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django/tests/modeltests/expressions/tests.py
Anssi Kääriäinen 90b86291d0 Fixed #18375 -- Removed dict-ordering dependency for F-expressions
F() expressions reuse joins like any lookup in a .filter() call -
reuse multijoins generated in the same .filter() call else generate
new joins. Also, lookups can now reuse joins generated by F().

This change is backwards incompatible, but it is required to prevent
dict randomization from generating different queries depending on
.filter() kwarg ordering. The new way is also more consistent in how
joins are reused.
2012-11-23 19:53:04 +02:00

261 lines
9.0 KiB
Python

from __future__ import absolute_import, unicode_literals
from django.core.exceptions import FieldError
from django.db.models import F
from django.test import TestCase
from django.utils import six
from .models import Company, Employee
class ExpressionsTests(TestCase):
def test_filter(self):
Company.objects.create(
name="Example Inc.", num_employees=2300, num_chairs=5,
ceo=Employee.objects.create(firstname="Joe", lastname="Smith")
)
Company.objects.create(
name="Foobar Ltd.", num_employees=3, num_chairs=4,
ceo=Employee.objects.create(firstname="Frank", lastname="Meyer")
)
Company.objects.create(
name="Test GmbH", num_employees=32, num_chairs=1,
ceo=Employee.objects.create(firstname="Max", lastname="Mustermann")
)
company_query = Company.objects.values(
"name", "num_employees", "num_chairs"
).order_by(
"name", "num_employees", "num_chairs"
)
# We can filter for companies where the number of employees is greater
# than the number of chairs.
self.assertQuerysetEqual(
company_query.filter(num_employees__gt=F("num_chairs")), [
{
"num_chairs": 5,
"name": "Example Inc.",
"num_employees": 2300,
},
{
"num_chairs": 1,
"name": "Test GmbH",
"num_employees": 32
},
],
lambda o: o
)
# We can set one field to have the value of another field
# Make sure we have enough chairs
company_query.update(num_chairs=F("num_employees"))
self.assertQuerysetEqual(
company_query, [
{
"num_chairs": 2300,
"name": "Example Inc.",
"num_employees": 2300
},
{
"num_chairs": 3,
"name": "Foobar Ltd.",
"num_employees": 3
},
{
"num_chairs": 32,
"name": "Test GmbH",
"num_employees": 32
}
],
lambda o: o
)
# We can perform arithmetic operations in expressions
# Make sure we have 2 spare chairs
company_query.update(num_chairs=F("num_employees")+2)
self.assertQuerysetEqual(
company_query, [
{
'num_chairs': 2302,
'name': 'Example Inc.',
'num_employees': 2300
},
{
'num_chairs': 5,
'name': 'Foobar Ltd.',
'num_employees': 3
},
{
'num_chairs': 34,
'name': 'Test GmbH',
'num_employees': 32
}
],
lambda o: o,
)
# Law of order of operations is followed
company_query.update(
num_chairs=F('num_employees') + 2 * F('num_employees')
)
self.assertQuerysetEqual(
company_query, [
{
'num_chairs': 6900,
'name': 'Example Inc.',
'num_employees': 2300
},
{
'num_chairs': 9,
'name': 'Foobar Ltd.',
'num_employees': 3
},
{
'num_chairs': 96,
'name': 'Test GmbH',
'num_employees': 32
}
],
lambda o: o,
)
# Law of order of operations can be overridden by parentheses
company_query.update(
num_chairs=((F('num_employees') + 2) * F('num_employees'))
)
self.assertQuerysetEqual(
company_query, [
{
'num_chairs': 5294600,
'name': 'Example Inc.',
'num_employees': 2300
},
{
'num_chairs': 15,
'name': 'Foobar Ltd.',
'num_employees': 3
},
{
'num_chairs': 1088,
'name': 'Test GmbH',
'num_employees': 32
}
],
lambda o: o,
)
# The relation of a foreign key can become copied over to an other
# foreign key.
self.assertEqual(
Company.objects.update(point_of_contact=F('ceo')),
3
)
self.assertQuerysetEqual(
Company.objects.all(), [
"Joe Smith",
"Frank Meyer",
"Max Mustermann",
],
lambda c: six.text_type(c.point_of_contact),
)
c = Company.objects.all()[0]
c.point_of_contact = Employee.objects.create(firstname="Guido", lastname="van Rossum")
c.save()
# F Expressions can also span joins
self.assertQuerysetEqual(
Company.objects.filter(ceo__firstname=F("point_of_contact__firstname")), [
"Foobar Ltd.",
"Test GmbH",
],
lambda c: c.name
)
Company.objects.exclude(
ceo__firstname=F("point_of_contact__firstname")
).update(name="foo")
self.assertEqual(
Company.objects.exclude(
ceo__firstname=F('point_of_contact__firstname')
).get().name,
"foo",
)
self.assertRaises(FieldError,
lambda: Company.objects.exclude(
ceo__firstname=F('point_of_contact__firstname')
).update(name=F('point_of_contact__lastname'))
)
# F expressions can be used to update attributes on single objects
test_gmbh = Company.objects.get(name="Test GmbH")
self.assertEqual(test_gmbh.num_employees, 32)
test_gmbh.num_employees = F("num_employees") + 4
test_gmbh.save()
test_gmbh = Company.objects.get(pk=test_gmbh.pk)
self.assertEqual(test_gmbh.num_employees, 36)
# F expressions cannot be used to update attributes which are foreign
# keys, or attributes which involve joins.
test_gmbh.point_of_contact = None
test_gmbh.save()
self.assertTrue(test_gmbh.point_of_contact is None)
def test():
test_gmbh.point_of_contact = F("ceo")
self.assertRaises(ValueError, test)
test_gmbh.point_of_contact = test_gmbh.ceo
test_gmbh.save()
test_gmbh.name = F("ceo__last_name")
self.assertRaises(FieldError, test_gmbh.save)
# F expressions cannot be used to update attributes on objects which do
# not yet exist in the database
acme = Company(
name="The Acme Widget Co.", num_employees=12, num_chairs=5,
ceo=test_gmbh.ceo
)
acme.num_employees = F("num_employees") + 16
self.assertRaises(TypeError, acme.save)
def test_ticket_18375_join_reuse(self):
# Test that reverse multijoin F() references and the lookup target
# the same join. Pre #18375 the F() join was generated first, and the
# lookup couldn't reuse that join.
qs = Employee.objects.filter(
company_ceo_set__num_chairs=F('company_ceo_set__num_employees'))
self.assertEqual(str(qs.query).count('JOIN'), 1)
def test_ticket_18375_kwarg_ordering(self):
# The next query was dict-randomization dependent - if the "gte=1"
# was seen first, then the F() will reuse the join generated by the
# gte lookup, if F() was seen first, then it generated a join the
# other lookups could not reuse.
qs = Employee.objects.filter(
company_ceo_set__num_chairs=F('company_ceo_set__num_employees'),
company_ceo_set__num_chairs__gte=1)
self.assertEqual(str(qs.query).count('JOIN'), 1)
def test_ticket_18375_kwarg_ordering_2(self):
# Another similar case for F() than above. Now we have the same join
# in two filter kwargs, one in the lhs lookup, one in F. Here pre
# #18375 the amount of joins generated was random if dict
# randomization was enabled, that is the generated query dependend
# on which clause was seen first.
qs = Employee.objects.filter(
company_ceo_set__num_employees=F('pk'),
pk=F('company_ceo_set__num_employees')
)
self.assertEqual(str(qs.query).count('JOIN'), 1)
def test_ticket_18375_chained_filters(self):
# Test that F() expressions do not reuse joins from previous filter.
qs = Employee.objects.filter(
company_ceo_set__num_employees=F('pk')
).filter(
company_ceo_set__num_employees=F('company_ceo_set__num_employees')
)
self.assertEqual(str(qs.query).count('JOIN'), 2)