django

저는 항상 Django에서 여러 filter () 호출을 연결하는 것이 단일 호출로 수집하는 것과 항상 동일하다고 가정했습니다.

# Equivalent
Model.objects.filter(foo=1).filter(bar=2)
Model.objects.filter(foo=1,bar=2)

하지만 나는 이것이 사실이 아닌 내 코드에서 복잡한 쿼리 세트를 실행했습니다.

class Inventory(models.Model):
    book = models.ForeignKey(Book)

class Profile(models.Model):
    user = models.OneToOneField(auth.models.User)
    vacation = models.BooleanField()
    country = models.CharField(max_length=30)

# Not Equivalent!
Book.objects.filter(inventory__user__profile__vacation=False).filter(inventory__user__profile__country='BR')
Book.objects.filter(inventory__user__profile__vacation=False, inventory__user__profile__country='BR')

생성 된 SQL은

SELECT "library_book"."id", "library_book"."asin", "library_book"."added", "library_book"."updated" FROM "library_book" INNER JOIN "library_inventory" ON ("library_book"."id" = "library_inventory"."book_id") INNER JOIN "auth_user" ON ("library_inventory"."user_id" = "auth_user"."id") INNER JOIN "library_profile" ON ("auth_user"."id" = "library_profile"."user_id") INNER JOIN "library_inventory" T5 ON ("library_book"."id" = T5."book_id") INNER JOIN "auth_user" T6 ON (T5."user_id" = T6."id") INNER JOIN "library_profile" T7 ON (T6."id" = T7."user_id") WHERE ("library_profile"."vacation" = False  AND T7."country" = BR )
SELECT "library_book"."id", "library_book"."asin", "library_book"."added", "library_book"."updated" FROM "library_book" INNER JOIN "library_inventory" ON ("library_book"."id" = "library_inventory"."book_id") INNER JOIN "auth_user" ON ("library_inventory"."user_id" = "auth_user"."id") INNER JOIN "library_profile" ON ("auth_user"."id" = "library_profile"."user_id") WHERE ("library_profile"."vacation" = False  AND "library_profile"."country" = BR )

연결 filter()호출 이있는 첫 번째 쿼리 세트 는 인벤토리 모델에 두 번 효과적으로 결합하여 두 조건 사이에 OR을 생성하는 반면 두 번째 쿼리 세트는 두 조건을 함께 AND로 만듭니다. 첫 번째 쿼리와 두 가지 조건이있을 것으로 예상했습니다. 이것이 예상되는 동작입니까 아니면 Django의 버그입니까?

관련 질문에 대한 답변 Django에서 “.filter (). filter (). filter () …”사용에 대한 단점이 있습니까? 두 쿼리 세트가 동일해야 함을 나타냅니다.

답변

from django.db import models

class Blog(models.Model):
    ...

class Entry(models.Model):
    blog = models.ForeignKey(Blog)
    headline = models.CharField(max_length=255)
    pub_date = models.DateField()
    ...

Blog.objects.filter(entry__headline_contains='Lennon',
    entry__pub_date__year=2008)
Blog.objects.filter(entry__headline_contains='Lennon').filter(
    entry__pub_date__year=2008)  

Blog.objects.filter(entry__headline__contains='Lennon', entry__pub_date__year=2008)

Blog.objects.filter(entry__headline__contains='Lennon').filter(entry__pub_date__year=2008)

Book.objects.filter(inventory__user__profile__vacation=False, inventory__user__profile__country='BR')

def your_dynamic_query_generator(self, event: Event):
    qs \
    .filter(shiftregistrations__event=event) \
    .filter(shiftregistrations__shifts=False)

def your_dynamic_query_generator(self, event: Event):
    return Q(shiftregistrations__event=event) & Q(shiftregistrations__shifts=False)

qs: EventQuerySet = qs.annotate(
    num_shifts=Count('shiftregistrations__shifts', filter=Q(shiftregistrations__event=event))
)

def your_dynamic_query_generator(self):
    return Q(num_shifts=0)