[Zope3-Users] Advanced usage of Z3 schemas...

[Gary Poster]

On Oct 3, 2005, at 4:45 AM, Andreas Jung wrote:

>
> Hi,
>
> I am currently thinking about for a new version of PloneCollectorNG  
> based on Zope 3. The currently implementation uses per-instances  
> schemas (acquired from a parent object managing the schema). How  
> would you do that in Zope 3?

It sounds like you want persistent schemas.  Although there is some  
code in Zope 3 going in that direction, to my knowledge it does not  
work right now.

> Another question: in Zope 3 we have FieldProperties that  
> automatically handle setting and getting values. This  
> implementation stores the values as instance attributes. What would  
> be the recommended way to store attributes in a RDBMS instead  
> inside the ZODB? By introducing a new RDBMSFieldProperty that  
> handles the set/get methods in the same way as the FieldProperty  
> implementation?

That might be one way of doing it.  You'd have to have a unique key  
for the object in the RDBMS; maybe an intid would be the way to  
look.  It might get a little bit tricky, as relying ion intids means  
that you start requiring that your object be placed in the ZODB  
before you set the attributes.  I'd be tempted to look for approaches  
already working in the field.

So, alternatively, you might want to look at APE for the RDBMS side  
of things, so that your code just puts attributes on the object, and  
the storage is responsible for the RDBMS side.  A third approach  
might be http://codespeak.net/z3/sqlos/.

Gary