[elephant-devel] Class Evolution

[Dan Knapp]

   Internally, Elephant stores a list of the slots in each object, by  
their names.  So, the new slot will be unbound in the existing  
objects - you can check using slot-bound-p.  If you delete a slot,  
the old values for objects that had it will still be in the database,  
but they will be harmless.  New objects will always be stored  
according to the definition that's loaded at the time.  If you want  
to rename a slot, you'll have to write migration code to copy  
everything from the old slot to the new one.

-- Dan Knapp

On Dec 29, 2005, at 1:47 AM, Waldo Rubinstein wrote:

> Is Elephant friendly with class evolution? For example, if I create  
> a CLOS object with, say 5 fields, and store some instances in an  
> elephant DB and then the CLOS definition of the class changes to  
> add a sixth field. What will happen to the existing five objects  
> when retrieved? Will new objects be stored with the new field  
> definition?
>
> Thanks,
> Waldo
>
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