From fbbbf8b9a14ebd5752529009523729e7d87989e8 Mon Sep 17 00:00:00 2001
From: Russell Keith-Magee <russell@keith-magee.com>
Date: Sat, 14 Oct 2006 02:48:05 +0000
Subject: [PATCH] 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
---
django/db/models/query.py | 49 +++++++++--------
docs/db-api.txt | 21 ++++++--
.../regressiontests/null_queries/__init__.py | 0
tests/regressiontests/null_queries/models.py | 54 +++++++++++++++++++
4 files changed, 97 insertions(+), 27 deletions(-)
create mode 100644 tests/regressiontests/null_queries/__init__.py
create mode 100644 tests/regressiontests/null_queries/models.py
diff --git a/django/db/models/query.py b/django/db/models/query.py
index eb4b3b63ae..53ed63ae5b 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -707,30 +707,35 @@ def parse_lookup(kwarg_items, opts):
joins, where, params = SortedDict(), [], []
for kwarg, value in kwarg_items:
- if value is not None:
- path = kwarg.split(LOOKUP_SEPARATOR)
- # Extract the last elements of the kwarg.
- # The very-last is the lookup_type (equals, like, etc).
- # 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
- # the name of the primary key.
- # If there is only one part, or the last part is not a query
- # term, assume that the query is an __exact
- lookup_type = path.pop()
- if lookup_type == 'pk':
- lookup_type = 'exact'
- path.append(None)
- elif len(path) == 0 or lookup_type not in QUERY_TERMS:
- path.append(lookup_type)
- lookup_type = 'exact'
+ path = kwarg.split(LOOKUP_SEPARATOR)
+ # Extract the last elements of the kwarg.
+ # The very-last is the lookup_type (equals, like, etc).
+ # 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
+ # the name of the primary key.
+ # If there is only one part, or the last part is not a query
+ # term, assume that the query is an __exact
+ lookup_type = path.pop()
+ if lookup_type == 'pk':
+ lookup_type = 'exact'
+ path.append(None)
+ elif len(path) == 0 or lookup_type not in QUERY_TERMS:
+ path.append(lookup_type)
+ lookup_type = 'exact'
- if len(path) < 1:
- raise TypeError, "Cannot parse keyword query %r" % kwarg
+ if len(path) < 1:
+ 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)
- joins.update(joins2)
- where.extend(where2)
- params.extend(params2)
+ joins2, where2, params2 = lookup_inner(path, lookup_type, value, opts, opts.db_table, None)
+ joins.update(joins2)
+ where.extend(where2)
+ params.extend(params2)
return joins, where, params
class FieldFound(Exception):
diff --git a/docs/db-api.txt b/docs/db-api.txt
index 0d1f049601..2f0c8b0589 100644
--- a/docs/db-api.txt
+++ b/docs/db-api.txt
@@ -876,15 +876,18 @@ The database API supports the following lookup types:
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=None)
-SQL equivalent::
+SQL equivalents::
SELECT ... WHERE id = 14;
+ SELECT ... WHERE id = NULL;
iexact
~~~~~~
@@ -1103,8 +1106,8 @@ such as January 3, July 3, etc.
isnull
~~~~~~
-``NULL`` or ``IS NOT NULL`` match. Takes either ``True`` or ``False``, which
-correspond to ``IS NULL`` and ``IS NOT NULL``, respectively.
+Takes either ``True`` or ``False``, which correspond to SQL queries of
+``IS NULL`` and ``IS NOT NULL``, respectively.
Example::
@@ -1114,6 +1117,14 @@ SQL equivalent::
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
~~~~~~
diff --git a/tests/regressiontests/null_queries/__init__.py b/tests/regressiontests/null_queries/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/regressiontests/null_queries/models.py b/tests/regressiontests/null_queries/models.py
new file mode 100644
index 0000000000..09024f18c2
--- /dev/null
+++ b/tests/regressiontests/null_queries/models.py
@@ -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()
+[]
+
+"""}