django - 将Django从1.6升级到1.8 : Invalid field name(s) given in select_related

Question

我确实将项目从Django 1.6.7更新到1.8.7，并且在Django 1.8中遇到了以下异常，尽管在Django 1.6中它的代码是正确的:

In[2]: from apps.route import models
In[3]: models.Trace.objects.select_related("trace_points")
Out[3]: <repr(<django.db.models.query.QuerySet at 0x3b50c10>) failed: django.core.exceptions.FieldError: Invalid field name(s) given in select_related: 'trace_points'. Choices are: user>

我的模特:

class Trace(SocialMixin, models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='traces')
    name = models.CharField(u'Название', max_length=255)
    rating = RatingField(range=5, weight=0)
    start_date = models.DateTimeField(u'Дата старта')
    finish_date = models.DateTimeField(u'Дата окончания', null=True, blank=True)
    distance = models.DecimalField(max_digits=15, decimal_places=6, null=True, blank=True)
    created = models.DateTimeField(auto_now_add=True)
    hits = generic.GenericRelation(HitCount, object_id_field='object_pk')
    description = models.TextField(null=True, blank=True)

class TracePoint(models.Model):
    country = models.ForeignKey(Country, null=True, blank=True)
    city = models.ForeignKey(City, null=True, blank=True)
    trace = models.ForeignKey(Trace, related_name="trace_points")

我在Trace的DetailView中也遇到了这个错误，DetailView使用get_related_selections，当然我得到了“FieldError:Invalid field name ...”，为避免错误，我必须使用ManyToManyField而不是ForeigenKey？

Answer 1

Django 1.8 checks that the fields given in select_related are correct。 select_related方法可用于外键和一对一字段。不能将它用于Trace与TracePoint的反向关系。

在早期版本的Django中，Trace.objects.select_related("trace_points")不会引发错误，但是select_related()调用将无效。

您可以删除select_related()调用，或将其替换为 prefetch_related ，这将起作用。

Trace.objects.prefetch_related('trace_points')