CODEWITHSUNDEEP
django
zmbq
zmbq

Reputation: 39069

Django default caching of foreign key models

For the life of me I can't find the answer to this question online, although it's a basic one.

I have two models, one referencing the other:

class A(models.Model):
    name = models.CharField(...)
    ...

class B(models.Model):
    a = models.ForeignKey(A)

Now, I'm keeping an instance of B in memory, and ever so often I access b.a.name . Does accessing b.a.name cause a database query every time, so that changes in a.name (changes done by another process) are seen in my process? Or do I have to query a explicitly each time?

Upvotes: 0

Views: 331

Answers (1)

Daniel Roseman
Daniel Roseman

Reputation: 600059

I'm surprised you haven't been able to find any information on this. It's fairly well documented that forward relationships are cached on first usage - what happens is that a cache attribute is created, and subsequent lookups will check this first.

So yes, this means that changes to that object in another process will not be seen, and you will need to re-query each time. (Note also that depends on your database's transaction isolation setting, you might not even see the new value on re-querying - you may need to commit the current transaction first.)

Upvotes: 1

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