相关模型的GeoDjango Distance()批注 [英] GeoDjango Distance() Annotation on Related Model
问题描述
我有一个 Profile
类,它是一个具有 Location
模型的OneToOne.每个配置文件都有一个唯一的位置.
I have a Profile
class which is a OneToOne with Location
model. Every profile has one and only location.
class Location(models.Model):
profile = models.OneToOne(Profile)
point = PointField()
在我的一个视图中,我显示了一个配置文件列表.例如,我首先找到具有位置的配置文件,然后找到关联的配置文件.
In one of my views, I display a list of profiles. For example, I first find profiles with locations and then find associated profiles.
ref_location = Point(0,0) # point to calculate distances from
locations = Location.objects.filter(point__distance_lte=(ref_location, D(m=50 * 1000))) \
profiles = Profile.objects.filter(pk__in=locations.values('profile_id'))
我想要的是能够知道到每个配置文件实例的距离,例如我想做类似的事情:
What I would want is to be able to know the distance to each of these profile instances, e.g. I want to do something like:
profiles = Profile.objects.filter(pk__in=locations.values('profile_id'))\
.annotate(distance=Distance('location__point', ref_location))
然后遍历
for p in profiles:
print(p.distance.km)
不可能
我可以做的是 annotate
locations
,这没什么用,因为我在模板中遍历了 profiles
,不是位置
What I can do is annotate
the locations
instead, which isn't much use, because in the template I loop over profiles
, not locations
推荐答案
您可以使用子查询(对于Django版本> = 1.11)组成此查询:
You can use Subquery (for Django version >= 1.11) to compose this query:
locations = Location.objects.filter(
point__distance_lte=(OuterRef('ref_location'), D(m=50 * 1000))
).annotate(distance=Distance(OuterRef('point'), ref_location))
profiles = Profile.objects.filter(
pk__in=Subquery(locations.values('profile_id')
).annotate(distance=Subquery(locations.values('distance')))
或者对于Django版本<1.11您可以按以下方式编写此查询:
Or for Django version < 1.11 you can compose this query as follows:
locations = Location.objects.filter(
point__distance_lte=(ref_location), D(m=50 * 1000))
).annotate(distance=Distance('point', ref_location))
profiles = Profile.objects.filter(
pk__in=locations.values('profile_id')
).annotate(distance=locations.values('distance'))
关键是要注释与 Location
对象的距离,然后注释与适当的轮廓的距离.
The point is that you annotate the distance to the Location
objects and then you annotate that distance to the appropriate profile.
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