playfire / django-cache-toolbox Goto Github PK

Let's say I have a Person object with a ForeignKey to a default image.

class Person(models.Model):
    default_image = models.ForeignKey('people.Image', blank=True, null=True,
         on_delete=models.SET_NULL)

class Image(models.Model):
    some_image_field = models.ImageField(...)

>>> p = Person.objects.get(first_name='Phil')
>>> img = Image.objects.get(**some_kwargs)
>>> p_cached = Person.get_cached(pk=p.pk)
>>> p.default_image = img
>>> p.save()
>>> p_cached = Person.get_cached(pk=p.pk)
>>> p.default_image is not None
True
>>> p_cached.default_image is not None
True
>>> img.delete()
>>> p.default_image is None
True
>>> p_cached = Person.get_cached(pk=p.pk)
>>> p_cached.default_image is None
Traceback (most recent call last)
...
File "django/db/models/fields/related.py", line 316, in __get__
rel_obj = QuerySet(self.field.rel.to).using(db).get(**params)
DoesNotExist: Image matching query does not exist.

It's a pretty tricky bug, and it may be nearly impossible to fix if the on_delete actually sets a database property that leads to that behavior rather than doing it in Python.

Nonetheless, I felt I should probably report it just so it's a known issue.

Hi there!

Great work on this project. It looks like the commits have been coming fast recently, and I realize you say support for ForeignKey fields is planned, but I just wanted to put a ticket in to ping you about that.

ForeignKey support would be a great feature and would significantly decrease db hits for me.

The scaling isn't that important for me yet, so I probably won't be able to commit any time to helping out with this feature in the immediate future, but once we go live if this is a bottleneck I'd certainly be happy to work on this.

Thanks!

The db origin of an instance isn't set for objects retrieved from the cache, which means they can't usually be used against as ForeignKey/ManyToMany fields.

How about serializing the FileField to the relative file name?

this should at very least be in the documentation if you don't plan on fixing it soon

edited:
actually that doesn't seem right at all, the issue i'm seeing is when the primary key of the related object is out of sync with the parent object