django

Question

我有一个用户活动模型：

class Activity(models.Model):
    actor = models.ForeignKey(User)
    action = models.CharField(max_length=100)
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey('content_type', 'object_id')
    pub_date = models.DateTimeField(auto_now_add=True, auto_now=False)

    class Meta:
        verbose_name = 'Activity'
        verbose_name_plural = 'Activities'
        ordering = ['-pub_date']

    def __unicode__(self):
        return ("%s %s") % (self.actor.username, self.action)

观看次数：

def home(request):
    if request.user.is_authenticated():
        user = request.user
        userP = Person.objects.get_or_create(user=user)
        userP = userP[0]
        following = userP.get_following()
        users = []
        actors = list(following.values_list('user', flat=True)) + [user.id]
        activities = Activity.objects.filter(actor__in=actors)

更新

假设有 3 个用户喜欢相同的状态，而用户 3 是最后一个喜欢该状态的人。现在将创建 3 个活动，分别为 "User1 liked status"、"User2 liked status"、"User3 liked status"。我想要的是每个状态只得到一个 activity，这是最近的一个。所以在这种情况下它将是 "User3 liked status".

状态模型：

class Status(models.Model):
    body = models.TextField(max_length=200)
    image = models.ImageField(blank=True, null=True, upload_to=get_upload_file_name)
    privacy = models.CharField(max_length=1,choices=PRIVACY, default='F')
    pub_date = models.DateTimeField(auto_now_add=True, auto_now=False)
    user = models.ForeignKey(User)
    hearts = generic.GenericRelation(Heart, null=True, blank=True)

class Heart(models.Model):
    user = models.ForeignKey(User)
    pub_date = models.DateTimeField(auto_now_add=True, auto_now=False)
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey('content_type', 'object_id')

更新

这是signals.py为每个对象（心或状态）创建activity：

def create_activity_item(sender, instance, signal, *args, **kwargs):
    if kwargs.get('created', True):
        ctype = ContentType.objects.get_for_model(instance)
        if ctype.name == 'Status':
            action = ' shared '

            activity = Activity.objects.get_or_create(
                actor = instance.user,
                action = action,
                content_type = ctype,
                object_id = instance.id,
                pub_date = instance.pub_date
            )

        if ctype.name == 'Heart':
            action = ' gave heart to '

            activity = Activity.objects.get_or_create(
                actor = instance.user,
                action = action,
                content_type = ctype,
                object_id = instance.id,
                pub_date = instance.pub_date
            )

for modelname in [Status, Heart]:
    post_save.connect(create_activity_item, sender=modelname,
                  dispatch_uid="create_activity_item")

Answer 1

activities = Activity.objects.filter(actor__in=users).distinct('content_type', 'object_id', 'action')

如果您的数据库不支持 DISTINCT ON 查询，您可以进行查询，然后通过对象手动运行查找不同的值：

unique_activities = []
activities = Activity.objects.filter(actor__in=users)
for activity in activities:
    unseen = True
    for unique_activity in unique_activities:
        if (activity.action == unique_activity.action and activity.content_type == unique_activity.content_type and activity.object_id == unique_activity.object_id):
            unseen = False
            break
    if unseen:
         unique_activities.append(activity)

print unique_activities

Answer 2

这听起来像是一个 greatest-per-group 问题。你能试试这个吗:

activities = Activity.objects.filter(
    id__in=Activity.objects.values('content_type') \
        .annotate(max_id=Max('id')) \
        .values_list('max_id', flat=True) \
)

Answer 3

这仅适用于 PostgreSQL：

Activity.objects.order_by('action', 'content_type_id', 'object_id', '-pub_date').distinct('action', 'content_type_id', 'object_id').filter(actor__in=actors)

django - 按模型的不同字段过滤 class

django - Filter by distinct fields of a model class

django-views