我正在尝试使用 Django 的反向通用关系通过 Django 的 ORM 访问和过滤相关对象。请参见下面声明的模型:
from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
from django.contrib.contenttypes.models import ContentType
from django.db import models
class Status(models.Model):
name = models.CharField(max_length=100)
def __str__(self):
return self.name
class Package(models.Model):
name = models.CharField(max_length=500)
status = models.ForeignKey(Status, on_delete=models.PROTECT)
hst_entries = GenericRelation("myapp.StatusHistory", related_query_name="package")
def __str__(self):
return self.name
class StatusHistory(models.Model):
content_type = models.ForeignKey(ContentType, on_delete=models.PROTECT)
object_id = models.TextField()
object = GenericForeignKey("content_type", "object_id")
status = models.ForeignKey(Status, on_delete=models.PROTECT)
entry_added = models.DateTimeField(auto_now_add=True)
def __str__(self):
return f"{self.content_type} - {self.object_id}: {self.status.name}"
Package
如您所见,StatusHistory
模型之间存在通用关系。StatusHistory
为了从我尝试的模型访问相关包:
StatusHistory.objects.filter(package__name__startswith="pack")
结果:
ProgrammingError: operator does not exist: text = integer
LINE 1: ...kage" ON ("myapp_statushistory"."object_id" = "myapp...
^
HINT: No operator matches the given name and argument types. You might need to add explicit type casts.
我了解 PostgreSQL 抱怨object_id
(StatusHistory
模型)和id
(Package
模型)字段之间的类型不匹配。这种不匹配可以通过 PostgreSQL cast operator 解决,::
如下所示:
### WRONG
join myapp_package on (myapp_statushistory.object_id = my_app_package.id)
### RIGHT
join myapp_package on (myapp_statushistory.object_id = my_app_package.id::varchar)
有没有可能通过 Django 的 ORM 进行这种转换?
注意:将object_id
字段转换IntegerField
为不是我的选择。