Как получить присоединенный последний объект в Django ORM? ⇐ Python

[Anonymous]

У меня есть две таблицы, связанные 1:N.
Я хочу получить только одну последнюю модель сделки для каждой модели Real_estate.

Код: Выделить всё

class RealEstate(gis_models.Model):
class Meta:
db_table = "real_estate"

id = models.BigAutoField(primary_key=True, auto_created=True)
name = models.CharField(
help_text="부동산 이름", null=True, blank=True, max_length=30
)
build_year = models.SmallIntegerField(
help_text="건축년도", null=False, blank=False
)
regional_code = models.CharField(
help_text="지역코드",
null=False,
blank=False,
max_length=6,
)
lot_number = models.CharField(
help_text="지번(구획마다 부여된 땅 번호, 서울특별시 서초구 반포동 1-1)",
null=False,
blank=False,
max_length=50,
)
road_name_address = models.CharField(
help_text="도로명 주소", null=True, blank=True, max_length=50
)
address = models.CharField(
help_text="주소", null=True, blank=True, max_length=50
)
real_estate_type = models.CharField(
help_text="부동산 타입",
choices=REAL_ESTATE_TYPES,
max_length=20,
)
latitude = models.CharField(
help_text="위도", null=False, blank=False, max_length=20
)
longitude = models.CharField(
help_text="경도", null=False, blank=False, max_length=20
)
point = gis_models.PointField(geography=True, null=False, blank=False)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)

class Deal(models.Model):
class Meta:
db_table = "deal"

id = models.BigAutoField(primary_key=True, auto_created=True)

deal_price = models.PositiveIntegerField(
help_text="거래금액(전월세 보증금)", null=False, blank=False
)
brokerage_type = models.CharField(
help_text="중개/직거래(거래유형)",
null=True,
blank=True,
choices=BROKERAGE_TYPES,
max_length=10,
)
deal_year = models.SmallIntegerField(
help_text="계약년도(년)", null=False, blank=False
)
land_area = models.CharField(
help_text="대지권면적", null=False, blank=False, max_length=10
)
deal_month = models.SmallIntegerField(
help_text="계약 월", null=False, blank=False
)
deal_day = models.SmallIntegerField(
help_text="계약 일", null=False, blank=False
)
area_for_exclusive_use = models.CharField(
help_text="전용면적(제곱미터)", null=False, blank=False, max_length=10
)
floor = models.CharField(
help_text="층", null=False, blank=False, max_length=3
)
is_deal_canceled = models.BooleanField(
help_text="해제여부(거래계약이 무효, 취소, 해제)",
null=False,
blank=False,
)
deal_canceled_date = models.DateField(
help_text="해제사유 발생일", null=True, blank=True
)
area_for_exclusive_use_pyung = models.CharField(
help_text="전용면적(평)", null=False, blank=False, max_length=7
)
area_for_exclusive_use_price_per_pyung = models.CharField(
help_text="전용면적 평당가", null=False, blank=False, max_length=8
)
deal_type = models.CharField(
help_text="유형(DEAL(매매), JEONSE(전세), MONTHLY_RENT(월세))",
null=False,
blank=False,
choices=DEAL_TYPES,
max_length=13,
)
created_at = models.DateTimeField(auto_now_add=True)
updated_at = models.DateTimeField(auto_now=True)

real_estate = models.ForeignKey(
"RealEstate",
related_name="deals",
on_delete=models.DO_NOTHING,
)

Я присоединился с помощью prefetch_related, и результатом list(real_estates)[0].latest_deals является [].

Код: Выделить всё

            latest_deals = (
deal_q.filter(real_estate_id=OuterRef("id"))
.order_by("-deal_year", "-deal_month",  "-deal_day")
.values("id")[:1]
)

real_estates = (
RealEstate.objects.prefetch_related(
Prefetch(
lookup="deals",
queryset=deal_q.filter(id__in=Subquery(latest_deals)),
to_attr="latest_deals",
)
)
.filter(
deals__is_deal_canceled=False,
latitude__gte=dto.sw_lat,
latitude__lte=dto.ne_lat,
longitude__gte=dto.sw_lng,
longitude__lte=dto.ne_lng,
)
.distinct()
)

list(real_estates)[0].latest_deals

В чем проблема такого подхода?

Подробнее здесь: https://stackoverflow.com/questions/786 ... django-orm