什么是新版本 Django 中 DateModifierNode 的替代品 [英] What is the replacement for DateModifierNode in new versions of Django

问题描述

我想根据一个模型的两个字段做一个查询，一个日期，一个 int 偏移量，用作 timedelta

I want to do a query based on two fields of a model, a date, offset by an int, used as a timedelta

model.objects.filter(last_date__gte=datetime.now()-timedelta(days=F('interval')))

不可行，因为 F() 表达式不能传递到 timedelta

is a no-go, as a F() expression cannot be passed into a timedelta

稍微挖掘一下，我发现了 DateModifierNode - 虽然它似乎在这次提交中被删除了:https://github.com/django/django/commit/cbb5cdd155668ba771cad6b975676d3b20fed37b(来自这个现已过时的问题 Django:在查询中的 datetime.timedelta 中使用 F 参数)

A little digging, and I discovered DateModifierNode - though it seems it was removed in this commit: https://github.com/django/django/commit/cbb5cdd155668ba771cad6b975676d3b20fed37b (from this now-outdated SO question Django: Using F arguments in datetime.timedelta inside a query)

提交提到:

.dates() 查询是通过使用自定义 Query、QuerySet、和编译器类.而是通过使用表达式和数据库转换器 API.

The .dates() queries were implemented by using custom Query, QuerySet, and Compiler classes. Instead implement them by using expressions and database converters APIs.

这听起来很明智，而且仍然应该有一种快速简便的方法 - 但我一直在寻找如何做到这一点太久没有结果 - 有谁知道答案吗?

which sounds sensible, and like there should still be a quick easy way - but I've been fruitlessly looking for how to do that for a little too long - anyone know the answer?

推荐答案

在 Django 1.10 中，有更简单的方法可以做到这一点，但您需要稍微更改模型:使用 DurationField.我的模型如下:

In Django 1.10 there's simpler method to do it but you need to change the model a little: use a DurationField. My model is as follows:

class MyModel(models.Model):

    timeout = models.DurationField(default=86400 * 7)  # default: week
    last = models.DateTimeField(auto_now_add=True)

以及查找 last 在 now 减去 timeout 之前的对象的查询是:

and the query to find objects where last was before now minus timeout is:

MyModel.objects.filter(last__lt=datetime.datetime.now()-F('timeout'))

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