django/tests/aggregation_regress/tests.py

from __future__ import unicode_literals

import datetime
import pickle
from decimal import Decimal
from operator import attrgetter

from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import FieldError
from django.db import connection
from django.db.models import (
    Avg, Count, F, Max, Q, StdDev, Sum, Value, Variance,
)
from django.test import TestCase, skipUnlessAnyDBFeature, skipUnlessDBFeature
from django.test.utils import Approximate
from django.utils import six

from .models import (
    Alfa, Author, Book, Bravo, Charlie, Clues, Entries, HardbackBook, ItemTag,
    Publisher, SelfRefFK, Store, WithManualPK,
)


class AggregationTests(TestCase):

    @classmethod
    def setUpTestData(cls):
        cls.a1 = Author.objects.create(name='Adrian Holovaty', age=34)
        cls.a2 = Author.objects.create(name='Jacob Kaplan-Moss', age=35)
        cls.a3 = Author.objects.create(name='Brad Dayley', age=45)
        cls.a4 = Author.objects.create(name='James Bennett', age=29)
        cls.a5 = Author.objects.create(name='Jeffrey Forcier', age=37)
        cls.a6 = Author.objects.create(name='Paul Bissex', age=29)
        cls.a7 = Author.objects.create(name='Wesley J. Chun', age=25)
        cls.a8 = Author.objects.create(name='Peter Norvig', age=57)
        cls.a9 = Author.objects.create(name='Stuart Russell', age=46)
        cls.a1.friends.add(cls.a2, cls.a4)
        cls.a2.friends.add(cls.a1, cls.a7)
        cls.a4.friends.add(cls.a1)
        cls.a5.friends.add(cls.a6, cls.a7)
        cls.a6.friends.add(cls.a5, cls.a7)
        cls.a7.friends.add(cls.a2, cls.a5, cls.a6)
        cls.a8.friends.add(cls.a9)
        cls.a9.friends.add(cls.a8)

        cls.p1 = Publisher.objects.create(name='Apress', num_awards=3)
        cls.p2 = Publisher.objects.create(name='Sams', num_awards=1)
        cls.p3 = Publisher.objects.create(name='Prentice Hall', num_awards=7)
        cls.p4 = Publisher.objects.create(name='Morgan Kaufmann', num_awards=9)
        cls.p5 = Publisher.objects.create(name="Jonno's House of Books", num_awards=0)

        cls.b1 = Book.objects.create(
            isbn='159059725', name='The Definitive Guide to Django: Web Development Done Right',
            pages=447, rating=4.5, price=Decimal('30.00'), contact=cls.a1, publisher=cls.p1,
            pubdate=datetime.date(2007, 12, 6)
        )
        cls.b2 = Book.objects.create(
            isbn='067232959', name='Sams Teach Yourself Django in 24 Hours',
            pages=528, rating=3.0, price=Decimal('23.09'), contact=cls.a3, publisher=cls.p2,
            pubdate=datetime.date(2008, 3, 3)
        )
        cls.b3 = Book.objects.create(
            isbn='159059996', name='Practical Django Projects',
            pages=300, rating=4.0, price=Decimal('29.69'), contact=cls.a4, publisher=cls.p1,
            pubdate=datetime.date(2008, 6, 23)
        )
        cls.b4 = Book.objects.create(
            isbn='013235613', name='Python Web Development with Django',
            pages=350, rating=4.0, price=Decimal('29.69'), contact=cls.a5, publisher=cls.p3,
            pubdate=datetime.date(2008, 11, 3)
        )
        cls.b5 = HardbackBook.objects.create(
            isbn='013790395', name='Artificial Intelligence: A Modern Approach',
            pages=1132, rating=4.0, price=Decimal('82.80'), contact=cls.a8, publisher=cls.p3,
            pubdate=datetime.date(1995, 1, 15), weight=4.5)
        cls.b6 = HardbackBook.objects.create(
            isbn='155860191', name='Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp',
            pages=946, rating=5.0, price=Decimal('75.00'), contact=cls.a8, publisher=cls.p4,
            pubdate=datetime.date(1991, 10, 15), weight=3.7)
        cls.b1.authors.add(cls.a1, cls.a2)
        cls.b2.authors.add(cls.a3)
        cls.b3.authors.add(cls.a4)
        cls.b4.authors.add(cls.a5, cls.a6, cls.a7)
        cls.b5.authors.add(cls.a8, cls.a9)
        cls.b6.authors.add(cls.a8)

        s1 = Store.objects.create(
            name='Amazon.com',
            original_opening=datetime.datetime(1994, 4, 23, 9, 17, 42),
            friday_night_closing=datetime.time(23, 59, 59)
        )
        s2 = Store.objects.create(
            name='Books.com',
            original_opening=datetime.datetime(2001, 3, 15, 11, 23, 37),
            friday_night_closing=datetime.time(23, 59, 59)
        )
        s3 = Store.objects.create(
            name="Mamma and Pappa's Books",
            original_opening=datetime.datetime(1945, 4, 25, 16, 24, 14),
            friday_night_closing=datetime.time(21, 30)
        )
        s1.books.add(cls.b1, cls.b2, cls.b3, cls.b4, cls.b5, cls.b6)
        s2.books.add(cls.b1, cls.b3, cls.b5, cls.b6)
        s3.books.add(cls.b3, cls.b4, cls.b6)

    def assertObjectAttrs(self, obj, **kwargs):
        for attr, value in six.iteritems(kwargs):
            self.assertEqual(getattr(obj, attr), value)

    def test_aggregates_in_where_clause(self):
        """
        Regression test for #12822: DatabaseError: aggregates not allowed in
        WHERE clause

        The subselect works and returns results equivalent to a
        query with the IDs listed.

        Before the corresponding fix for this bug, this test passed in 1.1 and
        failed in 1.2-beta (trunk).
        """
        qs = Book.objects.values('contact').annotate(Max('id'))
        qs = qs.order_by('contact').values_list('id__max', flat=True)
        # don't do anything with the queryset (qs) before including it as a
        # subquery
        books = Book.objects.order_by('id')
        qs1 = books.filter(id__in=qs)
        qs2 = books.filter(id__in=list(qs))
        self.assertEqual(list(qs1), list(qs2))

    def test_aggregates_in_where_clause_pre_eval(self):
        """
        Regression test for #12822: DatabaseError: aggregates not allowed in
        WHERE clause

        Same as the above test, but evaluates the queryset for the subquery
        before it's used as a subquery.

        Before the corresponding fix for this bug, this test failed in both
        1.1 and 1.2-beta (trunk).
        """
        qs = Book.objects.values('contact').annotate(Max('id'))
        qs = qs.order_by('contact').values_list('id__max', flat=True)
        # force the queryset (qs) for the subquery to be evaluated in its
        # current state
        list(qs)
        books = Book.objects.order_by('id')
        qs1 = books.filter(id__in=qs)
        qs2 = books.filter(id__in=list(qs))
        self.assertEqual(list(qs1), list(qs2))

    @skipUnlessDBFeature('supports_subqueries_in_group_by')
    def test_annotate_with_extra(self):
        """
        Regression test for #11916: Extra params + aggregation creates
        incorrect SQL.
        """
        # Oracle doesn't support subqueries in group by clause
        shortest_book_sql = """
        SELECT name
        FROM aggregation_regress_book b
        WHERE b.publisher_id = aggregation_regress_publisher.id
        ORDER BY b.pages
        LIMIT 1
        """
        # tests that this query does not raise a DatabaseError due to the full
        # subselect being (erroneously) added to the GROUP BY parameters
        qs = Publisher.objects.extra(select={
            'name_of_shortest_book': shortest_book_sql,
        }).annotate(total_books=Count('book'))
        # force execution of the query
        list(qs)

    def test_aggregate(self):
        # Ordering requests are ignored
        self.assertEqual(
            Author.objects.order_by("name").aggregate(Avg("age")),
            {"age__avg": Approximate(37.444, places=1)}
        )

        # Implicit ordering is also ignored
        self.assertEqual(
            Book.objects.aggregate(Sum("pages")),
            {"pages__sum": 3703},
        )

        # Baseline results
        self.assertEqual(
            Book.objects.aggregate(Sum('pages'), Avg('pages')),
            {'pages__sum': 3703, 'pages__avg': Approximate(617.166, places=2)}
        )

        # Empty values query doesn't affect grouping or results
        self.assertEqual(
            Book.objects.values().aggregate(Sum('pages'), Avg('pages')),
            {'pages__sum': 3703, 'pages__avg': Approximate(617.166, places=2)}
        )

        # Aggregate overrides extra selected column
        self.assertEqual(
            Book.objects.extra(select={'price_per_page': 'price / pages'}).aggregate(Sum('pages')),
            {'pages__sum': 3703}
        )

    def test_annotation(self):
        # Annotations get combined with extra select clauses
        obj = Book.objects.annotate(mean_auth_age=Avg("authors__age")).extra(
            select={"manufacture_cost": "price * .5"}).get(pk=self.b2.pk)
        self.assertObjectAttrs(
            obj,
            contact_id=self.a3.id,
            isbn='067232959',
            mean_auth_age=45.0,
            name='Sams Teach Yourself Django in 24 Hours',
            pages=528,
            price=Decimal("23.09"),
            pubdate=datetime.date(2008, 3, 3),
            publisher_id=self.p2.id,
            rating=3.0
        )
        # Different DB backends return different types for the extra select computation
        self.assertIn(obj.manufacture_cost, (11.545, Decimal('11.545')))

        # Order of the annotate/extra in the query doesn't matter
        obj = Book.objects.extra(select={'manufacture_cost': 'price * .5'}).annotate(
            mean_auth_age=Avg('authors__age')).get(pk=self.b2.pk)
        self.assertObjectAttrs(
            obj,
            contact_id=self.a3.id,
            isbn='067232959',
            mean_auth_age=45.0,
            name='Sams Teach Yourself Django in 24 Hours',
            pages=528,
            price=Decimal("23.09"),
            pubdate=datetime.date(2008, 3, 3),
            publisher_id=self.p2.id,
            rating=3.0
        )
        # Different DB backends return different types for the extra select computation
        self.assertIn(obj.manufacture_cost, (11.545, Decimal('11.545')))

        # Values queries can be combined with annotate and extra
        obj = Book.objects.annotate(mean_auth_age=Avg('authors__age')).extra(
            select={'manufacture_cost': 'price * .5'}).values().get(pk=self.b2.pk)
        manufacture_cost = obj['manufacture_cost']
        self.assertIn(manufacture_cost, (11.545, Decimal('11.545')))
        del obj['manufacture_cost']
        self.assertEqual(obj, {
            'id': self.b2.id,
            'contact_id': self.a3.id,
            'isbn': '067232959',
            'mean_auth_age': 45.0,
            'name': 'Sams Teach Yourself Django in 24 Hours',
            'pages': 528,
            'price': Decimal('23.09'),
            'pubdate': datetime.date(2008, 3, 3),
            'publisher_id': self.p2.id,
            'rating': 3.0,
        })

        # The order of the (empty) values, annotate and extra clauses doesn't
        # matter
        obj = Book.objects.values().annotate(mean_auth_age=Avg('authors__age')).extra(
            select={'manufacture_cost': 'price * .5'}).get(pk=self.b2.pk)
        manufacture_cost = obj['manufacture_cost']
        self.assertIn(manufacture_cost, (11.545, Decimal('11.545')))
        del obj['manufacture_cost']
        self.assertEqual(obj, {
            'id': self.b2.id,
            'contact_id': self.a3.id,
            'isbn': '067232959',
            'mean_auth_age': 45.0,
            'name': 'Sams Teach Yourself Django in 24 Hours',
            'pages': 528,
            'price': Decimal('23.09'),
            'pubdate': datetime.date(2008, 3, 3),
            'publisher_id': self.p2.id,
            'rating': 3.0
        })

        # If the annotation precedes the values clause, it won't be included
        # unless it is explicitly named
        obj = Book.objects.annotate(mean_auth_age=Avg('authors__age')).extra(
            select={'price_per_page': 'price / pages'}).values('name').get(pk=self.b1.pk)
        self.assertEqual(obj, {
            "name": 'The Definitive Guide to Django: Web Development Done Right',
        })

        obj = Book.objects.annotate(mean_auth_age=Avg('authors__age')).extra(
            select={'price_per_page': 'price / pages'}).values('name', 'mean_auth_age').get(pk=self.b1.pk)
        self.assertEqual(obj, {
            'mean_auth_age': 34.5,
            'name': 'The Definitive Guide to Django: Web Development Done Right',
        })

        # If an annotation isn't included in the values, it can still be used
        # in a filter
        qs = Book.objects.annotate(n_authors=Count('authors')).values('name').filter(n_authors__gt=2)
        self.assertSequenceEqual(
            qs, [
                {"name": 'Python Web Development with Django'}
            ],
        )

        # The annotations are added to values output if values() precedes
        # annotate()
        obj = Book.objects.values('name').annotate(mean_auth_age=Avg('authors__age')).extra(
            select={'price_per_page': 'price / pages'}).get(pk=self.b1.pk)
        self.assertEqual(obj, {
            'mean_auth_age': 34.5,
            'name': 'The Definitive Guide to Django: Web Development Done Right',
        })

        # All of the objects are getting counted (allow_nulls) and that values
        # respects the amount of objects
        self.assertEqual(
            len(Author.objects.annotate(Avg('friends__age')).values()),
            9
        )

        # Consecutive calls to annotate accumulate in the query
        qs = (
            Book.objects
            .values('price')
            .annotate(oldest=Max('authors__age'))
            .order_by('oldest', 'price')
            .annotate(Max('publisher__num_awards'))
        )
        self.assertSequenceEqual(
            qs, [
                {'price': Decimal("30"), 'oldest': 35, 'publisher__num_awards__max': 3},
                {'price': Decimal("29.69"), 'oldest': 37, 'publisher__num_awards__max': 7},
                {'price': Decimal("23.09"), 'oldest': 45, 'publisher__num_awards__max': 1},
                {'price': Decimal("75"), 'oldest': 57, 'publisher__num_awards__max': 9},
                {'price': Decimal("82.8"), 'oldest': 57, 'publisher__num_awards__max': 7}
            ],
        )

    def test_aggregate_annotation(self):
        # Aggregates can be composed over annotations.
        # The return type is derived from the composed aggregate
        vals = (
            Book.objects
            .all()
            .annotate(num_authors=Count('authors__id'))
            .aggregate(Max('pages'), Max('price'), Sum('num_authors'), Avg('num_authors'))
        )
        self.assertEqual(vals, {
            'num_authors__sum': 10,
            'num_authors__avg': Approximate(1.666, places=2),
            'pages__max': 1132,
            'price__max': Decimal("82.80")
        })

        # Regression for #15624 - Missing SELECT columns when using values, annotate
        # and aggregate in a single query
        self.assertEqual(
            Book.objects.annotate(c=Count('authors')).values('c').aggregate(Max('c')),
            {'c__max': 3}
        )

    def test_decimal_aggregate_annotation_filter(self):
        """
        Filtering on an aggregate annotation with Decimal values should work.
        Requires special handling on SQLite (#18247).
        """
        self.assertEqual(
            len(Author.objects.annotate(sum=Sum('book_contact_set__price')).filter(sum__gt=Decimal(40))),
            1
        )
        self.assertEqual(
            len(Author.objects.annotate(sum=Sum('book_contact_set__price')).filter(sum__lte=Decimal(40))),
            4
        )

    def test_field_error(self):
        # Bad field requests in aggregates are caught and reported
        with self.assertRaises(FieldError):
            Book.objects.all().aggregate(num_authors=Count('foo'))

        with self.assertRaises(FieldError):
            Book.objects.all().annotate(num_authors=Count('foo'))

        with self.assertRaises(FieldError):
            Book.objects.all().annotate(num_authors=Count('authors__id')).aggregate(Max('foo'))

    def test_more(self):
        # Old-style count aggregations can be mixed with new-style
        self.assertEqual(
            Book.objects.annotate(num_authors=Count('authors')).count(),
            6
        )

        # Non-ordinal, non-computed Aggregates over annotations correctly
        # inherit the annotation's internal type if the annotation is ordinal
        # or computed
        vals = Book.objects.annotate(num_authors=Count('authors')).aggregate(Max('num_authors'))
        self.assertEqual(
            vals,
            {'num_authors__max': 3}
        )

        vals = Publisher.objects.annotate(avg_price=Avg('book__price')).aggregate(Max('avg_price'))
        self.assertEqual(
            vals,
            {'avg_price__max': 75.0}
        )

        # Aliases are quoted to protected aliases that might be reserved names
        vals = Book.objects.aggregate(number=Max('pages'), select=Max('pages'))
        self.assertEqual(
            vals,
            {'number': 1132, 'select': 1132}
        )

        # Regression for #10064: select_related() plays nice with aggregates
        obj = Book.objects.select_related('publisher').annotate(
            num_authors=Count('authors')).values().get(isbn='013790395')
        self.assertEqual(obj, {
            'contact_id': self.a8.id,
            'id': self.b5.id,
            'isbn': '013790395',
            'name': 'Artificial Intelligence: A Modern Approach',
            'num_authors': 2,
            'pages': 1132,
            'price': Decimal("82.8"),
            'pubdate': datetime.date(1995, 1, 15),
            'publisher_id': self.p3.id,
            'rating': 4.0,
        })

        # Regression for #10010: exclude on an aggregate field is correctly
        # negated
        self.assertEqual(
            len(Book.objects.annotate(num_authors=Count('authors'))),
            6
        )
        self.assertEqual(
            len(Book.objects.annotate(num_authors=Count('authors')).filter(num_authors__gt=2)),
            1
        )
        self.assertEqual(
            len(Book.objects.annotate(num_authors=Count('authors')).exclude(num_authors__gt=2)),
            5
        )

        self.assertEqual(
            len(
                Book.objects
                .annotate(num_authors=Count('authors'))
                .filter(num_authors__lt=3)
                .exclude(num_authors__lt=2)
            ),
            2
        )
        self.assertEqual(
            len(
                Book.objects
                .annotate(num_authors=Count('authors'))
                .exclude(num_authors__lt=2)
                .filter(num_authors__lt=3)
            ),
            2
        )

    def test_aggregate_fexpr(self):
        # Aggregates can be used with F() expressions
        # ... where the F() is pushed into the HAVING clause
        qs = (
            Publisher.objects
            .annotate(num_books=Count('book'))
            .filter(num_books__lt=F('num_awards') / 2)
            .order_by('name')
            .values('name', 'num_books', 'num_awards')
        )
        self.assertSequenceEqual(
            qs, [
                {'num_books': 1, 'name': 'Morgan Kaufmann', 'num_awards': 9},
                {'num_books': 2, 'name': 'Prentice Hall', 'num_awards': 7}
            ],
        )

        qs = (
            Publisher.objects
            .annotate(num_books=Count('book'))
            .exclude(num_books__lt=F('num_awards') / 2)
            .order_by('name')
            .values('name', 'num_books', 'num_awards')
        )
        self.assertSequenceEqual(
            qs, [
                {'num_books': 2, 'name': 'Apress', 'num_awards': 3},
                {'num_books': 0, 'name': "Jonno's House of Books", 'num_awards': 0},
                {'num_books': 1, 'name': 'Sams', 'num_awards': 1}
            ],
        )

        # ... and where the F() references an aggregate
        qs = (
            Publisher.objects
            .annotate(num_books=Count('book'))
            .filter(num_awards__gt=2 * F('num_books'))
            .order_by('name')
            .values('name', 'num_books', 'num_awards')
        )
        self.assertSequenceEqual(
            qs, [
                {'num_books': 1, 'name': 'Morgan Kaufmann', 'num_awards': 9},
                {'num_books': 2, 'name': 'Prentice Hall', 'num_awards': 7}
            ],
        )

        qs = (
            Publisher.objects
            .annotate(num_books=Count('book'))
            .exclude(num_books__lt=F('num_awards') / 2)
            .order_by('name')
            .values('name', 'num_books', 'num_awards')
        )
        self.assertSequenceEqual(
            qs, [
                {'num_books': 2, 'name': 'Apress', 'num_awards': 3},
                {'num_books': 0, 'name': "Jonno's House of Books", 'num_awards': 0},
                {'num_books': 1, 'name': 'Sams', 'num_awards': 1}
            ],
        )

    def test_db_col_table(self):
        # Tests on fields with non-default table and column names.
        qs = (
            Clues.objects
            .values('EntryID__Entry')
            .annotate(Appearances=Count('EntryID'), Distinct_Clues=Count('Clue', distinct=True))
        )
        self.assertQuerysetEqual(qs, [])

        qs = Entries.objects.annotate(clue_count=Count('clues__ID'))
        self.assertQuerysetEqual(qs, [])

    def test_boolean_conversion(self):
        # Aggregates mixed up ordering of columns for backend's convert_values
        # method. Refs #21126.
        e = Entries.objects.create(Entry='foo')
        c = Clues.objects.create(EntryID=e, Clue='bar')
        qs = Clues.objects.select_related('EntryID').annotate(Count('ID'))
        self.assertSequenceEqual(qs, [c])
        self.assertEqual(qs[0].EntryID, e)
        self.assertIs(qs[0].EntryID.Exclude, False)

    def test_empty(self):
        # Regression for #10089: Check handling of empty result sets with
        # aggregates
        self.assertEqual(
            Book.objects.filter(id__in=[]).count(),
            0
        )

        vals = (
            Book.objects
            .filter(id__in=[])
            .aggregate(
                num_authors=Count('authors'),
                avg_authors=Avg('authors'),
                max_authors=Max('authors'),
                max_price=Max('price'),
                max_rating=Max('rating'),
            )
        )
        self.assertEqual(
            vals,
            {'max_authors': None, 'max_rating': None, 'num_authors': 0, 'avg_authors': None, 'max_price': None}
        )

        qs = (
            Publisher.objects
            .filter(name="Jonno's House of Books")
            .annotate(
                num_authors=Count('book__authors'),
                avg_authors=Avg('book__authors'),
                max_authors=Max('book__authors'),
                max_price=Max('book__price'),
                max_rating=Max('book__rating'),
            ).values()
        )
        self.assertSequenceEqual(
            qs,
            [{
                'max_authors': None,
                'name': "Jonno's House of Books",
                'num_awards': 0,
                'max_price': None,
                'num_authors': 0,
                'max_rating': None,
                'id': self.p5.id,
                'avg_authors': None,
            }],
        )

    def test_more_more(self):
        # Regression for #10113 - Fields mentioned in order_by() must be
        # included in the GROUP BY. This only becomes a problem when the
        # order_by introduces a new join.
        self.assertQuerysetEqual(
            Book.objects.annotate(num_authors=Count('authors')).order_by('publisher__name', 'name'), [
                "Practical Django Projects",
                "The Definitive Guide to Django: Web Development Done Right",
                "Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp",
                "Artificial Intelligence: A Modern Approach",
                "Python Web Development with Django",
                "Sams Teach Yourself Django in 24 Hours",
            ],
            lambda b: b.name
        )

        # Regression for #10127 - Empty select_related() works with annotate
        qs = Book.objects.filter(rating__lt=4.5).select_related().annotate(Avg('authors__age'))
        self.assertQuerysetEqual(
            qs,
            [
                ('Artificial Intelligence: A Modern Approach', 51.5, 'Prentice Hall', 'Peter Norvig'),
                ('Practical Django Projects', 29.0, 'Apress', 'James Bennett'),
                (
                    'Python Web Development with Django',
                    Approximate(30.333, places=2),
                    'Prentice Hall',
                    'Jeffrey Forcier',
                ),
                ('Sams Teach Yourself Django in 24 Hours', 45.0, 'Sams', 'Brad Dayley')
            ],
            lambda b: (b.name, b.authors__age__avg, b.publisher.name, b.contact.name)
        )

        # Regression for #10132 - If the values() clause only mentioned extra
        # (select=) columns, those columns are used for grouping
        qs = Book.objects.extra(select={'pub': 'publisher_id'}).values('pub').annotate(Count('id')).order_by('pub')
        self.assertSequenceEqual(
            qs, [
                {'pub': self.b1.id, 'id__count': 2},
                {'pub': self.b2.id, 'id__count': 1},
                {'pub': self.b3.id, 'id__count': 2},
                {'pub': self.b4.id, 'id__count': 1}
            ],
        )

        qs = (
            Book.objects
            .extra(select={'pub': 'publisher_id', 'foo': 'pages'})
            .values('pub')
            .annotate(Count('id'))
            .order_by('pub')
        )
        self.assertSequenceEqual(
            qs, [
                {'pub': self.p1.id, 'id__count': 2},
                {'pub': self.p2.id, 'id__count': 1},
                {'pub': self.p3.id, 'id__count': 2},
                {'pub': self.p4.id, 'id__count': 1}
            ],
        )

        # Regression for #10182 - Queries with aggregate calls are correctly
        # realiased when used in a subquery
        ids = (
            Book.objects
            .filter(pages__gt=100)
            .annotate(n_authors=Count('authors'))
            .filter(n_authors__gt=2)
            .order_by('n_authors')
        )
        self.assertQuerysetEqual(
            Book.objects.filter(id__in=ids), [
                "Python Web Development with Django",
            ],
            lambda b: b.name
        )

        # Regression for #15709 - Ensure each group_by field only exists once
        # per query
        qstr = str(Book.objects.values('publisher').annotate(max_pages=Max('pages')).order_by().query)
        # There is just one GROUP BY clause (zero commas means at most one clause).
        self.assertEqual(qstr[qstr.index('GROUP BY'):].count(', '), 0)

    def test_duplicate_alias(self):
        # Regression for #11256 - duplicating a default alias raises ValueError.
        with self.assertRaises(ValueError):
            Book.objects.all().annotate(Avg('authors__age'), authors__age__avg=Avg('authors__age'))

    def test_field_name_conflict(self):
        # Regression for #11256 - providing an aggregate name
        # that conflicts with a field name on the model raises ValueError
        with self.assertRaises(ValueError):
            Author.objects.annotate(age=Avg('friends__age'))

    def test_m2m_name_conflict(self):
        # Regression for #11256 - providing an aggregate name
        # that conflicts with an m2m name on the model raises ValueError
        with self.assertRaises(ValueError):
            Author.objects.annotate(friends=Count('friends'))

    def test_values_queryset_non_conflict(self):
        # Regression for #14707 -- If you're using a values query set, some potential conflicts are avoided.

        # age is a field on Author, so it shouldn't be allowed as an aggregate.
        # But age isn't included in values(), so it is.
        results = Author.objects.values('name').annotate(age=Count('book_contact_set')).order_by('name')
        self.assertEqual(len(results), 9)
        self.assertEqual(results[0]['name'], 'Adrian Holovaty')
        self.assertEqual(results[0]['age'], 1)

        # Same problem, but aggregating over m2m fields
        results = Author.objects.values('name').annotate(age=Avg('friends__age')).order_by('name')
        self.assertEqual(len(results), 9)
        self.assertEqual(results[0]['name'], 'Adrian Holovaty')
        self.assertEqual(results[0]['age'], 32.0)

        # Same problem, but colliding with an m2m field
        results = Author.objects.values('name').annotate(friends=Count('friends')).order_by('name')
        self.assertEqual(len(results), 9)
        self.assertEqual(results[0]['name'], 'Adrian Holovaty')
        self.assertEqual(results[0]['friends'], 2)

    def test_reverse_relation_name_conflict(self):
        # Regression for #11256 - providing an aggregate name
        # that conflicts with a reverse-related name on the model raises ValueError
        with self.assertRaises(ValueError):
            Author.objects.annotate(book_contact_set=Avg('friends__age'))

    def test_pickle(self):
        # Regression for #10197 -- Queries with aggregates can be pickled.
        # First check that pickling is possible at all. No crash = success
        qs = Book.objects.annotate(num_authors=Count('authors'))
        pickle.dumps(qs)

        # Then check that the round trip works.
        query = qs.query.get_compiler(qs.db).as_sql()[0]
        qs2 = pickle.loads(pickle.dumps(qs))
        self.assertEqual(
            qs2.query.get_compiler(qs2.db).as_sql()[0],
            query,
        )

    def test_more_more_more(self):
        # Regression for #10199 - Aggregate calls clone the original query so
        # the original query can still be used
        books = Book.objects.all()
        books.aggregate(Avg("authors__age"))
        self.assertQuerysetEqual(
            books.all(), [
                'Artificial Intelligence: A Modern Approach',
                'Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp',
                'Practical Django Projects',
                'Python Web Development with Django',
                'Sams Teach Yourself Django in 24 Hours',
                'The Definitive Guide to Django: Web Development Done Right'
            ],
            lambda b: b.name
        )

        # Regression for #10248 - Annotations work with dates()
        qs = Book.objects.annotate(num_authors=Count('authors')).filter(num_authors=2).dates('pubdate', 'day')
        self.assertSequenceEqual(
            qs, [
                datetime.date(1995, 1, 15),
                datetime.date(2007, 12, 6),
            ],
        )

        # Regression for #10290 - extra selects with parameters can be used for
        # grouping.
        qs = (
            Book.objects
            .annotate(mean_auth_age=Avg('authors__age'))
            .extra(select={'sheets': '(pages + %s) / %s'}, select_params=[1, 2])
            .order_by('sheets')
            .values('sheets')
        )
        self.assertQuerysetEqual(
            qs, [
                150,
                175,
                224,
                264,
                473,
                566
            ],
            lambda b: int(b["sheets"])
        )

        # Regression for 10425 - annotations don't get in the way of a count()
        # clause
        self.assertEqual(
            Book.objects.values('publisher').annotate(Count('publisher')).count(),
            4
        )
        self.assertEqual(
            Book.objects.annotate(Count('publisher')).values('publisher').count(),
            6
        )

        # Note: intentionally no order_by(), that case needs tests, too.
        publishers = Publisher.objects.filter(id__in=[1, 2])
        self.assertEqual(
            sorted(p.name for p in publishers),
            [
                "Apress",
                "Sams"
            ]
        )

        publishers = publishers.annotate(n_books=Count("book"))
        sorted_publishers = sorted(publishers, key=lambda x: x.name)
        self.assertEqual(
            sorted_publishers[0].n_books,
            2
        )
        self.assertEqual(
            sorted_publishers[1].n_books,
            1
        )

        self.assertEqual(
            sorted(p.name for p in publishers),
            [
                "Apress",
                "Sams"
            ]
        )

        books = Book.objects.filter(publisher__in=publishers)
        self.assertQuerysetEqual(
            books, [
                "Practical Django Projects",
                "Sams Teach Yourself Django in 24 Hours",
                "The Definitive Guide to Django: Web Development Done Right",
            ],
            lambda b: b.name
        )
        self.assertEqual(
            sorted(p.name for p in publishers),
            [
                "Apress",
                "Sams"
            ]
        )

        # Regression for 10666 - inherited fields work with annotations and
        # aggregations
        self.assertEqual(
            HardbackBook.objects.aggregate(n_pages=Sum('book_ptr__pages')),
            {'n_pages': 2078}
        )

        self.assertEqual(
            HardbackBook.objects.aggregate(n_pages=Sum('pages')),
            {'n_pages': 2078},
        )

        qs = HardbackBook.objects.annotate(n_authors=Count('book_ptr__authors')).values('name', 'n_authors')
        self.assertSequenceEqual(
            qs,
            [
                {'n_authors': 2, 'name': 'Artificial Intelligence: A Modern Approach'},
                {
                    'n_authors': 1,
                    'name': 'Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp'
                }
            ],
        )

        qs = HardbackBook.objects.annotate(n_authors=Count('authors')).values('name', 'n_authors')
        self.assertSequenceEqual(
            qs,
            [
                {'n_authors': 2, 'name': 'Artificial Intelligence: A Modern Approach'},
                {
                    'n_authors': 1,
                    'name': 'Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp'
                }
            ],
        )

        # Regression for #10766 - Shouldn't be able to reference an aggregate
        # fields in an aggregate() call.
        with self.assertRaises(FieldError):
            Book.objects.annotate(mean_age=Avg('authors__age')).annotate(Avg('mean_age'))

    def test_empty_filter_count(self):
        self.assertEqual(
            Author.objects.filter(id__in=[]).annotate(Count("friends")).count(),
            0
        )

    def test_empty_filter_aggregate(self):
        self.assertEqual(
            Author.objects.filter(id__in=[]).annotate(Count("friends")).aggregate(Count("pk")),
            {"pk__count": None}
        )

    def test_none_call_before_aggregate(self):
        # Regression for #11789
        self.assertEqual(
            Author.objects.none().aggregate(Avg('age')),
            {'age__avg': None}
        )

    def test_annotate_and_join(self):
        self.assertEqual(
            Author.objects.annotate(c=Count("friends__name")).exclude(friends__name="Joe").count(),
            Author.objects.count()
        )

    def test_f_expression_annotation(self):
        # Books with less than 200 pages per author.
        qs = Book.objects.values("name").annotate(
            n_authors=Count("authors")
        ).filter(
            pages__lt=F("n_authors") * 200
        ).values_list("pk")
        self.assertQuerysetEqual(
            Book.objects.filter(pk__in=qs), [
                "Python Web Development with Django"
            ],
            attrgetter("name")
        )

    def test_values_annotate_values(self):
        qs = Book.objects.values("name").annotate(
            n_authors=Count("authors")
        ).values_list("pk", flat=True)
        self.assertEqual(list(qs), list(Book.objects.values_list("pk", flat=True)))

    def test_having_group_by(self):
        # When a field occurs on the LHS of a HAVING clause that it
        # appears correctly in the GROUP BY clause
        qs = Book.objects.values_list("name").annotate(
            n_authors=Count("authors")
        ).filter(
            pages__gt=F("n_authors")
        ).values_list("name", flat=True)
        # Results should be the same, all Books have more pages than authors
        self.assertEqual(
            list(qs), list(Book.objects.values_list("name", flat=True))
        )

    def test_values_list_annotation_args_ordering(self):
        """
        Annotate *args ordering should be preserved in values_list results.
        **kwargs comes after *args.
        Regression test for #23659.
        """
        books = Book.objects.values_list("publisher__name").annotate(
            Count("id"), Avg("price"), Avg("authors__age"), avg_pgs=Avg("pages")
        ).order_by("-publisher__name")
        self.assertEqual(books[0], ('Sams', 1, 23.09, 45.0, 528.0))

    def test_annotation_disjunction(self):
        qs = Book.objects.annotate(n_authors=Count("authors")).filter(
            Q(n_authors=2) | Q(name="Python Web Development with Django")
        )
        self.assertQuerysetEqual(
            qs, [
                "Artificial Intelligence: A Modern Approach",
                "Python Web Development with Django",
                "The Definitive Guide to Django: Web Development Done Right",
            ],
            attrgetter("name")
        )

        qs = (
            Book.objects
            .annotate(n_authors=Count("authors"))
            .filter(
                Q(name="The Definitive Guide to Django: Web Development Done Right") |
                (Q(name="Artificial Intelligence: A Modern Approach") & Q(n_authors=3))
            )
        )
        self.assertQuerysetEqual(
            qs,
            [
                "The Definitive Guide to Django: Web Development Done Right",
            ],
            attrgetter("name")
        )

        qs = Publisher.objects.annotate(
            rating_sum=Sum("book__rating"),
            book_count=Count("book")
        ).filter(
            Q(rating_sum__gt=5.5) | Q(rating_sum__isnull=True)
        ).order_by('pk')
        self.assertQuerysetEqual(
            qs, [
                "Apress",
                "Prentice Hall",
                "Jonno's House of Books",
            ],
            attrgetter("name")
        )

        qs = Publisher.objects.annotate(
            rating_sum=Sum("book__rating"),
            book_count=Count("book")
        ).filter(
            Q(rating_sum__gt=F("book_count")) | Q(rating_sum=None)
        ).order_by("num_awards")
        self.assertQuerysetEqual(
            qs, [
                "Jonno's House of Books",
                "Sams",
                "Apress",
                "Prentice Hall",
                "Morgan Kaufmann"
            ],
            attrgetter("name")
        )

    def test_quoting_aggregate_order_by(self):
        qs = Book.objects.filter(
            name="Python Web Development with Django"
        ).annotate(
            authorCount=Count("authors")
        ).order_by("authorCount")
        self.assertQuerysetEqual(
            qs, [
                ("Python Web Development with Django", 3),
            ],
            lambda b: (b.name, b.authorCount)
        )

    @skipUnlessDBFeature('supports_stddev')
    def test_stddev(self):
        self.assertEqual(
            Book.objects.aggregate(StdDev('pages')),
            {'pages__stddev': Approximate(311.46, 1)}
        )

        self.assertEqual(
            Book.objects.aggregate(StdDev('rating')),
            {'rating__stddev': Approximate(0.60, 1)}
        )

        self.assertEqual(
            Book.objects.aggregate(StdDev('price')),
            {'price__stddev': Approximate(24.16, 2)}
        )

        self.assertEqual(
            Book.objects.aggregate(StdDev('pages', sample=True)),
            {'pages__stddev': Approximate(341.19, 2)}
        )

        self.assertEqual(
            Book.objects.aggregate(StdDev('rating', sample=True)),
            {'rating__stddev': Approximate(0.66, 2)}
        )

        self.assertEqual(
            Book.objects.aggregate(StdDev('price', sample=True)),
            {'price__stddev': Approximate(26.46, 1)}
        )

        self.assertEqual(
            Book.objects.aggregate(Variance('pages')),
            {'pages__variance': Approximate(97010.80, 1)}
        )

        self.assertEqual(
            Book.objects.aggregate(Variance('rating')),
            {'rating__variance': Approximate(0.36, 1)}
        )

        self.assertEqual(
            Book.objects.aggregate(Variance('price')),
            {'price__variance': Approximate(583.77, 1)}
        )

        self.assertEqual(
            Book.objects.aggregate(Variance('pages', sample=True)),
            {'pages__variance': Approximate(116412.96, 1)}
        )

        self.assertEqual(
            Book.objects.aggregate(Variance('rating', sample=True)),
            {'rating__variance': Approximate(0.44, 2)}
        )

        self.assertEqual(
            Book.objects.aggregate(Variance('price', sample=True)),
            {'price__variance': Approximate(700.53, 2)}
        )

    def test_filtering_by_annotation_name(self):
        # Regression test for #14476

        # The name of the explicitly provided annotation name in this case
        # poses no problem
        qs = Author.objects.annotate(book_cnt=Count('book')).filter(book_cnt=2).order_by('name')
        self.assertQuerysetEqual(
            qs,
            ['Peter Norvig'],
            lambda b: b.name
        )
        # Neither in this case
        qs = Author.objects.annotate(book_count=Count('book')).filter(book_count=2).order_by('name')
        self.assertQuerysetEqual(
            qs,
            ['Peter Norvig'],
            lambda b: b.name
        )
        # This case used to fail because the ORM couldn't resolve the
        # automatically generated annotation name `book__count`
        qs = Author.objects.annotate(Count('book')).filter(book__count=2).order_by('name')
        self.assertQuerysetEqual(
            qs,
            ['Peter Norvig'],
            lambda b: b.name
        )
        # Referencing the auto-generated name in an aggregate() also works.
        self.assertEqual(
            Author.objects.annotate(Count('book')).aggregate(Max('book__count')),
            {'book__count__max': 2}
        )

    def test_annotate_joins(self):
        """
        The base table's join isn't promoted to LOUTER. This could
        cause the query generation to fail if there is an exclude() for fk-field
        in the query, too. Refs #19087.
        """
        qs = Book.objects.annotate(n=Count('pk'))
        self.assertIs(qs.query.alias_map['aggregation_regress_book'].join_type, None)
        # The query executes without problems.
        self.assertEqual(len(qs.exclude(publisher=-1)), 6)

    @skipUnlessAnyDBFeature('allows_group_by_pk', 'allows_group_by_selected_pks')
    def test_aggregate_duplicate_columns(self):
        # Regression test for #17144

        results = Author.objects.annotate(num_contacts=Count('book_contact_set'))

        # There should only be one GROUP BY clause, for the `id` column.
        # `name` and `age` should not be grouped on.
        _, _, group_by = results.query.get_compiler(using='default').pre_sql_setup()
        self.assertEqual(len(group_by), 1)
        self.assertIn('id', group_by[0][0])
        self.assertNotIn('name', group_by[0][0])
        self.assertNotIn('age', group_by[0][0])
        self.assertEqual(
            [(a.name, a.num_contacts) for a in results.order_by('name')],
            [
                ('Adrian Holovaty', 1),
                ('Brad Dayley', 1),
                ('Jacob Kaplan-Moss', 0),
                ('James Bennett', 1),
                ('Jeffrey Forcier', 1),
                ('Paul Bissex', 0),
                ('Peter Norvig', 2),
                ('Stuart Russell', 0),
                ('Wesley J. Chun', 0),
            ]
        )

    @skipUnlessAnyDBFeature('allows_group_by_pk', 'allows_group_by_selected_pks')
    def test_aggregate_duplicate_columns_only(self):
        # Works with only() too.
        results = Author.objects.only('id', 'name').annotate(num_contacts=Count('book_contact_set'))
        _, _, grouping = results.query.get_compiler(using='default').pre_sql_setup()
        self.assertEqual(len(grouping), 1)
        self.assertIn('id', grouping[0][0])
        self.assertNotIn('name', grouping[0][0])
        self.assertNotIn('age', grouping[0][0])
        self.assertEqual(
            [(a.name, a.num_contacts) for a in results.order_by('name')],
            [
                ('Adrian Holovaty', 1),
                ('Brad Dayley', 1),
                ('Jacob Kaplan-Moss', 0),
                ('James Bennett', 1),
                ('Jeffrey Forcier', 1),
                ('Paul Bissex', 0),
                ('Peter Norvig', 2),
                ('Stuart Russell', 0),
                ('Wesley J. Chun', 0),
            ]
        )

    @skipUnlessAnyDBFeature('allows_group_by_pk', 'allows_group_by_selected_pks')
    def test_aggregate_duplicate_columns_select_related(self):
        # And select_related()
        results = Book.objects.select_related('contact').annotate(
            num_authors=Count('authors'))
        _, _, grouping = results.query.get_compiler(using='default').pre_sql_setup()
        # In the case of `group_by_selected_pks` we also group by contact.id because of the select_related.
        self.assertEqual(len(grouping), 1 if connection.features.allows_group_by_pk else 2)
        self.assertIn('id', grouping[0][0])
        self.assertNotIn('name', grouping[0][0])
        self.assertNotIn('contact', grouping[0][0])
        self.assertEqual(
            [(b.name, b.num_authors) for b in results.order_by('name')],
            [
                ('Artificial Intelligence: A Modern Approach', 2),
                ('Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp', 1),
                ('Practical Django Projects', 1),
                ('Python Web Development with Django', 3),
                ('Sams Teach Yourself Django in 24 Hours', 1),
                ('The Definitive Guide to Django: Web Development Done Right', 2)
            ]
        )

    def test_reverse_join_trimming(self):
        qs = Author.objects.annotate(Count('book_contact_set__contact'))
        self.assertIn(' JOIN ', str(qs.query))

    def test_aggregation_with_generic_reverse_relation(self):
        """
        Regression test for #10870:  Aggregates with joins ignore extra
        filters provided by setup_joins

        tests aggregations with generic reverse relations
        """
        django_book = Book.objects.get(name='Practical Django Projects')
        ItemTag.objects.create(
            object_id=django_book.id, tag='intermediate',
            content_type=ContentType.objects.get_for_model(django_book),
        )
        ItemTag.objects.create(
            object_id=django_book.id, tag='django',
            content_type=ContentType.objects.get_for_model(django_book),
        )
        # Assign a tag to model with same PK as the book above. If the JOIN
        # used in aggregation doesn't have content type as part of the
        # condition the annotation will also count the 'hi mom' tag for b.
        wmpk = WithManualPK.objects.create(id=django_book.pk)
        ItemTag.objects.create(
            object_id=wmpk.id, tag='hi mom',
            content_type=ContentType.objects.get_for_model(wmpk),
        )
        ai_book = Book.objects.get(name__startswith='Paradigms of Artificial Intelligence')
        ItemTag.objects.create(
            object_id=ai_book.id, tag='intermediate',
            content_type=ContentType.objects.get_for_model(ai_book),
        )

        self.assertEqual(Book.objects.aggregate(Count('tags')), {'tags__count': 3})
        results = Book.objects.annotate(Count('tags')).order_by('-tags__count', 'name')
        self.assertEqual(
            [(b.name, b.tags__count) for b in results],
            [
                ('Practical Django Projects', 2),
                ('Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp', 1),
                ('Artificial Intelligence: A Modern Approach', 0),
                ('Python Web Development with Django', 0),
                ('Sams Teach Yourself Django in 24 Hours', 0),
                ('The Definitive Guide to Django: Web Development Done Right', 0)
            ]
        )

    def test_negated_aggregation(self):
        expected_results = Author.objects.exclude(
            pk__in=Author.objects.annotate(book_cnt=Count('book')).filter(book_cnt=2)
        ).order_by('name')
        expected_results = [a.name for a in expected_results]
        qs = Author.objects.annotate(book_cnt=Count('book')).exclude(
            Q(book_cnt=2), Q(book_cnt=2)).order_by('name')
        self.assertQuerysetEqual(
            qs,
            expected_results,
            lambda b: b.name
        )
        expected_results = Author.objects.exclude(
            pk__in=Author.objects.annotate(book_cnt=Count('book')).filter(book_cnt=2)
        ).order_by('name')
        expected_results = [a.name for a in expected_results]
        qs = Author.objects.annotate(book_cnt=Count('book')).exclude(Q(book_cnt=2) | Q(book_cnt=2)).order_by('name')
        self.assertQuerysetEqual(
            qs,
            expected_results,
            lambda b: b.name
        )

    def test_name_filters(self):
        qs = Author.objects.annotate(Count('book')).filter(
            Q(book__count__exact=2) | Q(name='Adrian Holovaty')
        ).order_by('name')
        self.assertQuerysetEqual(
            qs,
            ['Adrian Holovaty', 'Peter Norvig'],
            lambda b: b.name
        )

    def test_name_expressions(self):
        # Aggregates are spotted correctly from F objects.
        # Note that Adrian's age is 34 in the fixtures, and he has one book
        # so both conditions match one author.
        qs = Author.objects.annotate(Count('book')).filter(
            Q(name='Peter Norvig') | Q(age=F('book__count') + 33)
        ).order_by('name')
        self.assertQuerysetEqual(
            qs,
            ['Adrian Holovaty', 'Peter Norvig'],
            lambda b: b.name
        )

    def test_ticket_11293(self):
        q1 = Q(price__gt=50)
        q2 = Q(authors__count__gt=1)
        query = Book.objects.annotate(Count('authors')).filter(
            q1 | q2).order_by('pk')
        self.assertQuerysetEqual(
            query, [1, 4, 5, 6],
            lambda b: b.pk)

    def test_ticket_11293_q_immutable(self):
        """
        Splitting a q object to parts for where/having doesn't alter
        the original q-object.
        """
        q1 = Q(isbn='')
        q2 = Q(authors__count__gt=1)
        query = Book.objects.annotate(Count('authors'))
        query.filter(q1 | q2)
        self.assertEqual(len(q2.children), 1)

    def test_fobj_group_by(self):
        """
        An F() object referring to related column works correctly in group by.
        """
        qs = Book.objects.annotate(
            account=Count('authors')
        ).filter(
            account=F('publisher__num_awards')
        )
        self.assertQuerysetEqual(
            qs, ['Sams Teach Yourself Django in 24 Hours'],
            lambda b: b.name)

    def test_annotate_reserved_word(self):
        """
        Regression #18333 - Ensure annotated column name is properly quoted.
        """
        vals = Book.objects.annotate(select=Count('authors__id')).aggregate(Sum('select'), Avg('select'))
        self.assertEqual(vals, {
            'select__sum': 10,
            'select__avg': Approximate(1.666, places=2),
        })

    def test_annotate_on_relation(self):
        book = Book.objects.annotate(avg_price=Avg('price'), publisher_name=F('publisher__name')).get(pk=self.b1.pk)
        self.assertEqual(book.avg_price, 30.00)
        self.assertEqual(book.publisher_name, "Apress")

    def test_aggregate_on_relation(self):
        # A query with an existing annotation aggregation on a relation should
        # succeed.
        qs = Book.objects.annotate(avg_price=Avg('price')).aggregate(
            publisher_awards=Sum('publisher__num_awards')
        )
        self.assertEqual(qs['publisher_awards'], 30)

    def test_annotate_distinct_aggregate(self):
        # There are three books with rating of 4.0 and two of the books have
        # the same price. Hence, the distinct removes one rating of 4.0
        # from the results.
        vals1 = Book.objects.values('rating', 'price').distinct().aggregate(result=Sum('rating'))
        vals2 = Book.objects.aggregate(result=Sum('rating') - Value(4.0))
        self.assertEqual(vals1, vals2)


class JoinPromotionTests(TestCase):
    def test_ticket_21150(self):
        b = Bravo.objects.create()
        c = Charlie.objects.create(bravo=b)
        qs = Charlie.objects.select_related('alfa').annotate(Count('bravo__charlie'))
        self.assertSequenceEqual(qs, [c])
        self.assertIs(qs[0].alfa, None)
        a = Alfa.objects.create()
        c.alfa = a
        c.save()
        # Force re-evaluation
        qs = qs.all()
        self.assertSequenceEqual(qs, [c])
        self.assertEqual(qs[0].alfa, a)

    def test_existing_join_not_promoted(self):
        # No promotion for existing joins
        qs = Charlie.objects.filter(alfa__name__isnull=False).annotate(Count('alfa__name'))
        self.assertIn(' INNER JOIN ', str(qs.query))
        # Also, the existing join is unpromoted when doing filtering for already
        # promoted join.
        qs = Charlie.objects.annotate(Count('alfa__name')).filter(alfa__name__isnull=False)
        self.assertIn(' INNER JOIN ', str(qs.query))
        # But, as the join is nullable first use by annotate will be LOUTER
        qs = Charlie.objects.annotate(Count('alfa__name'))
        self.assertIn(' LEFT OUTER JOIN ', str(qs.query))

    def test_non_nullable_fk_not_promoted(self):
        qs = Book.objects.annotate(Count('contact__name'))
        self.assertIn(' INNER JOIN ', str(qs.query))


class SelfReferentialFKTests(TestCase):
    def test_ticket_24748(self):
        t1 = SelfRefFK.objects.create(name='t1')
        SelfRefFK.objects.create(name='t2', parent=t1)
        SelfRefFK.objects.create(name='t3', parent=t1)
        self.assertQuerysetEqual(
            SelfRefFK.objects.annotate(num_children=Count('children')).order_by('name'),
            [('t1', 2), ('t2', 0), ('t3', 0)],
            lambda x: (x.name, x.num_children)
        )