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Code Issues 25 Releases Wiki Activity

Fixed #19195 -- Allow explicit ordering by a relation _id field.

Browse Source 
Thanks to chrisedgemon for the report and shaib, akaariai and
timgraham for the review.
This commit is contained in:
Simon Charette 2014-04-26 03:34:20 -04:00
parent a5f6cbce07
commit 24ec9538b7
5 changed files with 115 additions and 52 deletions
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5
django/db/models/sql/compiler.py
View File

@ -464,8 +464,9 @@ class SQLCompiler(object):
field, targets, alias, joins, path, opts = self._setup_joins(pieces, opts, alias)
# If we get to this point and the field is a relation to another model,
# append the default ordering for that model.
if field.rel and path and opts.ordering:
# append the default ordering for that model unless the attribute name
# of the field is specified.
if field.rel and path and opts.ordering and name != field.attname:
# Firstly, avoid infinite loops.
if not already_seen:
already_seen = set()

27
docs/ref/models/querysets.txt
View File

@ -294,6 +294,18 @@ primary key if there is no :attr:`Meta.ordering
...since the ``Blog`` model has no default ordering specified.
.. versionadded:: 1.7
Note that it is also possible to order a queryset by a related field,
without incurring the cost of a JOIN, by referring to the ``_id`` of the
related field::
# No Join
Entry.objects.order_by('blog_id')
# Join
Entry.objects.order_by('blog__id')
Be cautious when ordering by fields in related models if you are also using
:meth:`distinct()`. See the note in :meth:`distinct` for an explanation of how
related model ordering can change the expected results.
@ -435,6 +447,21 @@ Examples (those after the first will only work on PostgreSQL)::
>>> Entry.objects.order_by('author', 'pub_date').distinct('author')
[...]
.. note::
Keep in mind that :meth:`order_by` uses any default related model ordering
that has been defined. You might have to explicitly order by the relation
``_id`` or referenced field to make sure the ``DISTINCT ON`` expressions
match those at the beginning of the ``ORDER BY`` clause. For example, if
the ``Blog`` model defined an :attr:`~django.db.models.Options.ordering` by
``name``::
Entry.objects.order_by('blog').distinct('blog')
...wouldn't work because the query would be ordered by ``blog__name`` thus
mismatching the ``DISTINCT ON`` expression. You'd have to explicitly order
by the relation `_id` field (``blog_id`` in this case) or the referenced
one (``blog__pk``) to make sure both expressions match.
values
~~~~~~

3
docs/releases/1.7.txt
View File

@ -702,6 +702,9 @@ Models
Previously model field validation didn't prevent values out of their associated
column data type range from being saved resulting in an integrity error.
* It is now possible to explicitly :meth:`~django.db.models.query.QuerySet.order_by`
a relation ``_id`` field by using its attribute name.
Signals
^^^^^^^

18
tests/ordering/models.py
View File

@ -17,8 +17,14 @@ from django.db import models
from django.utils.encoding import python_2_unicode_compatible
class Author(models.Model):
class Meta:
ordering = ('-pk',)
@python_2_unicode_compatible
class Article(models.Model):
author = models.ForeignKey(Author, null=True)
headline = models.CharField(max_length=100)
pub_date = models.DateTimeField()
@ -27,15 +33,3 @@ class Article(models.Model):
def __str__(self):
return self.headline
@python_2_unicode_compatible
class ArticlePKOrdering(models.Model):
headline = models.CharField(max_length=100)
pub_date = models.DateTimeField()
class Meta:
ordering = ('-pk',)
def __str__(self):
return self.headline

114
tests/ordering/tests.py
View File

@ -5,26 +5,29 @@ from operator import attrgetter
from django.test import TestCase
from .models import Article, ArticlePKOrdering
from .models import Article, Author
class OrderingTests(TestCase):
def test_basic(self):
Article.objects.create(
def setUp(self):
self.a1 = Article.objects.create(
headline="Article 1", pub_date=datetime(2005, 7, 26)
)
Article.objects.create(
self.a2 = Article.objects.create(
headline="Article 2", pub_date=datetime(2005, 7, 27)
)
Article.objects.create(
self.a3 = Article.objects.create(
headline="Article 3", pub_date=datetime(2005, 7, 27)
)
a4 = Article.objects.create(
self.a4 = Article.objects.create(
headline="Article 4", pub_date=datetime(2005, 7, 28)
)
# By default, Article.objects.all() orders by pub_date descending, then
# headline ascending.
def test_default_ordering(self):
"""
By default, Article.objects.all() orders by pub_date descending, then
headline ascending.
"""
self.assertQuerysetEqual(
Article.objects.all(), [
"Article 4",
@ -35,8 +38,14 @@ class OrderingTests(TestCase):
attrgetter("headline")
)
# Override ordering with order_by, which is in the same format as the
# ordering attribute in models.
# Getting a single item should work too:
self.assertEqual(Article.objects.all()[0], self.a4)
def test_default_ordering_override(self):
"""
Override ordering with order_by, which is in the same format as the
ordering attribute in models.
"""
self.assertQuerysetEqual(
Article.objects.order_by("headline"), [
"Article 1",
@ -56,8 +65,11 @@ class OrderingTests(TestCase):
attrgetter("headline")
)
# Only the last order_by has any effect (since they each override any
# previous ordering).
def test_order_by_override(self):
"""
Only the last order_by has any effect (since they each override any
previous ordering).
"""
self.assertQuerysetEqual(
Article.objects.order_by("id"), [
"Article 1",
@ -77,7 +89,10 @@ class OrderingTests(TestCase):
attrgetter("headline")
)
# Use the 'stop' part of slicing notation to limit the results.
def test_stop_slicing(self):
"""
Use the 'stop' part of slicing notation to limit the results.
"""
self.assertQuerysetEqual(
Article.objects.order_by("headline")[:2], [
"Article 1",
@ -86,8 +101,11 @@ class OrderingTests(TestCase):
attrgetter("headline")
)
# Use the 'stop' and 'start' parts of slicing notation to offset the
# result list.
def test_stop_start_slicing(self):
"""
Use the 'stop' and 'start' parts of slicing notation to offset the
result list.
"""
self.assertQuerysetEqual(
Article.objects.order_by("headline")[1:3], [
"Article 2",
@ -96,17 +114,20 @@ class OrderingTests(TestCase):
attrgetter("headline")
)
# Getting a single item should work too:
self.assertEqual(Article.objects.all()[0], a4)
# Use '?' to order randomly.
def test_random_ordering(self):
"""
Use '?' to order randomly.
"""
self.assertEqual(
len(list(Article.objects.order_by("?"))), 4
)
# Ordering can be reversed using the reverse() method on a queryset.
# This allows you to extract things like "the last two items" (reverse
# and then take the first two).
def test_reversed_ordering(self):
"""
Ordering can be reversed using the reverse() method on a queryset.
This allows you to extract things like "the last two items" (reverse
and then take the first two).
"""
self.assertQuerysetEqual(
Article.objects.all().reverse()[:2], [
"Article 1",
@ -115,7 +136,10 @@ class OrderingTests(TestCase):
attrgetter("headline")
)
# Ordering can be based on fields included from an 'extra' clause
def test_extra_ordering(self):
"""
Ordering can be based on fields included from an 'extra' clause
"""
self.assertQuerysetEqual(
Article.objects.extra(select={"foo": "pub_date"}, order_by=["foo", "headline"]), [
"Article 1",
@ -126,8 +150,11 @@ class OrderingTests(TestCase):
attrgetter("headline")
)
# If the extra clause uses an SQL keyword for a name, it will be
# protected by quoting.
def test_extra_ordering_quoting(self):
"""
If the extra clause uses an SQL keyword for a name, it will be
protected by quoting.
"""
self.assertQuerysetEqual(
Article.objects.extra(select={"order": "pub_date"}, order_by=["order", "headline"]), [
"Article 1",
@ -143,21 +170,32 @@ class OrderingTests(TestCase):
Ensure that 'pk' works as an ordering option in Meta.
Refs #8291.
"""
ArticlePKOrdering.objects.create(
pk=1, headline="Article 1", pub_date=datetime(2005, 7, 26)
)
ArticlePKOrdering.objects.create(
pk=2, headline="Article 2", pub_date=datetime(2005, 7, 27)
)
ArticlePKOrdering.objects.create(
pk=3, headline="Article 3", pub_date=datetime(2005, 7, 27)
)
ArticlePKOrdering.objects.create(
pk=4, headline="Article 4", pub_date=datetime(2005, 7, 28)
)
Author.objects.create(pk=1)
Author.objects.create(pk=2)
Author.objects.create(pk=3)
Author.objects.create(pk=4)
self.assertQuerysetEqual(
ArticlePKOrdering.objects.all(), [
Author.objects.all(), [
4, 3, 2, 1
],
attrgetter("pk")
)
def test_order_by_fk_attname(self):
"""
Ensure that ordering by a foreign key by its attribute name prevents
the query from inheriting it's related model ordering option.
Refs #19195.
"""
for i in range(1, 5):
author = Author.objects.create(pk=i)
article = getattr(self, "a%d" % (5 - i))
article.author = author
article.save(update_fields={'author'})
self.assertQuerysetEqual(
Article.objects.order_by('author_id'), [
"Article 4",
"Article 3",
"Article 2",