[Zope-dev] Experiments with ORMapping

[John D. Heintz]

I think this is a great idea!  I would definetely like to use and contribute 
to this effort.  Having this kind of flexibily would be fantastic.

After demonstratable Python code is working I would request that usability 
issues (UI Schema mapper, data migration/schema evolution tools, ZEO 
integration, multi-Storage uses) be addressed sooner than later.  

John

On Monday 14 May 2001 10:47, Shane Hathaway wrote:
> Chris Withers wrote:
> > Shane Hathaway wrote:
> > > I'm telling you there's a lot more you can do with the code that makes
> >
> > <snip>
> >
> > > The next thing to do is to write a fishbowl proposal.
> >
> > This sounds cool but made my head hurt :-S
> >
> > Can you try and bring this back down to the level of us mere mortals by
> > explaining how your OR stuff would let me take a table of data in an
> > RDBMS table and have it appear as objects in the Management Inteferace?
>
> Sorry, this is at a pretty low level and I do need to explain it better.
>
> One would define an "ObjectMappingSchema" whose job it is to store and
> retrieve objects of a specific type and in a specific location.  It
> would usually grab a database connection object to do its work.  When
> loading, it would perform a query then manually put attributes into a
> persistent object.  When storing, it would grab specific attributes from
> the persistent object and execute a statement to store those attributes.
>
> So let's say you want a ZODB to store and retrieve users in a specific
> table while putting everything else in pickles.  You would create an
> instance of PickleSchema, which implements the ObjectMappingSchema
> interface, and tell it to manage everything *except* the users mapping
> in BasicUserFolder objects.  You would tell it to store and retrieve
> this object using your UserFolderSchema instead.  Your UserFolderSchema
> would store and retrieve the users from the USERS and USER_PREFS
> tables.  The user table wouldn't require the use of OIDs but would
> require unique user IDs.
>
> So in the management interface nothing would change.  Nor would the
> application-level Python code.  You would only define a layer that maps
> objects to a relational database.  You would still see the user folder
> as you do now.
>
> Now, it may be useful to provide a management interface for defining the
> schema mapping.  I haven't approached that yet; AFAICT this is where the
> work done on SmartObjects and DBObjects would be very useful.  Initially
> I was planning for people to code the mapping purely in Python so we
> could gain experience and find common patterns before inventing a UI.
>
> Shane
>
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John D. Heintz | Senior Engineer

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