複雜的Django DB訂貨

Question

我有以下兩種模式：

class OrderItem(models.Model): 
    order = models.ForeignKey(Order, related_name='items') 
    title = models.ForeignKey(Title, related_name='order_items') 

class OrderNotes(models.Model): 
    order_item = models.ForeignKey('OrderItem', blank=True, null=True) 
    timestamp = models.DateTimeField(auto_now_add=True) 
    is_active = models.BooleanField(default=True) 

由最近OrderNote是活動我將如何排序OrderItem S'

在pseudo_code：

OrderItem.objects.order_by('ordernotes_set.order_by('is_active', '-timestamp')) 

？

Answer 1

我認爲你可以使用註釋來處理這個相當容易。 https://docs.djangoproject.com/en/dev/topics/db/aggregation/#following-relationships-backwards

from django.db.models import Max 
OrderItems.annotate(newest_note_time=Max('ordernotes__timestamp')) 
    .order_by('-ordernotes__is_active', '-newest_note_time')