Fixed #19195 -- Allow explicit ordering by a relation `_id` field. (24ec9538) · Commits · Dom Sekotill / django

django/db/models/sql/compiler.py

+3 −2

Original line number	Diff line number	Diff line
		@@ -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()

docs/ref/models/querysets.txt

+27 −0

Original line number	Diff line number	Diff line
		@@ -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
		~~~~~~

docs/releases/1.7.txt

+3 −0

Original line number	Diff line number	Diff line
		@@ -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
		^^^^^^^

tests/ordering/models.py

+5 −11

Original line number	Diff line number	Diff line
		@@ -17,25 +17,19 @@ from django.db import models
		from django.utils.encoding import python_2_unicode_compatible


		@python_2_unicode_compatible
		class Article(models.Model):
		headline = models.CharField(max_length=100)
		pub_date = models.DateTimeField()

		class Author(models.Model):
		class Meta:
		ordering = ('-pub_date', 'headline')

		def __str__(self):
		return self.headline
		ordering = ('-pk',)


		@python_2_unicode_compatible
		class ArticlePKOrdering(models.Model):
		class Article(models.Model):
		author = models.ForeignKey(Author, null=True)
		headline = models.CharField(max_length=100)
		pub_date = models.DateTimeField()

		class Meta:
		ordering = ('-pk',)
		ordering = ('-pub_date', 'headline')

		def __str__(self):
		return self.headline

tests/ordering/tests.py

+75 −37

Original line number	Diff line number	Diff line
		@@ -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(
		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(
		ArticlePKOrdering.objects.all(), [
		Article.objects.order_by('author_id'), [
		"Article 4",
		"Article 3",
		"Article 2",