[ZODB-Dev] Migrating classes in ZODB 3.5.1

[Syver Enstad]

Tim Peters wrote:

>[Tim Peters]
>  
>
>>>>Stephan Richter was wrestling with a migration script a couple months
>>>>ago. I don't know whether he packaged the code he ended up with for
>>>>reuse. Here's a record of the IRC chat in which details got worked out:
>>>>
>>>>   http://zope3.pov.lt/irclogs/%23zope3-dev.2005-08-25.log.html
>>>>        
>>>>
>
>[Stephan Richter]
>  
>
>>>The resulting code from the discussion is publically available in the
>>>SchoolTool source:
>>>
>>>
>>>      
>>>
><http://source.schooltool.org/viewcvs/trunk/schooltool/src/schooltool/genera
>tions/evolve5.py?rev=4984&view=auto>
>
>[Syver Enstad]
>  
>
>>Thank you Stefan. I am right if I suppose that the reason this fixes all
>>references is that it saves all persistent objects in the database?
>>    
>>
>
>Basically, but read the IRC log for details:  it (re)saves the current
>revision of all objects not in a version.  It does not change non-current
>revisions of objects, nor any revisions of objects in a version.  This is
>because the FileStorage iterator only knows about current non-version
>revisions.
>
>  
>
I don't use versions so that's fine. The IRC log was very illuminating 
BTW. It seemed to basically be going through exactly the same issues 
that I have been going through.

>>Will this also fix references to persistent objects in non persistent
>>objects stored in the database?
>>    
>>
>
>If (and only if) they're reachable from the root object following a chain of
>non-version current revisions.  You can't store a non-persistent object N
>directly in ZODB -- the only way N can get in is by being attached to a
>persistent object P.  Then N's entire state is included in the pickle for P.
>So when P is (re)saved, the entire state of N is recomputed, including (of
>course) all references to persistent objects (if any) contained in N.
>
>
>  
>
I see, that sounds good to me.

For now I am basically one happy guy. Thanks to everyone for responding 
and helping me out with my problem migrating.