[Zope] Philosophical question - Zope Objects vs Entities in a RDBMS

[Jim Fulton]

Rowan Hick wrote:
> 
> Okay so I'm getting into this whole Zope deal, and from what I have seen
> so far it looks pretty darned good, I like the OO concept, but with it
> it poses a few design issues for websites / web applications
> 
> Traditionally all data is stored in some form of relational database,
> and then the scripts pull it back out again. Now we all know and hate
> relational databases (well I do anyway as I'm a child of the information
> age - learning in OO concepts and then having to go back to a relational
> database) but they are remarkably good for what they do - storing large
> amounts of data and allowing you to retrieve it in a quick and
> relatively painless manner, if you get your head around SQL.
> 
> Now Zope comes along with the ability to create and persist objects
> without the need for a relational database. Wooohooo... all my prayers
> have been answered, or have they?.
> 
> Q1. Has anyone tried to build webapplications with large (maybe into the
> 10's of thousands) numbers of Zope objects?

Yes, although I suspect some people wouldn't consider this large.

> Q2. How much more or less efficient is Zope for storing a piece of data
> over a traditional relational database ?

That's an interesting question.  It depends on alot of things, such as
the indexes used in the RDBMS, or even what RDBMS you use. I imagine
that ZODB and RDBMS are similar in the storage required, although it
would be interesting to do a comparison with some sample data.

> Q3 (I'm a newbie here) Can a python external method access Zope objects
> ?  Eg if I create a task object from a ZClass can I then do things with
> it from a python script?

Yup.

> Q4. I think I remember seeing a post about the Zope database being a
> single large file posing problems with the Linux filesystem.. or was
> that the windows filesystem.. if so then that could limit Zope's
> potential in a commercial production enviroment, surely ?? If this is
> true what have people done to try and get around this, ie archiving
> objects (however that could occur) etc.. ?

A very important thing to note is that ZODB has an *open* storage 
interface.  You can plug in (with a fairly small amount of Python code)
any storage manager you want.  The default storage manager that comes with
Zope uses a single file. This storage manager is a resonable default but
might not be best for everyone.  Ty Sarna has written a BDB storage
manager, and it's only a matter of time before someone writes an RDBMS
storage manager.

The approach of puting data in a single file is a feature of the 
FileStorage, it is not a feature/limitation of ZODB.

Here's a bonus question:

Q5. I really need to store my data in an RDBMS, can I integrate it
    with Zopes objec't system and get some of those nify OO benefits.

Good question. ;) You sure can.  Zope SQL methods return objects, not
just rows. The objects returned support acquisition, can particpate in
URL traversal, can have DTML and other forms of methods, etc.  In Zope 2.2, 
you'll even be able to define ZCLasses (Zope classes) for relational
data.

> Thanks in advance for any responses,

No problem.

Jim

--
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