Memory Leak - Redisco doesn't delete filter keys properly

[kiddouk]

Considering the following code :

class A(models.Model):
   att = models.Attribute()

class B(models.Model):
   a = models.ReferenceField()

a = A()
a.att = "test"
a.save()

b = B()
b.a = a
b.save()

B.objects.filter(a_id=a.id)
# Here redis doesn't delete the filter keys as "_expire_or_delete" should. Leaking 2 more keys in the DB.

Redisco end up leaking 2 filter keys (best case) and n filtering keys in case of multiple filtering.

Suggestion

give a timeout to each temporary keys to let say 60 seconds. It will give time to the operation to succeed and let redis handle the clean up for us.

[kiddouk]

Moreover, issuing an EXPIRE command is as costly as ISSUING a DEL command and reduces the logic inside redisco.

[kiddouk]

This fix has obviously some implications:

You can't use your modelset for more than a minute. example :

cool_users = User.objects.filter(name="Jakub")
# wait one minute
len(cool_users) == 0
# True