Why can't or shouldn't I just hash the address of an object? And how.

[Enjoys Math via Digitalmars-d-learn]

I am creating a custom graph database for our app. It holds not 
one huge graph but a collection of independent graphs.  I would 
like to be able to delete them without looping through a range of 
billions of Graph class references.

How can I accomplish this with an AA and hasing?
Is it:

typeof(T).getHash(&o)?

Or does that do something other than just get the address?

Is this a bad idea for an App communities main content server?