在Django模型记录上实现TTL的方法是什么？

from django.db.models.signals import pre_save
from django.dispatch import receiver
from datetime import datetime, timedelta

from django.db import models

class MyModel(models.Model):
    created_at = models.DateTimeField(auto_now_add=True)
    # 其他字段...

@receiver(pre_save, sender=MyModel)
def check_ttl(sender, instance, **kwargs):
    ttl = timedelta(days=7)  # 设置TTL为7天
    if instance.created_at + ttl < datetime.now():
        instance.delete()

from datetime import timedelta

CELERY_BEAT_SCHEDULE = {
    'check_ttl': {
        'task': 'myapp.tasks.check_ttl',
        'schedule': timedelta(hours=1),  # 每小时触发一次
    },
}

from celery import shared_task
from django.db.models.signals import pre_save
from django.dispatch import receiver
from datetime import datetime, timedelta

@shared_task
def check_ttl():
    from myapp.models import MyModel
    ttl = timedelta(days=7)  # 设置TTL为7天
    records = MyModel.objects.filter(created_at__lt=datetime.now() - ttl)
    records.delete()