Does `include IdentityCache` automatically cache the model its included in?

I have a model where I'm including IdentityCache, let's call it Foo. I don't necessarily want this model and all of its attributes cached, but I do want its relationship cached. I have a relationship defined like:

cache_belongs_to :thing

The cache works just fine for doing things like calling foo.fetch_thing, but I noticed that when an attribute for the Foo model is updated, I get logging that looks like:

[IdentityCache] expiring=Foo expiring_id=2342 ...

and then more output saying that a delete failed for IDC:7:blob:Foo:....
So I guess my questions are:

• By including the module, is Foo and its attributes being stored into cache whenever its called?
• Any ideas why a delete failed would be consistently called when updating one of Foo's attributes?
• Is there a way to prevent Foo from being cached (since I only want it's association to be cached)?

Start by tracing the IdentityCache module inclusion and the cache_belongs_to relationship behavior described in the issue. Reproduce an attribute update on Foo and inspect the resulting expiration and delete-failed logs; the work is done when the caching behavior, deletion failure, and possibility of association-only caching are explained.