[Zope] Object without Undo?

[Terry Hancock]

Hi All,

I'm creating an "infinite-set" type product which generates
objects on-the-fly based on their URL. In general many
more objects are possible than are reasonable to store,
yet relatively few would be used at any one time. Hence,
a sensible approach is to provide a cache of recently
requested objects and serve from the cache whenever
feasible.

After several design iterations, and one (mostly) working
model, which unfortunately didn't scale too well, I've
decided on actually inheriting from "ObjectManager" and
storing the objects in the main object. As objects expire
from the cache, they are deleted.

However, with the way Zope's database works, I have to
wonder if I'm actually acheiving anything -- the deleted files
are still taking up space until the database is packed!

So, I'm wondering if (via Zope's API, as this is a Python-based
product), there's a way to mark an object as not undoable --
i.e. when it gets deleted, it's really gone.

The alternative would seem to be to pack the whole database
frequently.  Which is what I'll do if there's no other way.

It appears that I can get the desired behavior by overloading
the _getOb() method of ObjectManager and catching the case
of a request for a non-existent object -- if it happens, I just
call the code to make the object, add it with _setObject()
and then let _getOb() continue with the request, which should
now succeed.

I presume this would make the cached object visible to
Zope calls in all the usual ways (e.g. URL: "parent/cached_obj",
Python: "parent.cached_obj", etc).  My previous implementation
used __getattr__() directly and only worked for the URL
approach.

Any comments or ideas appreciated, thanks!

Terry

-- 
------------------------------------------------------
Terry Hancock
hancock@anansispaceworks.com       
Anansi Spaceworks                 
http://www.anansispaceworks.com 
P.O. Box 60583                     
Pasadena, CA 91116-6583
------------------------------------------------------