GeoDjango对于外键关系的距离查询 [英] GeoDjango distance query for a ForeignKey Relationship

问题描述

我有以下模型（简化）

from django.contrib.gis.db import models as geomodels

modelB (geomodels.Model):
    objects = geomodels.GeoManager()

modelA (geomodels.Model):
    point   =   geomodels.PointField(unique=True)
    mb      =   models.ForeignKey(modelB,related_name='modela')
    objects =   geomodels.GeoManager()

我试图找到所有的modelB对象，并将它们与给定位置的距离进行排序（其中距离定义为给定位置与关联的modelA的点对象之间的距离）。当我尝试运行查询

I am trying to find all modelB objects and sort them by distance from a given location (where distance is defined as distance between a given location and the point object of associated modelA). When I try to run the query

modelB.objects.distance((loc, field_name='modela__point')

我收到错误说

TypeError: ST_Distance output only available on GeometryFields. 

请注意，loc是一个Point对象。但是，当我运行查询

Note that loc is a Point object.However, when I run the query

modelB.objects.filter(modela__point__distance_lte = (loc, 1000)) 

此查询工作没有错误和预期。

this query works without error and as expected.

任何想法这个错误可能是什么？我使用的是django 1.2.4 PostGis 1.5.2 PostGres 8.4。

Any idea what the mistake could be? I am using django 1.2.4, PostGis 1.5.2, PostGres 8.4.

谢谢。

推荐答案

对于第一个，您需要将其更改为：

For the first one, you will need to change it to:

modelB.objects.all().distance(loc, field_name='modela__point')

如果你想要查看所有的modelB对象。

if you want to see all modelB objects.

.distance用于计算和向QuerySet（或GeoQuerySet）的每个结果行添加一个距离字段。

The ".distance" is used to calculate and add a distance field to each resulting row of the QuerySet (or GeoQuerySet).

这篇关于GeoDjango对于外键关系的距离查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！