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Fixed #16211 -- Added comparison and negation ops to F() expressions 

Work done by Walter Doekes and Trac alias knoeb. Reviewed by Simon
Charette.
This commit is contained in:
Anssi Kääriäinen 2012-09-30 17:51:06 +03:00
parent ddd7d1af20
commit 28abf5f0eb
7 changed files with 150 additions and 22 deletions
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3
django/db/backends/__init__.py
View File

@ -913,6 +913,9 @@ class BaseDatabaseOperations(object):
can vary between backends (e.g., Oracle with %% and &) and between
subexpression types (e.g., date expressions)
"""
if connector == 'NOT':
assert len(sub_expressions) == 1
return 'NOT (%s)' % sub_expressions[0]
conn = ' %s ' % connector
return conn.join(sub_expressions)

37
django/db/models/expressions.py
View File

@ -18,6 +18,17 @@ class ExpressionNode(tree.Node):
AND = '&'
OR = '|'
# Unary operator (needs special attention in combine_expression)
NOT = 'NOT'
# Comparison operators
EQ = '='
GE = '>='
GT = '>'
LE = '<='
LT = '<'
NE = '<>'
def __init__(self, children=None, connector=None, negated=False):
if children is not None and len(children) > 1 and connector is None:
raise TypeError('You have to specify a connector.')
@ -93,6 +104,32 @@ class ExpressionNode(tree.Node):
def __ror__(self, other):
return self._combine(other, self.OR, True)
def __invert__(self):
obj = ExpressionNode([self], connector=self.NOT, negated=True)
return obj
def __eq__(self, other):
return self._combine(other, self.EQ, False)
def __ge__(self, other):
return self._combine(other, self.GE, False)
def __gt__(self, other):
return self._combine(other, self.GT, False)
def __le__(self, other):
return self._combine(other, self.LE, False)
def __lt__(self, other):
return self._combine(other, self.LT, False)
def __ne__(self, other):
return self._combine(other, self.NE, False)
def __bool__(self):
raise TypeError('Boolean operators should be avoided. Use bitwise operators.')
__nonzero__ = __bool__
def prepare_database_save(self, unused):
return self

8
django/utils/tree.py
View File

@ -88,8 +88,12 @@ class Node(object):
Otherwise, the whole tree is pushed down one level and a new root
connector is created, connecting the existing tree and the new node.
"""
if node in self.children and conn_type == self.connector:
return
# Using for loop with 'is' instead of 'if node in children' so node
# __eq__ method doesn't get called. The __eq__ method can be overriden
# by subtypes, for example the F-expression.
for child in self.children:
if node is child and conn_type == self.connector:
return
if len(self.children) < 2:
self.connector = conn_type
if self.connector == conn_type:

4
docs/releases/1.5.txt
View File

@ -176,6 +176,10 @@ Django 1.5 also includes several smaller improvements worth noting:
:setting:`DEBUG` is `True` are sent to the console (unless you redefine the
logger in your :setting:`LOGGING` setting).
* :ref:`F() expressions <query-expressions>` now support comparison operations
and inversion, expanding the types of expressions that can be passed to the
database.
Backwards incompatible changes in 1.5
=====================================

9
docs/topics/db/queries.txt
View File

@ -640,6 +640,15 @@ that were modified more than 3 days after they were published::
>>> from datetime import timedelta
>>> Entry.objects.filter(mod_date__gt=F('pub_date') + timedelta(days=3))
.. versionadded:: 1.5
Comparisons and negation operators for ``F()`` expressions
Django also supports the comparison operators ``==``, ``!=``, ``<=``, ``<``,
``>``, ``>=`` and the bitwise negation operator ``~`` (boolean ``not`` operator
will raise ``TypeError``)::
>>> Entry.objects.filter(is_heavily_quoted=~(F('n_pingbacks') < 100))
The pk lookup shortcut
----------------------

2
tests/modeltests/expressions/models.py
View File

@ -27,6 +27,8 @@ class Company(models.Model):
Employee,
related_name='company_point_of_contact_set',
null=True)
is_large = models.BooleanField(
blank=True)
def __str__(self):
return self.name

109
tests/modeltests/expressions/tests.py
View File

@ -11,22 +11,22 @@ from .models import Company, Employee
class ExpressionsTests(TestCase):
def test_filter(self):
Company.objects.create(
name="Example Inc.", num_employees=2300, num_chairs=5,
name="Example Inc.", num_employees=2300, num_chairs=5, is_large=False,
ceo=Employee.objects.create(firstname="Joe", lastname="Smith")
)
Company.objects.create(
name="Foobar Ltd.", num_employees=3, num_chairs=4,
name="Foobar Ltd.", num_employees=3, num_chairs=4, is_large=False,
ceo=Employee.objects.create(firstname="Frank", lastname="Meyer")
)
Company.objects.create(
name="Test GmbH", num_employees=32, num_chairs=1,
name="Test GmbH", num_employees=32, num_chairs=1, is_large=False,
ceo=Employee.objects.create(firstname="Max", lastname="Mustermann")
)
company_query = Company.objects.values(
"name", "num_employees", "num_chairs"
"name", "num_employees", "num_chairs", "is_large"
).order_by(
"name", "num_employees", "num_chairs"
"name", "num_employees", "num_chairs", "is_large"
)
# We can filter for companies where the number of employees is greater
@ -37,11 +37,13 @@ class ExpressionsTests(TestCase):
"num_chairs": 5,
"name": "Example Inc.",
"num_employees": 2300,
"is_large": False
},
{
"num_chairs": 1,
"name": "Test GmbH",
"num_employees": 32
"num_employees": 32,
"is_large": False
},
],
lambda o: o
@ -55,17 +57,20 @@ class ExpressionsTests(TestCase):
{
"num_chairs": 2300,
"name": "Example Inc.",
"num_employees": 2300
"num_employees": 2300,
"is_large": False
},
{
"num_chairs": 3,
"name": "Foobar Ltd.",
"num_employees": 3
"num_employees": 3,
"is_large": False
},
{
"num_chairs": 32,
"name": "Test GmbH",
"num_employees": 32
"num_employees": 32,
"is_large": False
}
],
lambda o: o
@ -79,17 +84,20 @@ class ExpressionsTests(TestCase):
{
'num_chairs': 2302,
'name': 'Example Inc.',
'num_employees': 2300
'num_employees': 2300,
'is_large': False
},
{
'num_chairs': 5,
'name': 'Foobar Ltd.',
'num_employees': 3
'num_employees': 3,
'is_large': False
},
{
'num_chairs': 34,
'name': 'Test GmbH',
'num_employees': 32
'num_employees': 32,
'is_large': False
}
],
lambda o: o,
@ -104,17 +112,20 @@ class ExpressionsTests(TestCase):
{
'num_chairs': 6900,
'name': 'Example Inc.',
'num_employees': 2300
'num_employees': 2300,
'is_large': False
},
{
'num_chairs': 9,
'name': 'Foobar Ltd.',
'num_employees': 3
'num_employees': 3,
'is_large': False
},
{
'num_chairs': 96,
'name': 'Test GmbH',
'num_employees': 32
'num_employees': 32,
'is_large': False
}
],
lambda o: o,
@ -129,21 +140,80 @@ class ExpressionsTests(TestCase):
{
'num_chairs': 5294600,
'name': 'Example Inc.',
'num_employees': 2300
'num_employees': 2300,
'is_large': False
},
{
'num_chairs': 15,
'name': 'Foobar Ltd.',
'num_employees': 3
'num_employees': 3,
'is_large': False
},
{
'num_chairs': 1088,
'name': 'Test GmbH',
'num_employees': 32
'num_employees': 32,
'is_large': False
}
],
lambda o: o,
)
# The comparison operators and the bitwise unary not can be used
# to assign to boolean fields
for expression in (
# Check boundaries
~(F('num_employees') < 33),
~(F('num_employees') <= 32),
(F('num_employees') > 2299),
(F('num_employees') >= 2300),
(F('num_employees') == 2300),
((F('num_employees') + 1 != 4) & (32 != F('num_employees'))),
# Inverted argument order works too
(2299 < F('num_employees')),
(2300 <= F('num_employees'))
):
# Test update by F-expression
company_query.update(
is_large=expression
)
# Compare results
self.assertQuerysetEqual(
company_query, [
{
'num_chairs': 5294600,
'name': 'Example Inc.',
'num_employees': 2300,
'is_large': True
},
{
'num_chairs': 15,
'name': 'Foobar Ltd.',
'num_employees': 3,
'is_large': False
},
{
'num_chairs': 1088,
'name': 'Test GmbH',
'num_employees': 32,
'is_large': False
}
],
lambda o: o,
)
# Reset values
company_query.update(
is_large=False
)
# The python boolean operators should be avoided as they yield
# unexpected results
test_gmbh = Company.objects.get(name="Test GmbH")
with self.assertRaises(TypeError):
test_gmbh.is_large = not F('is_large')
with self.assertRaises(TypeError):
test_gmbh.is_large = F('is_large') and F('is_large')
with self.assertRaises(TypeError):
test_gmbh.is_large = F('is_large') or F('is_large')
# The relation of a foreign key can become copied over to an other
# foreign key.
@ -202,9 +272,8 @@ class ExpressionsTests(TestCase):
test_gmbh.point_of_contact = None
test_gmbh.save()
self.assertTrue(test_gmbh.point_of_contact is None)
def test():
with self.assertRaises(ValueError):
test_gmbh.point_of_contact = F("ceo")
self.assertRaises(ValueError, test)
test_gmbh.point_of_contact = test_gmbh.ceo
test_gmbh.save()