[Zope3-dev] Re: Replacing class refs in ZODB

[Jim Fulton]

Derrick Hudson wrote:
> On Fri, Feb 18, 2005 at 11:59:04AM -0500, Jim Fulton wrote:
> | Garrett Smith wrote:
> | >Jim Fulton wrote:
> | >>Garrett Smith wrote:
> | >>
> | >>>Rather than leave aliases around forever, is there a utlity (or other
> | >>>means) one can use to update references to renamed/moved classes in
> | >>>the ZODB?
> | >>
> | >>Not currently.  We'd like a cleaner mechanism, but haven't come up
> | >>with one yet.
> 
> | >So I take it this is non-trivial. I was hoping it would boil down to a
> | >search-and-release in the Data.fs.
> | 
> | It depends on what "this" is.  One could fairly straightforwardly
> | write a script that could convert an off-line database.  I think we
> | really want to be able to do this without taking the database off-line.
> 
> I tried to do this as a step to solve a problem I had about two weeks
> ago.  It didn't work, though.
> 
>     #!/usr/bin/python2.3 -i
> 
>     from ZODB import FileStorage, DB
>     storage = FileStorage.FileStorage( 'Data.fs' )
>     db = DB(storage)
>     conn = db.open()
>     root = conn.root()
>     app = root['Application']
> 
>     import zwiki, zwiki.wiki
>     # setup the alias for the initial load
>     sys.modules['zope.app.wiki'] = zwiki

This was too late.

>     the_wiki = app.data['the_wiki']
>     the_wiki.__class__ = zwiki.wiki.Wiki

This isn't necessary.  It would have gotten the new class
via the alias.

>     the_wiki._p_changed = True

This is all that was needed to get the wiki object
itself written. Subobjects of the wiki object would be
unaffected.

>     # save the changes:
>     import transaction ; transaction.commit()
> 
> The ZODB (probably pickle, actually) would complain that it didn't
> like the object.  I think it is because I changed the class, so some
> sanity check failed. 

No, it's because you set the alias too late.

Jim

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