[elephant-devel] Class Evolution

[Waldo Rubinstein]

Thanks Robert.

I will write some test cases and see how it behaves. I just wanted to  
know before I spent the time to do it :)

Thanks,
Waldo

On Dec 30, 2005, at 10:46 AM, Robert L. Read wrote:

> The best way to answer this question would be to look at, or write  
> some new, tests.
>
> I evolve classes all the time, and have never noticed a problem, at  
> least if you add
> a slot that is not required at object construction time.   
> Obviously, it is possible to add
> a slot in fact needed for the object to be wholesome, and elephant  
> can't make something
> up in such a case.
>
> In one case I think I actually wrote a little code to:
>
> (map-btree #'(create-and-store a new object of class X) (all- 
> objects of class Y))
>
> That will always work if you have a class evolution that you just  
> can't get around
> any other way; that is the basic strategy behind inter-store  
> migration.
>
> So I agree with Ben:  it basically works, probably has glitches if  
> you do something
> complicated, but there is, by writing enough (relatively simple)  
> code, always a way out.
>
>
>
> On Thu, 2005-12-29 at 11:52 -0600, Ben wrote:
>> it should be relatively class friendly.  it should even support fancy
>> stuff like change-class.  there's talk about this in the  
>> documentation
>> somewhere...
>>
>> B
>>
>> On 12/29/05, Waldo Rubinstein <waldo at trianet.net> 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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