过滤最接近给定日期时间的日期时间

Question

我有一个具有日期时间字段的模型.现在给定一个特定的日期时间 - DT,我需要得到日期时间最接近DT的对象.这可能吗？

谢谢,

Answer 1

您可以通过两个查询和一些逻辑来获取它:

我们的想法是在目标日期时间之后立即找到一个对象,然后返回其中一个:

# 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

要使用一个查询来获取它,您必须将ORM退出到原始SQL.

Answer 2

只需将帕夫勒的答案更改为：

def get_closest_to_dt(qs, dt):
    greater = qs.filter(dt__gte=dt).order_by("dt").first()
    less = qs.filter(dt__lte=dt).order_by("-dt").first()

    if greater and less:
        return greater if abs(greater.dt - dt) < abs(less.dt - dt) else less
    else:
        return greater or less