如何查询一天中某个小时之前在Django中创建的对象? [英] How do I query for objects created before a certain hour in a day in Django?

问题描述

在Django中，我试图仅将查询过滤到一天中某个小时之前创建的对象.我有一个名为"created_at"的日期时间字段，用于存储创建该对象的日期时间.

In Django, I am trying to filter my query only to objects that were created before a certain hour in the day. I have a datetime field called 'created_at' that stored the datetime from which that object was created.

我想做的是:

query = query.filter(created_at__hour__lte=10)

我希望获得上午10点之前创建的所有对象.但是，当我尝试该操作时，我得到一个:

Which I would expect to get all the objects that were created before 10am. However, when I try that I get a:

FieldError: Join on field 'created_at' not permitted. Did you misspell 'hour' for the lookup type?

我可以遍历每一天并获取当天的对象，但这似乎效率很低.有没有办法可以在单个查询中做到这一点?如果没有，那么运行这种过滤器的最快方法是什么?

I could loop through each day and get that day's objects, but that seems highly inefficient. Is there a way I can do this in a single query? If not, what is the fastest way to run this sort of filter?

推荐答案

__ hour 是查找类型，因此您不能将其与其他查找混合使用像 __ lte 这样的类型.您可以使用 Q 对象(例如EG)构造一个过滤器:

__hour on a DateTimeField is a lookup type, so you can't mix it with another lookup type like __lte. You could construct a filter with Q objects, EG:

before_ten = Q(created_at__hour=0)
for hour in range(1, 11):
    before_ten = before_ten | Q(created_at__hour=hour)
query = query.filter(before_ten)

如果可以更改数据模型，则保存创建时间 TimeField 以及现有的 created_at 可能更方便.

If you can change your data model, it might be more convenient to save a creation time TimeField as well as your existing created_at.

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