Fixes #2737 -- Added code to allow None as a query value for __exact queries, raising an error otherwise. __exact=None is interpreted as the SQL 'value = NULL'. This fixes some minor problems with queries on unsaved objects with related object sets, and stops queries with a value of None being outright ignored (even if they reference an unknown attribute).

git-svn-id: http://code.djangoproject.com/svn/django/trunk@3902 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Russell Keith-Magee 2006-10-14 02:48:05 +00:00
parent 73a6eb8ed0
commit fbbbf8b9a1
4 changed files with 97 additions and 27 deletions

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@ -707,30 +707,35 @@ def parse_lookup(kwarg_items, opts):
joins, where, params = SortedDict(), [], [] joins, where, params = SortedDict(), [], []
for kwarg, value in kwarg_items: for kwarg, value in kwarg_items:
if value is not None: path = kwarg.split(LOOKUP_SEPARATOR)
path = kwarg.split(LOOKUP_SEPARATOR) # Extract the last elements of the kwarg.
# Extract the last elements of the kwarg. # The very-last is the lookup_type (equals, like, etc).
# The very-last is the lookup_type (equals, like, etc). # The second-last is the table column on which the lookup_type is
# The second-last is the table column on which the lookup_type is # to be performed. If this name is 'pk', it will be substituted with
# to be performed. If this name is 'pk', it will be substituted with # the name of the primary key.
# the name of the primary key. # If there is only one part, or the last part is not a query
# If there is only one part, or the last part is not a query # term, assume that the query is an __exact
# term, assume that the query is an __exact lookup_type = path.pop()
lookup_type = path.pop() if lookup_type == 'pk':
if lookup_type == 'pk': lookup_type = 'exact'
lookup_type = 'exact' path.append(None)
path.append(None) elif len(path) == 0 or lookup_type not in QUERY_TERMS:
elif len(path) == 0 or lookup_type not in QUERY_TERMS: path.append(lookup_type)
path.append(lookup_type) lookup_type = 'exact'
lookup_type = 'exact'
if len(path) < 1: if len(path) < 1:
raise TypeError, "Cannot parse keyword query %r" % kwarg raise TypeError, "Cannot parse keyword query %r" % kwarg
if value is None:
# Interpret '__exact=None' as the sql '= NULL'; otherwise, reject
# all uses of None as a query value.
if lookup_type != 'exact':
raise ValueError, "Cannot use None as a query value"
joins2, where2, params2 = lookup_inner(path, lookup_type, value, opts, opts.db_table, None) joins2, where2, params2 = lookup_inner(path, lookup_type, value, opts, opts.db_table, None)
joins.update(joins2) joins.update(joins2)
where.extend(where2) where.extend(where2)
params.extend(params2) params.extend(params2)
return joins, where, params return joins, where, params
class FieldFound(Exception): class FieldFound(Exception):

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@ -876,15 +876,18 @@ The database API supports the following lookup types:
exact exact
~~~~~ ~~~~~
Exact match. Exact match. If the value provided for comparison is ``None``, it will
be interpreted as an SQL ``NULL`` (See isnull_ for more details).
Example:: Examples::
Entry.objects.get(id__exact=14) Entry.objects.get(id__exact=14)
Entry.objects.get(id__exact=None)
SQL equivalent:: SQL equivalents::
SELECT ... WHERE id = 14; SELECT ... WHERE id = 14;
SELECT ... WHERE id = NULL;
iexact iexact
~~~~~~ ~~~~~~
@ -1103,8 +1106,8 @@ such as January 3, July 3, etc.
isnull isnull
~~~~~~ ~~~~~~
``NULL`` or ``IS NOT NULL`` match. Takes either ``True`` or ``False``, which Takes either ``True`` or ``False``, which correspond to SQL queries of
correspond to ``IS NULL`` and ``IS NOT NULL``, respectively. ``IS NULL`` and ``IS NOT NULL``, respectively.
Example:: Example::
@ -1114,6 +1117,14 @@ SQL equivalent::
SELECT ... WHERE pub_date IS NULL; SELECT ... WHERE pub_date IS NULL;
.. admonition:: ``__isnull=True`` vs ``__exact=None``
There is an important difference between ``__isnull=True`` and
``__exact=None``. ``__exact=None`` will *always* return an empty result
set, because SQL requires that no value is equal to ``NULL``.
``__isnull`` determines if the field is currently holding the value
of ``NULL`` without performing a comparison.
search search
~~~~~~ ~~~~~~

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@ -0,0 +1,54 @@
from django.db import models
class Poll(models.Model):
question = models.CharField(maxlength=200)
def __str__(self):
return "Q: %s " % self.question
class Choice(models.Model):
poll = models.ForeignKey(Poll)
choice = models.CharField(maxlength=200)
def __str__(self):
return "Choice: %s in poll %s" % (self.choice, self.poll)
__test__ = {'API_TESTS':"""
# Regression test for the use of None as a query value. None is interpreted as
# an SQL NULL, but only in __exact queries.
# Set up some initial polls and choices
>>> p1 = Poll(question='Why?')
>>> p1.save()
>>> c1 = Choice(poll=p1, choice='Because.')
>>> c1.save()
>>> c2 = Choice(poll=p1, choice='Why Not?')
>>> c2.save()
# Exact query with value None returns nothing (=NULL in sql)
>>> Choice.objects.filter(id__exact=None)
[]
# Valid query, but fails because foo isn't a keyword
>>> Choice.objects.filter(foo__exact=None)
Traceback (most recent call last):
...
TypeError: Cannot resolve keyword 'foo' into field
# Can't use None on anything other than __exact
>>> Choice.objects.filter(id__gt=None)
Traceback (most recent call last):
...
ValueError: Cannot use None as a query value
# Can't use None on anything other than __exact
>>> Choice.objects.filter(foo__gt=None)
Traceback (most recent call last):
...
ValueError: Cannot use None as a query value
# Related managers use __exact=None implicitly if the object hasn't been saved.
>>> p2 = Poll(question="How?")
>>> p2.choice_set.all()
[]
"""}