过滤最接近给定日期时间的datetime [英] Filter on datetime closest to the given datetime

问题描述

我有一个具有datetime字段的模型。现在给定一个特定的datetime-DT，我需要得到datetime最接近DT的对象。这是可能吗？

谢谢，

解决方案

你可以得到它有两个查询和一些逻辑：

这个想法是找到一个紧跟在目标日期之后的对象，并返回其中一个：

 ＃这个方法是在模型的经理
 def get_closest_to（self，target）
 nearest_greater_qs = self.filter（dt__gt =目标）.order_by（'dt'）
 nearest_less_qs = self.filter（dt__lt = target）.order_by（' -  dt'）
 
 try：
 try：
 nearest_greater = nearest_greater_qs [0] 
除了IndexError：
 return nearest_less_qs [0] 
 
 try：
 nearest_less = nearest_less_qs [0] 
除了IndexError： 
 return nearest_greater_qs [0] 
除了IndexError：
 raise self.model.DoesNotExist（没有最近的对象
 因为没有对象）
 
如果nearest_greater.dt  -  target> target  -  nearest_less.dt：
 return nearest_less 
 else：
 return nearest_greater 
  

要获得一个查询，您必须将ORM退出到原始SQL。

I have a model which has a datetime field. Now given a particular datetime - DT, I need to get the object which has the datetime closest to DT. Is this possible?

Thanks,

解决方案

You can get it with two queries and some logic:

The idea is to find one object immediately following and one immediately preceding the target datetime and to return one of them:

# this method is on the model's manager
def get_closest_to(self, target)
    closest_greater_qs = self.filter(dt__gt=target).order_by('dt')
    closest_less_qs    = self.filter(dt__lt=target).order_by('-dt')

    try:
        try:
            closest_greater = closest_greater_qs[0]
        except IndexError:
            return closest_less_qs[0]

        try:
            closest_less = closest_less_qs[0]
        except IndexError:
            return closest_greater_qs[0]
    except IndexError:
        raise self.model.DoesNotExist("There is no closest object"
                                      " because there are no objects.")

    if closest_greater.dt - target > target - closest_less.dt:
        return closest_less
    else:
        return closest_greater

To get it with one query, you have to drop out of ORM to raw SQL.

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