Django在注释中将timedelta转换为整数 [英] Django convert timedelta to integer in annotation

问题描述

我要注释两个日期之间的差异，然后汇总四舍五入的平均值.问题在于两个日期之间的差异是 datetime.timedelta ，所以我得到了错误:

I'm annotating the difference between two dates then aggregating the rounded average. The problem is that the difference between the two dates is a datetime.timedelta so I am getting the error:

django.db.utils.ProgrammingError:无法将类型间隔强制转换为数字

django.db.utils.ProgrammingError: cannot cast type interval to numeric

如何在 Avg()中使用整数 days_to_pay.days ?

def aggregate_ar_detail(self):
    queryset = self.annotate(
        days_to_pay=Case(
            When(Q(date_paid__isnull=False), then=F('date_paid') - F('date_trans')),
            default=None,
        )
    ).aggregate(
        avg_days=Round(Avg('days_to_pay')),
    )

我尝试在 models.IntegerField()的注解中指定输出字段，但这会导致:

I've tried specifying the output field on the annotation a models.IntegerField() but it causes:

TypeError:float()参数必须是字符串或数字，而不是'datetime.timedelta'

TypeError: float() argument must be a string or a number, not 'datetime.timedelta'

推荐答案

设法使其与

Managed to get it working with ExtractDay

from django.db.models.functions import ExtractDay

def aggregate_ar_detail(self):
    queryset = self.annotate(
        days_to_pay=Case(
            When(Q(date_paid__isnull=False), then=F('date_paid') - F('date_trans')),
            default=None,
        )
    ).aggregate(
        avg_days=Round(Avg(ExtractDay('days_to_pay'))),
    )

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