注释然后过滤然后注释 [英] annotate then filter then annotate
本文介绍了注释然后过滤然后注释的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
代码:
now = datetime.now()
year_ago = now - timedelta(days=365)
category_list = Category.objects.annotate(suma = Sum('operation__value')) \
.filter(operation__date__gte = year_ago) \
.annotate(podsuma = Sum('operation__value'))
想法:得到每个类别的总和和一年前的总和.
The idea: get sum of each category and sum of one year back.
但此代码仅导致过滤对象;suma
等于 podsuma
.
But this code result only filtered objects; suma
is equal to podsuma
.
推荐答案
一个查询集只产生一个查询,所以所有的注释都是在同一个过滤数据集上计算的.您需要进行两次查询.
A queryset only produces one query, so all annotations are calculated over the same filtered data set. You'll need to do two queries.
更新:
做这样的事情:
在models.py中
In models.py
class Category(models.Model):
...
def suma(self):
return ...
def podsuma(self):
return ...
然后删除注释,您的 for 循环应该可以正常工作.这将意味着更多的查询,但它们会更简单,而且您可以随时缓存它们.
Then remove the annotations and your for loop should work as is. It'll mean a lot more queries, but they'll be simpler, and you can always cache them.
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