Caveat to this below.
On Mon, Jul 15, 2013 at 7:54 AM, Marius Gedminas <mar...@gedmin.as> wrote: > On Mon, Jul 15, 2013 at 03:36:21PM +0200, Pedro Ferreira wrote: > > We need to move a considerable number of persistent objects (~40K) from > > one module to another, and we were wondering what is the best strategy > > to follow. > ... > > Has anyone ever done anything like this? Which approach have you > > followed? Any suggestions? > > 1. Make sure all the classes are still importable from the old location > ('from newmodule import MyPersistentSomething # BBB') > > That is sufficient to make it work. If you also want to eradicate all > references to the old module name from your ZODB (e.g. because you'd > like to remove the BBB import), then proceed to step 2: > > 2. Write a script that loads every instance of this class and does a > > obj._p_activate() # actually not sure this is required, but won't hurt > obj._p_changed = True > > and then commit the transaction. Do the commit multiple times, after > each batch of several hundred objects, to avoid excessive memory usage. > Also be sure to handle conflict errors and retry that batch if you're > running this script on the live system. Finding all instances is left > as an exercise for the reader (sometimes findObjectsProviding() helps, > if you use nested containers everywhere; sometimes application-specific > logic works best; sometimes you end up having to use ZODB iterators to > loop through every single object in the DB -- I believe zodbupdate does > that.) > This works only partially, AFAICT. It will update the stored class name of a persistent object. It will not seek out and change the class name of the object in a reference. Your step 3 (removing the BBB code) can break things (broken objects) as a result of this. Fixing persistent objects is half the battle if you get broken references to them. You can verify that this is incomplete by creating a PersistentMapping of some simple objects, perform the trick above, commit, then pack. You will still have the old BBB classname stored in the database in the references, unless you do a _p_changed=1 on the mapping containing/referencing the items as well (then commit). I am not sure how to walk/iterate all oids for all transactions to get all possible referencing objects (I assume this is storage-specific, maybe building a reference map like Lawrence Rowe has done ). This might be necessary to update the referencing objects?  http://plone.org/documentation/kb/debug-zodb-bloat/inspectZodbUtils.py Sean
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