5分钟后自动删除对象 [英] Delete an object automatically after 5 minutes

问题描述

我正在尝试创建一个在发布5分钟后自动删除对象的功能.

I'm trying to create a function that automatically delete an object after 5 minutes from publication.

from django.contrib.gis.db import models
from django.utils import timezone

import datetime

class Event(models.Model):
    name = models.CharField(
        max_length=100,
        )
    publishing_date = models.DateTimeField(
    default=timezone.now,
    blank=True,
    )

    @property
    def delete_after_five_minutes(self):
        time = self.publishing_date + datetime.timedelta(minutes=5)
        if time > datetime.datetime.now():
            e = Event.objects.get(pk=self.pk)
            e.delete()
            return True
        else:
            return False

问题是所有对象都被删除，而不仅仅是我想要的对象.

The problem is that all objects are deleted and not only the objects that I wish.

推荐答案

您应该交换比较，所以:

You should swap the comparison, so:

if time < datetime.datetime.now():
    # ...

或者更具可读性:

if self.publishing_date < datetime.datetime.now()-datetime.timedelta(minutes=5):
    # ...

因为这意味着现在现在前五分钟仍在发布 Event 的时间之后.

since this thus means that five minutes before now is still after the time when the Event was published.

话虽这么说，最好不要删除这些值，或者至少不要立即删除这些值，而要创建一个仅隐藏"这些对象的管理器.然后，您可以稍后定期删除元素.

That being said, it might be better not to delete the values, or at least not immediately, but make a manager, that simply "hides" these objects. You can then later, periodically, remove the elements.

我们可以通过以下方式聘请此类经理:

We can make such manager with:

from django.utils import timezone

class EventManager(models.Manager):

    def get_queryset(self):
        return super().get_queryset().filter(
            publishing_date__gte=timezone.now()-timezone.timedelta(minutes=5)
        )

，然后使用此管理器，例如:

and then use this manager like:

class Event(models.Model):
    # ...
    objects = EventManager()

然后， Event.objects 将仅检索不到五分钟前发布的 Event .

Then Event.objects will only retrieve Events that have been published less than five minutes ago.

您可以使用以下方法定期删除此类事件:

You can periodically remove such events with:

Event._base_manager.filter(
    publishing_date__lt=timezone.now()-timezone.timedelta(minutes=5)
).delete()

这将删除批量"中的这些 Event .

This will then remove these Events in "bulk".

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