django/tests/aggregation/tests.py

from __future__ import unicode_literals

import datetime
from decimal import Decimal
import re
import warnings

from django.core.exceptions import FieldError
from django.db import connection
from django.db.models import (
    Avg, Sum, Count, Max, Min,
    Aggregate, F, Value, Func,
    IntegerField, FloatField, DecimalField)
with warnings.catch_warnings(record=True) as w:
    warnings.simplefilter("always")
    from django.db.models.sql import aggregates as sql_aggregates
from django.test import TestCase
from django.test.utils import Approximate
from django.test.utils import CaptureQueriesContext
from django.utils import six, timezone
from django.utils.deprecation import RemovedInDjango20Warning

from .models import Author, Publisher, Book, Store


class BaseAggregateTestCase(TestCase):
    fixtures = ["aggregation.json"]

    def test_empty_aggregate(self):
        self.assertEqual(Author.objects.all().aggregate(), {})

    def test_single_aggregate(self):
        vals = Author.objects.aggregate(Avg("age"))
        self.assertEqual(vals, {"age__avg": Approximate(37.4, places=1)})

    def test_multiple_aggregates(self):
        vals = Author.objects.aggregate(Sum("age"), Avg("age"))
        self.assertEqual(vals, {"age__sum": 337, "age__avg": Approximate(37.4, places=1)})

    def test_filter_aggregate(self):
        vals = Author.objects.filter(age__gt=29).aggregate(Sum("age"))
        self.assertEqual(len(vals), 1)
        self.assertEqual(vals["age__sum"], 254)

    def test_related_aggregate(self):
        vals = Author.objects.aggregate(Avg("friends__age"))
        self.assertEqual(len(vals), 1)
        self.assertAlmostEqual(vals["friends__age__avg"], 34.07, places=2)

        vals = Book.objects.filter(rating__lt=4.5).aggregate(Avg("authors__age"))
        self.assertEqual(len(vals), 1)
        self.assertAlmostEqual(vals["authors__age__avg"], 38.2857, places=2)

        vals = Author.objects.all().filter(name__contains="a").aggregate(Avg("book__rating"))
        self.assertEqual(len(vals), 1)
        self.assertEqual(vals["book__rating__avg"], 4.0)

        vals = Book.objects.aggregate(Sum("publisher__num_awards"))
        self.assertEqual(len(vals), 1)
        self.assertEqual(vals["publisher__num_awards__sum"], 30)

        vals = Publisher.objects.aggregate(Sum("book__price"))
        self.assertEqual(len(vals), 1)
        self.assertEqual(vals["book__price__sum"], Decimal("270.27"))

    def test_aggregate_multi_join(self):
        vals = Store.objects.aggregate(Max("books__authors__age"))
        self.assertEqual(len(vals), 1)
        self.assertEqual(vals["books__authors__age__max"], 57)

        vals = Author.objects.aggregate(Min("book__publisher__num_awards"))
        self.assertEqual(len(vals), 1)
        self.assertEqual(vals["book__publisher__num_awards__min"], 1)

    def test_aggregate_alias(self):
        vals = Store.objects.filter(name="Amazon.com").aggregate(amazon_mean=Avg("books__rating"))
        self.assertEqual(len(vals), 1)
        self.assertAlmostEqual(vals["amazon_mean"], 4.08, places=2)

    def test_annotate_basic(self):
        self.assertQuerysetEqual(
            Book.objects.annotate().order_by('pk'), [
                "The Definitive Guide to Django: Web Development Done Right",
                "Sams Teach Yourself Django in 24 Hours",
                "Practical Django Projects",
                "Python Web Development with Django",
                "Artificial Intelligence: A Modern Approach",
                "Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp"
            ],
            lambda b: b.name
        )

        books = Book.objects.annotate(mean_age=Avg("authors__age"))
        b = books.get(pk=1)
        self.assertEqual(
            b.name,
            'The Definitive Guide to Django: Web Development Done Right'
        )
        self.assertEqual(b.mean_age, 34.5)

    def test_annotate_defer(self):
        qs = Book.objects.annotate(
            page_sum=Sum("pages")).defer('name').filter(pk=1)

        rows = [
            (1, "159059725", 447, "The Definitive Guide to Django: Web Development Done Right")
        ]
        self.assertQuerysetEqual(
            qs.order_by('pk'), rows,
            lambda r: (r.id, r.isbn, r.page_sum, r.name)
        )

    def test_annotate_defer_select_related(self):
        qs = Book.objects.select_related('contact').annotate(
            page_sum=Sum("pages")).defer('name').filter(pk=1)

        rows = [
            (1, "159059725", 447, "Adrian Holovaty",
             "The Definitive Guide to Django: Web Development Done Right")
        ]
        self.assertQuerysetEqual(
            qs.order_by('pk'), rows,
            lambda r: (r.id, r.isbn, r.page_sum, r.contact.name, r.name)
        )

    def test_annotate_m2m(self):
        books = Book.objects.filter(rating__lt=4.5).annotate(Avg("authors__age")).order_by("name")
        self.assertQuerysetEqual(
            books, [
                ('Artificial Intelligence: A Modern Approach', 51.5),
                ('Practical Django Projects', 29.0),
                ('Python Web Development with Django', Approximate(30.3, places=1)),
                ('Sams Teach Yourself Django in 24 Hours', 45.0)
            ],
            lambda b: (b.name, b.authors__age__avg),
        )

        books = Book.objects.annotate(num_authors=Count("authors")).order_by("name")
        self.assertQuerysetEqual(
            books, [
                ('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)
            ],
            lambda b: (b.name, b.num_authors)
        )

    def test_backwards_m2m_annotate(self):
        authors = Author.objects.filter(name__contains="a").annotate(Avg("book__rating")).order_by("name")
        self.assertQuerysetEqual(
            authors, [
                ('Adrian Holovaty', 4.5),
                ('Brad Dayley', 3.0),
                ('Jacob Kaplan-Moss', 4.5),
                ('James Bennett', 4.0),
                ('Paul Bissex', 4.0),
                ('Stuart Russell', 4.0)
            ],
            lambda a: (a.name, a.book__rating__avg)
        )

        authors = Author.objects.annotate(num_books=Count("book")).order_by("name")
        self.assertQuerysetEqual(
            authors, [
                ('Adrian Holovaty', 1),
                ('Brad Dayley', 1),
                ('Jacob Kaplan-Moss', 1),
                ('James Bennett', 1),
                ('Jeffrey Forcier', 1),
                ('Paul Bissex', 1),
                ('Peter Norvig', 2),
                ('Stuart Russell', 1),
                ('Wesley J. Chun', 1)
            ],
            lambda a: (a.name, a.num_books)
        )

    def test_reverse_fkey_annotate(self):
        books = Book.objects.annotate(Sum("publisher__num_awards")).order_by("name")
        self.assertQuerysetEqual(
            books, [
                ('Artificial Intelligence: A Modern Approach', 7),
                ('Paradigms of Artificial Intelligence Programming: Case Studies in Common Lisp', 9),
                ('Practical Django Projects', 3),
                ('Python Web Development with Django', 7),
                ('Sams Teach Yourself Django in 24 Hours', 1),
                ('The Definitive Guide to Django: Web Development Done Right', 3)
            ],
            lambda b: (b.name, b.publisher__num_awards__sum)
        )

        publishers = Publisher.objects.annotate(Sum("book__price")).order_by("name")
        self.assertQuerysetEqual(
            publishers, [
                ('Apress', Decimal("59.69")),
                ("Jonno's House of Books", None),
                ('Morgan Kaufmann', Decimal("75.00")),
                ('Prentice Hall', Decimal("112.49")),
                ('Sams', Decimal("23.09"))
            ],
            lambda p: (p.name, p.book__price__sum)
        )

    def test_annotate_values(self):
        books = list(Book.objects.filter(pk=1).annotate(mean_age=Avg("authors__age")).values())
        self.assertEqual(
            books, [
                {
                    "contact_id": 1,
                    "id": 1,
                    "isbn": "159059725",
                    "mean_age": 34.5,
                    "name": "The Definitive Guide to Django: Web Development Done Right",
                    "pages": 447,
                    "price": Approximate(Decimal("30")),
                    "pubdate": datetime.date(2007, 12, 6),
                    "publisher_id": 1,
                    "rating": 4.5,
                }
            ]
        )

        books = Book.objects.filter(pk=1).annotate(mean_age=Avg('authors__age')).values('pk', 'isbn', 'mean_age')
        self.assertEqual(
            list(books), [
                {
                    "pk": 1,
                    "isbn": "159059725",
                    "mean_age": 34.5,
                }
            ]
        )

        books = Book.objects.filter(pk=1).annotate(mean_age=Avg("authors__age")).values("name")
        self.assertEqual(
            list(books), [
                {
                    "name": "The Definitive Guide to Django: Web Development Done Right"
                }
            ]
        )

        books = Book.objects.filter(pk=1).values().annotate(mean_age=Avg('authors__age'))
        self.assertEqual(
            list(books), [
                {
                    "contact_id": 1,
                    "id": 1,
                    "isbn": "159059725",
                    "mean_age": 34.5,
                    "name": "The Definitive Guide to Django: Web Development Done Right",
                    "pages": 447,
                    "price": Approximate(Decimal("30")),
                    "pubdate": datetime.date(2007, 12, 6),
                    "publisher_id": 1,
                    "rating": 4.5,
                }
            ]
        )

        books = Book.objects.values("rating").annotate(n_authors=Count("authors__id"), mean_age=Avg("authors__age")).order_by("rating")
        self.assertEqual(
            list(books), [
                {
                    "rating": 3.0,
                    "n_authors": 1,
                    "mean_age": 45.0,
                },
                {
                    "rating": 4.0,
                    "n_authors": 6,
                    "mean_age": Approximate(37.16, places=1)
                },
                {
                    "rating": 4.5,
                    "n_authors": 2,
                    "mean_age": 34.5,
                },
                {
                    "rating": 5.0,
                    "n_authors": 1,
                    "mean_age": 57.0,
                }
            ]
        )

        authors = Author.objects.annotate(Avg("friends__age")).order_by("name")
        self.assertEqual(len(authors), 9)
        self.assertQuerysetEqual(
            authors, [
                ('Adrian Holovaty', 32.0),
                ('Brad Dayley', None),
                ('Jacob Kaplan-Moss', 29.5),
                ('James Bennett', 34.0),
                ('Jeffrey Forcier', 27.0),
                ('Paul Bissex', 31.0),
                ('Peter Norvig', 46.0),
                ('Stuart Russell', 57.0),
                ('Wesley J. Chun', Approximate(33.66, places=1))
            ],
            lambda a: (a.name, a.friends__age__avg)
        )

    def test_count(self):
        vals = Book.objects.aggregate(Count("rating"))
        self.assertEqual(vals, {"rating__count": 6})

        vals = Book.objects.aggregate(Count("rating", distinct=True))
        self.assertEqual(vals, {"rating__count": 4})

    def test_fkey_aggregate(self):
        explicit = list(Author.objects.annotate(Count('book__id')))
        implicit = list(Author.objects.annotate(Count('book')))
        self.assertEqual(explicit, implicit)

    def test_annotate_ordering(self):
        books = Book.objects.values('rating').annotate(oldest=Max('authors__age')).order_by('oldest', 'rating')
        self.assertEqual(
            list(books), [
                {
                    "rating": 4.5,
                    "oldest": 35,
                },
                {
                    "rating": 3.0,
                    "oldest": 45
                },
                {
                    "rating": 4.0,
                    "oldest": 57,
                },
                {
                    "rating": 5.0,
                    "oldest": 57,
                }
            ]
        )

        books = Book.objects.values("rating").annotate(oldest=Max("authors__age")).order_by("-oldest", "-rating")
        self.assertEqual(
            list(books), [
                {
                    "rating": 5.0,
                    "oldest": 57,
                },
                {
                    "rating": 4.0,
                    "oldest": 57,
                },
                {
                    "rating": 3.0,
                    "oldest": 45,
                },
                {
                    "rating": 4.5,
                    "oldest": 35,
                }
            ]
        )

    def test_aggregate_annotation(self):
        vals = Book.objects.annotate(num_authors=Count("authors__id")).aggregate(Avg("num_authors"))
        self.assertEqual(vals, {"num_authors__avg": Approximate(1.66, places=1)})

    def test_filtering(self):
        p = Publisher.objects.create(name='Expensive Publisher', num_awards=0)
        Book.objects.create(
            name='ExpensiveBook1',
            pages=1,
            isbn='111',
            rating=3.5,
            price=Decimal("1000"),
            publisher=p,
            contact_id=1,
            pubdate=datetime.date(2008, 12, 1)
        )
        Book.objects.create(
            name='ExpensiveBook2',
            pages=1,
            isbn='222',
            rating=4.0,
            price=Decimal("1000"),
            publisher=p,
            contact_id=1,
            pubdate=datetime.date(2008, 12, 2)
        )
        Book.objects.create(
            name='ExpensiveBook3',
            pages=1,
            isbn='333',
            rating=4.5,
            price=Decimal("35"),
            publisher=p,
            contact_id=1,
            pubdate=datetime.date(2008, 12, 3)
        )

        publishers = Publisher.objects.annotate(num_books=Count("book__id")).filter(num_books__gt=1).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
                "Prentice Hall",
                "Expensive Publisher",
            ],
            lambda p: p.name,
        )

        publishers = Publisher.objects.filter(book__price__lt=Decimal("40.0")).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
                "Apress",
                "Sams",
                "Prentice Hall",
                "Expensive Publisher",
            ],
            lambda p: p.name
        )

        publishers = Publisher.objects.annotate(num_books=Count("book__id")).filter(num_books__gt=1, book__price__lt=Decimal("40.0")).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
                "Prentice Hall",
                "Expensive Publisher",
            ],
            lambda p: p.name,
        )

        publishers = Publisher.objects.filter(book__price__lt=Decimal("40.0")).annotate(num_books=Count("book__id")).filter(num_books__gt=1).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
            ],
            lambda p: p.name
        )

        publishers = Publisher.objects.annotate(num_books=Count("book")).filter(num_books__range=[1, 3]).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
                "Sams",
                "Prentice Hall",
                "Morgan Kaufmann",
                "Expensive Publisher",
            ],
            lambda p: p.name
        )

        publishers = Publisher.objects.annotate(num_books=Count("book")).filter(num_books__range=[1, 2]).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
                "Sams",
                "Prentice Hall",
                "Morgan Kaufmann",
            ],
            lambda p: p.name
        )

        publishers = Publisher.objects.annotate(num_books=Count("book")).filter(num_books__in=[1, 3]).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Sams",
                "Morgan Kaufmann",
                "Expensive Publisher",
            ],
            lambda p: p.name,
        )

        publishers = Publisher.objects.annotate(num_books=Count("book")).filter(num_books__isnull=True)
        self.assertEqual(len(publishers), 0)

    def test_annotation(self):
        vals = Author.objects.filter(pk=1).aggregate(Count("friends__id"))
        self.assertEqual(vals, {"friends__id__count": 2})

        books = Book.objects.annotate(num_authors=Count("authors__name")).filter(num_authors__exact=2).order_by("pk")
        self.assertQuerysetEqual(
            books, [
                "The Definitive Guide to Django: Web Development Done Right",
                "Artificial Intelligence: A Modern Approach",
            ],
            lambda b: b.name
        )

        authors = Author.objects.annotate(num_friends=Count("friends__id", distinct=True)).filter(num_friends=0).order_by("pk")
        self.assertQuerysetEqual(
            authors, [
                "Brad Dayley",
            ],
            lambda a: a.name
        )

        publishers = Publisher.objects.annotate(num_books=Count("book__id")).filter(num_books__gt=1).order_by("pk")
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
                "Prentice Hall",
            ],
            lambda p: p.name
        )

        publishers = Publisher.objects.filter(book__price__lt=Decimal("40.0")).annotate(num_books=Count("book__id")).filter(num_books__gt=1)
        self.assertQuerysetEqual(
            publishers, [
                "Apress",
            ],
            lambda p: p.name
        )

        books = Book.objects.annotate(num_authors=Count("authors__id")).filter(authors__name__contains="Norvig", num_authors__gt=1)
        self.assertQuerysetEqual(
            books, [
                "Artificial Intelligence: A Modern Approach",
            ],
            lambda b: b.name
        )

    def test_more_aggregation(self):
        a = Author.objects.get(name__contains='Norvig')
        b = Book.objects.get(name__contains='Done Right')
        b.authors.add(a)
        b.save()

        vals = Book.objects.annotate(num_authors=Count("authors__id")).filter(authors__name__contains="Norvig", num_authors__gt=1).aggregate(Avg("rating"))
        self.assertEqual(vals, {"rating__avg": 4.25})

    def test_even_more_aggregate(self):
        publishers = Publisher.objects.annotate(earliest_book=Min("book__pubdate")).exclude(earliest_book=None).order_by("earliest_book").values()
        self.assertEqual(
            list(publishers), [
                {
                    'earliest_book': datetime.date(1991, 10, 15),
                    'num_awards': 9,
                    'id': 4,
                    'name': 'Morgan Kaufmann'
                },
                {
                    'earliest_book': datetime.date(1995, 1, 15),
                    'num_awards': 7,
                    'id': 3,
                    'name': 'Prentice Hall'
                },
                {
                    'earliest_book': datetime.date(2007, 12, 6),
                    'num_awards': 3,
                    'id': 1,
                    'name': 'Apress'
                },
                {
                    'earliest_book': datetime.date(2008, 3, 3),
                    'num_awards': 1,
                    'id': 2,
                    'name': 'Sams'
                }
            ]
        )

        vals = Store.objects.aggregate(Max("friday_night_closing"), Min("original_opening"))
        self.assertEqual(
            vals,
            {
                "friday_night_closing__max": datetime.time(23, 59, 59),
                "original_opening__min": datetime.datetime(1945, 4, 25, 16, 24, 14),
            }
        )

    def test_annotate_values_list(self):
        books = Book.objects.filter(pk=1).annotate(mean_age=Avg("authors__age")).values_list("pk", "isbn", "mean_age")
        self.assertEqual(
            list(books), [
                (1, "159059725", 34.5),
            ]
        )

        books = Book.objects.filter(pk=1).annotate(mean_age=Avg("authors__age")).values_list("isbn")
        self.assertEqual(
            list(books), [
                ('159059725',)
            ]
        )

        books = Book.objects.filter(pk=1).annotate(mean_age=Avg("authors__age")).values_list("mean_age")
        self.assertEqual(
            list(books), [
                (34.5,)
            ]
        )

        books = Book.objects.filter(pk=1).annotate(mean_age=Avg("authors__age")).values_list("mean_age", flat=True)
        self.assertEqual(list(books), [34.5])

        books = Book.objects.values_list("price").annotate(count=Count("price")).order_by("-count", "price")
        self.assertEqual(
            list(books), [
                (Decimal("29.69"), 2),
                (Decimal('23.09'), 1),
                (Decimal('30'), 1),
                (Decimal('75'), 1),
                (Decimal('82.8'), 1),
            ]
        )

    def test_dates_with_aggregation(self):
        """
        Test that .dates() returns a distinct set of dates when applied to a
        QuerySet with aggregation.

        Refs #18056. Previously, .dates() would return distinct (date_kind,
        aggregation) sets, in this case (year, num_authors), so 2008 would be
        returned twice because there are books from 2008 with a different
        number of authors.
        """
        dates = Book.objects.annotate(num_authors=Count("authors")).dates('pubdate', 'year')
        self.assertQuerysetEqual(
            dates, [
                "datetime.date(1991, 1, 1)",
                "datetime.date(1995, 1, 1)",
                "datetime.date(2007, 1, 1)",
                "datetime.date(2008, 1, 1)"
            ]
        )

    def test_values_aggregation(self):
        # Refs #20782
        max_rating = Book.objects.values('rating').aggregate(max_rating=Max('rating'))
        self.assertEqual(max_rating['max_rating'], 5)
        max_books_per_rating = Book.objects.values('rating').annotate(
            books_per_rating=Count('id')
        ).aggregate(Max('books_per_rating'))
        self.assertEqual(
            max_books_per_rating,
            {'books_per_rating__max': 3})

    def test_ticket17424(self):
        """
        Check that doing exclude() on a foreign model after annotate()
        doesn't crash.
        """
        all_books = list(Book.objects.values_list('pk', flat=True).order_by('pk'))
        annotated_books = Book.objects.order_by('pk').annotate(one=Count("id"))

        # The value doesn't matter, we just need any negative
        # constraint on a related model that's a noop.
        excluded_books = annotated_books.exclude(publisher__name="__UNLIKELY_VALUE__")

        # Try to generate query tree
        str(excluded_books.query)

        self.assertQuerysetEqual(excluded_books, all_books, lambda x: x.pk)

        # Check internal state
        self.assertIsNone(annotated_books.query.alias_map["aggregation_book"].join_type)
        self.assertIsNone(excluded_books.query.alias_map["aggregation_book"].join_type)

    def test_ticket12886(self):
        """
        Check that aggregation over sliced queryset works correctly.
        """
        qs = Book.objects.all().order_by('-rating')[0:3]
        vals = qs.aggregate(average_top3_rating=Avg('rating'))['average_top3_rating']
        self.assertAlmostEqual(vals, 4.5, places=2)

    def test_ticket11881(self):
        """
        Check that subqueries do not needlessly contain ORDER BY, SELECT FOR UPDATE
        or select_related() stuff.
        """
        qs = Book.objects.all().select_for_update().order_by(
            'pk').select_related('publisher').annotate(max_pk=Max('pk'))
        with CaptureQueriesContext(connection) as captured_queries:
            qs.aggregate(avg_pk=Avg('max_pk'))
            self.assertEqual(len(captured_queries), 1)
            qstr = captured_queries[0]['sql'].lower()
            self.assertNotIn('for update', qstr)
            forced_ordering = connection.ops.force_no_ordering()
            if forced_ordering:
                # If the backend needs to force an ordering we make sure it's
                # the only "ORDER BY" clause present in the query.
                self.assertEqual(
                    re.findall(r'order by (\w+)', qstr),
                    [', '.join(forced_ordering).lower()]
                )
            else:
                self.assertNotIn('order by', qstr)
            self.assertEqual(qstr.count(' join '), 0)

    def test_decimal_max_digits_has_no_effect(self):
        Book.objects.all().delete()
        a1 = Author.objects.first()
        p1 = Publisher.objects.first()
        thedate = timezone.now()
        for i in range(10):
            Book.objects.create(
                isbn="abcde{}".format(i), name="none", pages=10, rating=4.0,
                price=9999.98, contact=a1, publisher=p1, pubdate=thedate)

        book = Book.objects.aggregate(price_sum=Sum('price'))
        self.assertEqual(book['price_sum'], Decimal("99999.80"))


class ComplexAggregateTestCase(TestCase):
    fixtures = ["aggregation.json"]

    def test_nonaggregate_aggregation_throws(self):
        with six.assertRaisesRegex(self, TypeError, 'fail is not an aggregate expression'):
            Book.objects.aggregate(fail=F('price'))

    def test_nonfield_annotation(self):
        book = Book.objects.annotate(val=Max(Value(2, output_field=IntegerField())))[0]
        self.assertEqual(book.val, 2)
        book = Book.objects.annotate(val=Max(Value(2), output_field=IntegerField()))[0]
        self.assertEqual(book.val, 2)

    def test_missing_output_field_raises_error(self):
        with six.assertRaisesRegex(self, FieldError, 'Cannot resolve expression type, unknown output_field'):
            Book.objects.annotate(val=Max(Value(2)))[0]

    def test_annotation_expressions(self):
        authors = Author.objects.annotate(combined_ages=Sum(F('age') + F('friends__age'))).order_by('name')
        authors2 = Author.objects.annotate(combined_ages=Sum('age') + Sum('friends__age')).order_by('name')
        for qs in (authors, authors2):
            self.assertEqual(len(qs), 9)
            self.assertQuerysetEqual(
                qs, [
                    ('Adrian Holovaty', 132),
                    ('Brad Dayley', None),
                    ('Jacob Kaplan-Moss', 129),
                    ('James Bennett', 63),
                    ('Jeffrey Forcier', 128),
                    ('Paul Bissex', 120),
                    ('Peter Norvig', 103),
                    ('Stuart Russell', 103),
                    ('Wesley J. Chun', 176)
                ],
                lambda a: (a.name, a.combined_ages)
            )

    def test_aggregation_expressions(self):
        a1 = Author.objects.aggregate(av_age=Sum('age') / Count('*'))
        a2 = Author.objects.aggregate(av_age=Sum('age') / Count('age'))
        a3 = Author.objects.aggregate(av_age=Avg('age'))
        self.assertEqual(a1, {'av_age': 37})
        self.assertEqual(a2, {'av_age': 37})
        self.assertEqual(a3, {'av_age': Approximate(37.4, places=1)})

    def test_order_of_precedence(self):
        p1 = Book.objects.filter(rating=4).aggregate(avg_price=(Avg('price') + 2) * 3)
        self.assertEqual(p1, {'avg_price': Approximate(148.18, places=2)})

        p2 = Book.objects.filter(rating=4).aggregate(avg_price=Avg('price') + 2 * 3)
        self.assertEqual(p2, {'avg_price': Approximate(53.39, places=2)})

    def test_combine_different_types(self):
        with six.assertRaisesRegex(self, FieldError, 'Expression contains mixed types. You must set output_field'):
            Book.objects.annotate(sums=Sum('rating') + Sum('pages') + Sum('price')).get(pk=4)

        b1 = Book.objects.annotate(sums=Sum(F('rating') + F('pages') + F('price'),
                                   output_field=IntegerField())).get(pk=4)
        self.assertEqual(b1.sums, 383)

        b2 = Book.objects.annotate(sums=Sum(F('rating') + F('pages') + F('price'),
                                   output_field=FloatField())).get(pk=4)
        self.assertEqual(b2.sums, 383.69)

        b3 = Book.objects.annotate(sums=Sum(F('rating') + F('pages') + F('price'),
                                   output_field=DecimalField())).get(pk=4)
        self.assertEqual(b3.sums, Approximate(Decimal("383.69"), places=2))

    def test_complex_aggregations_require_kwarg(self):
        with six.assertRaisesRegex(self, TypeError, 'Complex expressions require an alias'):
            Author.objects.annotate(Sum(F('age') + F('friends__age')))
        with six.assertRaisesRegex(self, TypeError, 'Complex aggregates require an alias'):
            Author.objects.aggregate(Sum('age') / Count('age'))

    def test_aggregate_over_complex_annotation(self):
        qs = Author.objects.annotate(
            combined_ages=Sum(F('age') + F('friends__age')))

        age = qs.aggregate(max_combined_age=Max('combined_ages'))
        self.assertEqual(age['max_combined_age'], 176)

        age = qs.aggregate(max_combined_age_doubled=Max('combined_ages') * 2)
        self.assertEqual(age['max_combined_age_doubled'], 176 * 2)

        age = qs.aggregate(
            max_combined_age_doubled=Max('combined_ages') + Max('combined_ages'))
        self.assertEqual(age['max_combined_age_doubled'], 176 * 2)

        age = qs.aggregate(
            max_combined_age_doubled=Max('combined_ages') + Max('combined_ages'),
            sum_combined_age=Sum('combined_ages'))
        self.assertEqual(age['max_combined_age_doubled'], 176 * 2)
        self.assertEqual(age['sum_combined_age'], 954)

        age = qs.aggregate(
            max_combined_age_doubled=Max('combined_ages') + Max('combined_ages'),
            sum_combined_age_doubled=Sum('combined_ages') + Sum('combined_ages'))
        self.assertEqual(age['max_combined_age_doubled'], 176 * 2)
        self.assertEqual(age['sum_combined_age_doubled'], 954 * 2)

    def test_values_annotation_with_expression(self):
        # ensure the F() is promoted to the group by clause
        qs = Author.objects.values('name').annotate(another_age=Sum('age') + F('age'))
        a = qs.get(pk=1)
        self.assertEqual(a['another_age'], 68)

        qs = qs.annotate(friend_count=Count('friends'))
        a = qs.get(pk=1)
        self.assertEqual(a['friend_count'], 2)

        qs = qs.annotate(combined_age=Sum('age') + F('friends__age')).filter(pk=1).order_by('-combined_age')
        self.assertEqual(
            list(qs), [
                {
                    "name": 'Adrian Holovaty',
                    "another_age": 68,
                    "friend_count": 1,
                    "combined_age": 69
                },
                {
                    "name": 'Adrian Holovaty',
                    "another_age": 68,
                    "friend_count": 1,
                    "combined_age": 63
                }
            ]
        )

        vals = qs.values('name', 'combined_age')
        self.assertEqual(
            list(vals), [
                {
                    "name": 'Adrian Holovaty',
                    "combined_age": 69
                },
                {
                    "name": 'Adrian Holovaty',
                    "combined_age": 63
                }
            ]
        )

    def test_annotate_values_aggregate(self):
        alias_age = Author.objects.annotate(
            age_alias=F('age')
        ).values(
            'age_alias',
        ).aggregate(sum_age=Sum('age_alias'))

        age = Author.objects.values('age').aggregate(sum_age=Sum('age'))

        self.assertEqual(alias_age['sum_age'], age['sum_age'])

    def test_annotate_over_annotate(self):
        author = Author.objects.annotate(
            age_alias=F('age')
        ).annotate(
            sum_age=Sum('age_alias')
        ).get(pk=1)

        other_author = Author.objects.annotate(
            sum_age=Sum('age')
        ).get(pk=1)

        self.assertEqual(author.sum_age, other_author.sum_age)

    def test_annotated_aggregate_over_annotated_aggregate(self):
        with six.assertRaisesRegex(self, FieldError, "Cannot compute Sum\('id__max'\): 'id__max' is an aggregate"):
            Book.objects.annotate(Max('id')).annotate(Sum('id__max'))

    def test_add_implementation(self):
        try:
            # test completely changing how the output is rendered
            def lower_case_function_override(self, compiler, connection):
                sql, params = compiler.compile(self.source_expressions[0])
                substitutions = dict(function=self.function.lower(), expressions=sql)
                substitutions.update(self.extra)
                return self.template % substitutions, params
            setattr(Sum, 'as_' + connection.vendor, lower_case_function_override)

            qs = Book.objects.annotate(sums=Sum(F('rating') + F('pages') + F('price'),
                                       output_field=IntegerField()))
            self.assertEqual(str(qs.query).count('sum('), 1)
            b1 = qs.get(pk=4)
            self.assertEqual(b1.sums, 383)

            # test changing the dict and delegating
            def lower_case_function_super(self, compiler, connection):
                self.extra['function'] = self.function.lower()
                return super(Sum, self).as_sql(compiler, connection)
            setattr(Sum, 'as_' + connection.vendor, lower_case_function_super)

            qs = Book.objects.annotate(sums=Sum(F('rating') + F('pages') + F('price'),
                                       output_field=IntegerField()))
            self.assertEqual(str(qs.query).count('sum('), 1)
            b1 = qs.get(pk=4)
            self.assertEqual(b1.sums, 383)

            # test overriding all parts of the template
            def be_evil(self, compiler, connection):
                substitutions = dict(function='MAX', expressions='2')
                substitutions.update(self.extra)
                return self.template % substitutions, ()
            setattr(Sum, 'as_' + connection.vendor, be_evil)

            qs = Book.objects.annotate(sums=Sum(F('rating') + F('pages') + F('price'),
                                       output_field=IntegerField()))
            self.assertEqual(str(qs.query).count('MAX('), 1)
            b1 = qs.get(pk=4)
            self.assertEqual(b1.sums, 2)
        finally:
            delattr(Sum, 'as_' + connection.vendor)

    def test_complex_values_aggregation(self):
        max_rating = Book.objects.values('rating').aggregate(
            double_max_rating=Max('rating') + Max('rating'))
        self.assertEqual(max_rating['double_max_rating'], 5 * 2)

        max_books_per_rating = Book.objects.values('rating').annotate(
            books_per_rating=Count('id') + 5
        ).aggregate(Max('books_per_rating'))
        self.assertEqual(
            max_books_per_rating,
            {'books_per_rating__max': 3 + 5})

    def test_expression_on_aggregation(self):

        # Create a plain expression
        class Greatest(Func):
            function = 'GREATEST'

            def as_sqlite(self, compiler, connection):
                return super(Greatest, self).as_sql(compiler, connection, function='MAX')

        qs = Publisher.objects.annotate(
            price_or_median=Greatest(Avg('book__rating'), Avg('book__price'))
        ).filter(price_or_median__gte=F('num_awards')).order_by('pk')
        self.assertQuerysetEqual(
            qs, [1, 2, 3, 4], lambda v: v.pk)

        qs2 = Publisher.objects.annotate(
            rating_or_num_awards=Greatest(Avg('book__rating'), F('num_awards'),
                                          output_field=FloatField())
        ).filter(rating_or_num_awards__gt=F('num_awards')).order_by('pk')
        self.assertQuerysetEqual(
            qs2, [1, 2], lambda v: v.pk)

    def test_backwards_compatibility(self):

        class SqlNewSum(sql_aggregates.Aggregate):
            sql_function = 'SUM'

        class NewSum(Aggregate):
            name = 'Sum'

            def add_to_query(self, query, alias, col, source, is_summary):
                klass = SqlNewSum
                aggregate = klass(
                    col, source=source, is_summary=is_summary, **self.extra)
                query.annotations[alias] = aggregate

        with warnings.catch_warnings():
            warnings.simplefilter("ignore", RemovedInDjango20Warning)
            qs = Author.objects.values('name').annotate(another_age=NewSum('age') + F('age'))
            a = qs.get(pk=1)
            self.assertEqual(a['another_age'], 68)