Question

我有两个模型如下：

from django.db import models

class Category(models.Model):
    name = models.CharField(max_length=20, verbose_name="Name")

    def __str__(self):
        return self.name


class Event(models.Model):
    category = models.ForeignKey(Category, related_name="events", on_delete=models.CASCADE, verbose_name="Category")
    started_at = models.DateTimeField(verbose_name="Started at")
    ended_at = models.DateTimeField(null=True, blank=True, verbose_name="Ended at")
    name = models.CharField(max_length=20, verbose_name="Name")

    def __str__(self):
        return self.name

我试图获得一个类别的特定时间段（如上个月）的总事件持续时间。

我可以得到总数（没有指定时间段）这样的持续时间：

from datetime import timedelta

from django.db import models
from django.db.modals.functions import Coalesce
from django.utils.timezone import now

Category.objects \
    .filter(id=1) \
    .annotate(
        events_duration=Coalesce(
            models.Sum(
                Coalesce(models.F('events__ended_at'), now()) - models.F('events__started_at'),
            ),
            models.Value(timedelta()),
        ),
    )

但正如我所说，我希望在这个月和活动持续时间之间得到交集。它可行吗？

Answer 1

试试这个

from datetime import datetime, timedelta
from django.db.models import Sum, F, DurationField

start_time = datetime.now() - timedelta(days=30)
end_time = datetime.now()
Event.objects.filter(started_at__gte=start_time, ended_at__lte=end_time, other_filter).annotate(
    time_diff=F('ended_at') - F('started_at')).aggregate(sum_time_diff=Sum('time_diff', output_field=DurationField()))

用过滤器注释timedelta和

1 个答案: