F('num_employees') + 2 * F('num_employees')
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)
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self.assertQuerysetEqual(
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company_query, [
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{
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'num_chairs': 6900,
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'name': 'Example Inc.',
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'num_employees': 2300,
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'is_large': False
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},
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{
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'num_chairs': 9,
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'name': 'Foobar Ltd.',
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'num_employees': 3,
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'is_large': False
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},
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{
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'num_chairs': 96,
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'name': 'Test GmbH',
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'num_employees': 32,
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'is_large': False
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}
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],
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lambda o: o,
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)
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# Law of order of operations can be overridden by parentheses
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company_query.update(
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num_chairs=((F('num_employees') + 2) * F('num_employees'))
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)
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self.assertQuerysetEqual(
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company_query, [
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{
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'num_chairs': 5294600,
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'name': 'Example Inc.',
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'num_employees': 2300,
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'is_large': False
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},
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{
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'num_chairs': 15,
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'name': 'Foobar Ltd.',
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'num_employees': 3,
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'is_large': False
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},
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{
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'num_chairs': 1088,
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'name': 'Test GmbH',
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'num_employees': 32,
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'is_large': False
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}
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],
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lambda o: o,
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)
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# The comparison operators and the bitwise unary not can be used
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# to assign to boolean fields
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for expression in (
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# Check boundaries
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~(F('num_employees') < 33),
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~(F('num_employees') <= 32),
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(F('num_employees') > 2299),
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(F('num_employees') >= 2300),
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(F('num_employees') == 2300),
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((F('num_employees') + 1 != 4) & (32 != F('num_employees'))),
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# Inverted argument order works too
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(2299 < F('num_employees')),
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(2300 <= F('num_employees'))
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):
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# Test update by F-expression
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company_query.update(
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is_large=expression
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)
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# Compare results
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self.assertQuerysetEqual(
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company_query, [
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{
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'num_chairs': 5294600,
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'name': 'Example Inc.',
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'num_employees': 2300,
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'is_large': True
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},
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{
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'num_chairs': 15,
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'name': 'Foobar Ltd.',
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'num_employees': 3,
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'is_large': False
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},
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{
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'num_chairs': 1088,
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'name': 'Test GmbH',
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'num_employees': 32,
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'is_large': False
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}
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],
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lambda o: o,
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)
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# Reset values
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company_query.update(
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is_large=False
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)
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# The python boolean operators should be avoided as they yield
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# unexpected results
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test_gmbh = Company.objects.get(name="Test GmbH")
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with self.assertRaises(TypeError):
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test_gmbh.is_large = not F('is_large')
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with self.assertRaises(TypeError):
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test_gmbh.is_large = F('is_large') and F('is_large')
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with self.assertRaises(TypeError):
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test_gmbh.is_large = F('is_large') or F('is_large')
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# The relation of a foreign key can become copied over to an other
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# foreign key.
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self.assertEqual(
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Company.objects.update(point_of_contact=F('ceo')),
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3
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)
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self.assertQuerysetEqual(
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Company.objects.all(), [
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"Joe Smith",
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"Frank Meyer",
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"Max Mustermann",
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],
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lambda c: six.text_type(c.point_of_contact),
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)
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c = Company.objects.all()[0]
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c.point_of_contact = Employee.objects.create(firstname="Guido", lastname="van Rossum")
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c.save()
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# F Expressions can also span joins
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self.assertQuerysetEqual(
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Company.objects.filter(ceo__firstname=F("point_of_contact__firstname")), [
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"Foobar Ltd.",
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"Test GmbH",
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],
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lambda c: c.name
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)
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Company.objects.exclude(
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ceo__firstname=F("point_of_contact__firstname")
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).update(name="foo")
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self.assertEqual(
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Company.objects.exclude(
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ceo__firstname=F('point_of_contact__firstname')
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).get().name,
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"foo",
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)
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self.assertRaises(FieldError,
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lambda: Company.objects.exclude(
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ceo__firstname=F('point_of_contact__firstname')
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).update(name=F('point_of_contact__lastname'))
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)
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# F expressions can be used to update attributes on single objects
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test_gmbh = Company.objects.get(name="Test GmbH")
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self.assertEqual(test_gmbh.num_employees, 32)
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test_gmbh.num_employees = F("num_employees") + 4
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test_gmbh.save()
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test_gmbh = Company.objects.get(pk=test_gmbh.pk)
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self.assertEqual(test_gmbh.num_employees, 36)
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# F expressions cannot be used to update attributes which are foreign
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# keys, or attributes which involve joins.
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test_gmbh.point_of_contact = None
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test_gmbh.save()
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self.assertTrue(test_gmbh.point_of_contact is None)
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with self.assertRaises(ValueError):
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test_gmbh.point_of_contact = F("ceo")
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test_gmbh.point_of_contact = test_gmbh.ceo
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test_gmbh.save()
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test_gmbh.name = F("ceo__last_name")
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self.assertRaises(FieldError, test_gmbh.save)
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# F expressions cannot be used to update attributes on objects which do
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# not yet exist in the database
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acme = Company(
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name="The Acme Widget Co.", num_employees=12, num_chairs=5,
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ceo=test_gmbh.ceo
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)
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acme.num_employees = F("num_employees") + 16
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self.assertRaises(TypeError, acme.save)
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