Fungsi pengumpulan khusus PostgreSQL

Fungsi-fungsi ini tersedia dari modul``django.contrib.postgres.aggregates``. Mereka digambarkan dalam lebih rinci dalam PostgreSQL docs.

Catatan

All functions come without default aliases, so you must explicitly provide one. For example:

>>> SomeModel.objects.aggregate(arr=ArrayAgg("somefield"))
{'arr': [0, 1, 2]}

Pilihan pengumpulan umum

All aggregates have the filter keyword argument and most also have the default keyword argument.

Fungsi pengumpulan tujuan-umum

ArrayAgg

class ArrayAgg(expression, distinct=False, filter=None, default=None, ordering=(), **extra)

Returns a list of values, including nulls, concatenated into an array, or default if there are no values.

distinct

Sebuah argumen boolean pilihan yang menentukan jika nilai senarai akan berbeda. Awalan pada False.

ordering

Sebuah string pilihan dari sebuah nama bidang (dengan sebuah awalan "-" pilihan yang menunjukkan urutan menurun) atau sebuah pernyataan (atau sebuah tuple atau list dari string dan/atau pernyataan) yang menentukan urutan dari unsur dalam daftar hasil.

Contoh:

"some_field"
"-some_field"
from django.db.models import F

F("some_field").desc()

Ditinggalkan sejak versi 4.0: If there are no rows and default is not provided, ArrayAgg returns an empty list instead of None. This behavior is deprecated and will be removed in Django 5.0. If you need it, explicitly set default to Value([]).

BitAnd

class BitAnd(expression, filter=None, default=None, **extra)

Returns an int of the bitwise AND of all non-null input values, or default if all values are null.

BitOr

class BitOr(expression, filter=None, default=None, **extra)

Returns an int of the bitwise OR of all non-null input values, or default if all values are null.

BitXor

New in Django 4.1.
class BitXor(expression, filter=None, default=None, **extra)

Returns an int of the bitwise XOR of all non-null input values, or default if all values are null. It requires PostgreSQL 14+.

BoolAnd

class BoolAnd(expression, filter=None, default=None, **extra)

Returns True, if all input values are true, default if all values are null or if there are no values, otherwise False.

Contoh penggunaan:

class Comment(models.Model):
    body = models.TextField()
    published = models.BooleanField()
    rank = models.IntegerField()
>>> from django.db.models import Q
>>> from django.contrib.postgres.aggregates import BoolAnd
>>> Comment.objects.aggregate(booland=BoolAnd("published"))
{'booland': False}
>>> Comment.objects.aggregate(booland=BoolAnd(Q(rank__lt=100)))
{'booland': True}

BoolOr

class BoolOr(expression, filter=None, default=None, **extra)

Returns True if at least one input value is true, default if all values are null or if there are no values, otherwise False.

Contoh penggunaan:

class Comment(models.Model):
    body = models.TextField()
    published = models.BooleanField()
    rank = models.IntegerField()
>>> from django.db.models import Q
>>> from django.contrib.postgres.aggregates import BoolOr
>>> Comment.objects.aggregate(boolor=BoolOr("published"))
{'boolor': True}
>>> Comment.objects.aggregate(boolor=BoolOr(Q(rank__gt=2)))
{'boolor': False}

JSONBAgg

class JSONBAgg(expressions, distinct=False, filter=None, default=None, ordering=(), **extra)

Returns the input values as a JSON array, or default if there are no values. You can query the result using key and index lookups.

distinct

Sebuah argumen boolean pilihan yang menentukan jika nilai senarai akan berbeda. Awalan pada False.

ordering

Sebuah string pilihan dari sebuah nama bidang (dengan sebuah awalan "-" pilihan yang menunjukkan urutan menurun) atau sebuah pernyataan (atau sebuah tuple atau list dari string dan/atau pernyataan) yang menentukan urutan dari unsur dalam daftar hasil.

Contoh-contoh adalah sama seperti untuk ArrayAgg.ordering.

Contoh penggunaan:

class Room(models.Model):
    number = models.IntegerField(unique=True)


class HotelReservation(models.Model):
    room = models.ForeignKey("Room", on_delete=models.CASCADE)
    start = models.DateTimeField()
    end = models.DateTimeField()
    requirements = models.JSONField(blank=True, null=True)
>>> from django.contrib.postgres.aggregates import JSONBAgg
>>> Room.objects.annotate(
...     requirements=JSONBAgg(
...         "hotelreservation__requirements",
...         ordering="-hotelreservation__start",
...     )
... ).filter(requirements__0__sea_view=True).values("number", "requirements")
<QuerySet [{'number': 102, 'requirements': [
    {'parking': False, 'sea_view': True, 'double_bed': False},
    {'parking': True, 'double_bed': True}
]}]>

Ditinggalkan sejak versi 4.0: If there are no rows and default is not provided, JSONBAgg returns an empty list instead of None. This behavior is deprecated and will be removed in Django 5.0. If you need it, explicitly set default to Value('[]').

StringAgg

class StringAgg(expression, delimiter, distinct=False, filter=None, default=None, ordering=())

Returns the input values concatenated into a string, separated by the delimiter string, or default if there are no values.

delimiter

Diwajibkan argumen. Butuh berupa sebuah string.

distinct

Sebuah argumen boolean pilihan yang menentukan jika nilai yang digabungkan akan berbeda. Awalan menjadi False.

ordering

Sebuah string pilihan dari sebuah bidang nama (dengan awalan "-" pilihan yang menunjukkan urutan menurun) atau sebuah pernyataan (atau sebuah tuple atau list dari string dan/atau pernyataan) yang menentukan urutan dari unsur dalam hasil string.

Contoh-contoh adalah sama seperti untuk ArrayAgg.ordering.

Contoh penggunaan:

class Publication(models.Model):
    title = models.CharField(max_length=30)


class Article(models.Model):
    headline = models.CharField(max_length=100)
    publications = models.ManyToManyField(Publication)
>>> article = Article.objects.create(headline="NASA uses Python")
>>> article.publications.create(title="The Python Journal")
<Publication: Publication object (1)>
>>> article.publications.create(title="Science News")
<Publication: Publication object (2)>
>>> from django.contrib.postgres.aggregates import StringAgg
>>> Article.objects.annotate(
...     publication_names=StringAgg(
...         "publications__title",
...         delimiter=", ",
...         ordering="publications__title",
...     )
... ).values("headline", "publication_names")
<QuerySet [{
    'headline': 'NASA uses Python', 'publication_names': 'Science News, The Python Journal'
}]>

Ditinggalkan sejak versi 4.0: If there are no rows and default is not provided, StringAgg returns an empty string instead of None. This behavior is deprecated and will be removed in Django 5.0. If you need it, explicitly set default to Value('').

Fungsi-fungsi pengumpulan untuk statistik

y dan x

Argumen-argumen y dan x untuk semua fungsi-fungsi ini dapat dinamai dari bidang atau sebuah pernyataan mengembalikan data numerik. Kedua diwajibkan.

Corr

class Corr(y, x, filter=None, default=None)

Returns the correlation coefficient as a float, or default if there aren't any matching rows.

CovarPop

class CovarPop(y, x, sample=False, filter=None, default=None)

Returns the population covariance as a float, or default if there aren't any matching rows.

sample

Optional. By default CovarPop returns the general population covariance. However, if sample=True, the return value will be the sample population covariance.

RegrAvgX

class RegrAvgX(y, x, filter=None, default=None)

Returns the average of the independent variable (sum(x)/N) as a float, or default if there aren't any matching rows.

RegrAvgY

class RegrAvgY(y, x, filter=None, default=None)

Returns the average of the dependent variable (sum(y)/N) as a float, or default if there aren't any matching rows.

RegrCount

class RegrCount(y, x, filter=None)

Mengembalikan sebuah int dari angka dari baris masukan dimana kedua pernyataan tidak null.

Catatan

The default argument is not supported.

RegrIntercept

class RegrIntercept(y, x, filter=None, default=None)

Returns the y-intercept of the least-squares-fit linear equation determined by the (x, y) pairs as a float, or default if there aren't any matching rows.

RegrR2

class RegrR2(y, x, filter=None, default=None)

Returns the square of the correlation coefficient as a float, or default if there aren't any matching rows.

RegrSlope

class RegrSlope(y, x, filter=None, default=None)

Returns the slope of the least-squares-fit linear equation determined by the (x, y) pairs as a float, or default if there aren't any matching rows.

RegrSXX

class RegrSXX(y, x, filter=None, default=None)

Returns sum(x^2) - sum(x)^2/N ("sum of squares" of the independent variable) as a float, or default if there aren't any matching rows.

RegrSXY

class RegrSXY(y, x, filter=None, default=None)

Returns sum(x*y) - sum(x) * sum(y)/N ("sum of products" of independent times dependent variable) as a float, or default if there aren't any matching rows.

RegrSYY

class RegrSYY(y, x, filter=None, default=None)

Returns sum(y^2) - sum(y)^2/N ("sum of squares" of the dependent variable) as a float, or default if there aren't any matching rows.

Contoh penggunaan

We will use this example table:

| FIELD1 | FIELD2 | FIELD3 |
|--------|--------|--------|
|    foo |      1 |     13 |
|    bar |      2 | (null) |
|   test |      3 |     13 |

Here's some examples of some of the general-purpose aggregation functions:

>>> TestModel.objects.aggregate(result=StringAgg("field1", delimiter=";"))
{'result': 'foo;bar;test'}
>>> TestModel.objects.aggregate(result=ArrayAgg("field2"))
{'result': [1, 2, 3]}
>>> TestModel.objects.aggregate(result=ArrayAgg("field1"))
{'result': ['foo', 'bar', 'test']}

The next example shows the usage of statistical aggregate functions. The underlying math will be not described (you can read about this, for example, at wikipedia):

>>> TestModel.objects.aggregate(count=RegrCount(y="field3", x="field2"))
{'count': 2}
>>> TestModel.objects.aggregate(
...     avgx=RegrAvgX(y="field3", x="field2"), avgy=RegrAvgY(y="field3", x="field2")
... )
{'avgx': 2, 'avgy': 13}