标签: generic-relationship

说我有以下型号:

class Image(models.Model):
    image   = models.ImageField(max_length=200, upload_to=file_home)
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey()

class Article(models.Model):
    text = models.TextField()
    images = generic.GenericRelation(Image)

class BlogPost(models.Model):
    text = models.TextField()
    images = generic.GenericRelation(Image)

找到所有至少附有一个Image的文章的处理器和内存最有效的方法是什么？

我这样做了:

Article.objects.filter(pk__in=Image.objects.filter(content_type=ContentType.objects.get_for_model(Article)).values_list('object_id', flat=True))

哪个有效,但除了丑陋之外需要永远.

我怀疑使用原始SQL有一个更好的解决方案,但这超出了我的范围.对于它的价值,上面生成的SQL如下:

 SELECT `issues_article`.`id`, `issues_article`.`text` FROM `issues_article` WHERE `issues_article`.`id` IN (SELECT U0.`object_id` FROM `uploads_image` U0 WHERE U0.`content_type_id` = 26 ) LIMIT 21

编辑: czarchaic的建议有更好的语法,但更糟(更慢)的性能.他的查询生成的SQL如下所示:

SELECT DISTINCT `issues_article`.`id`, `issues_article`.`text`, COUNT(`uploads_image`.`id`) AS `num_images` FROM `issues_article` LEFT OUTER JOIN `uploads_image` ON (`issues_article`.`id` = `uploads_image`.`object_id`) GROUP BY `issues_article`.`id` …

我正在使用object_list通用视图来快速列出一组文章.每篇文章都附有评论.该查询使用注释Count()数量的注释,然后order_by()使用注释的数字.

'queryset': Article.objects.annotate(comment_count=Count('comments')).order_by('-comment_count'),

注释是django.contrib.comments框架的一部分,并通过通用关系附加到模型.我在我的文章模型中添加了显式反向查找:

class Article(models.Models):
   ...
   comments = generic.GenericRelation(Comment, content_type_field='content_type', object_id_field='object_pk')

问题是,这会计入"不活跃"的评论; 那些有is_public=False或is_removed=True.如何排除任何不活动的评论？

我运行代码来创建这个演示中的一般相关对象:http: //www.djangoproject.com/documentation/models/generic_relations/

一切都很好:

>>> bacon.tags.create(tag="fatty")
<TaggedItem: fatty>
>>> tag, newtag = bacon.tags.get_or_create(tag="fatty")
>>> tag
<TaggedItem: fatty>
>>> newtag
False

但后来我对我的应用感兴趣的用例:

>>> tag, newtag = bacon.tags.get_or_create(tag="wholesome")
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 123, in get_or_create
    return self.get_query_set().get_or_create(**kwargs)
  File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 343, in get_or_create
    raise e
IntegrityError: app_taggeditem.content_type_id may not be NULL

在查看其他代码后,我尝试了一堆随机的东西:

>>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem)
ValueError: Cannot assign "<class 'generics.app.models.TaggedItem'>": "TaggedItem.content_type" must be a "ContentType" instance.

要么:

>>> …

class Foo(models.Model):
    bar = models.CharField(max_length=300)
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')


class FooSerializer(serializers.ModelSerializer):
    class Meta:
       model = Foo

class FooViewSet(viewsets.ModelViewSet):
    model = Foo
    serializer_class = FooSerializer

我现在可以将数据发布到如下所示的视图集:

{
    bar: 'content',
    content_type: 1
    object_id: 5
}

唯一让我烦恼的是,前端必须要注意contenttype id

相反,我希望能够将content_types名称发布为'User'作为content_type,并让后端确定id.

我想遍历我的Django模板中的泛型关系,类似于如何遍历FK关系.

Models.py

class Company(models.Model):
    name = models.CharField(blank=True, max_length=100)
    notes = models.TextField(blank=True)

class Address(models.Model):
    address = models.TextField(max_length=200)
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey('content_type', 'object_id')

这在我的模板中似乎不起作用:

{{ company.address_set.all }}

任何帮助表示赞赏.