[BlueBream] [Zope-dev] Reg. persisting data in ZODB via forms

Marius Gedminas marius at gedmin.as
Wed Jun 8 13:40:56 EDT 2011

On Wed, Jun 08, 2011 at 06:20:26PM +0530, Joe Steeve wrote:
> As I mentioned on a follow-up post, we figured the 'Persistent' part. :)
> On Wed, 2011-06-08 at 13:29 +0100, Laurence Rowe wrote:
> > My guess is that the ObjectModifiedEvent is dispatched to your
> > object's parent and causes something to change there, with the side
> > effect of storing your updated object.
> Even if the object's parent (a btree-container) had changed, will it
> attempt to force-store its entire child-tree? I am trying to imagine the
> effect of it on a huge tree.

The smallest unit that is ever written to a ZODB is one persistent object
(with all its nonpersistent attributes/items, recursively).

BTrees use multiple persistent buckets for their state and are very
efficient, storage-wise.  But this only matters when you're
adding/removing items to a BTree.  If you're modifying a persistent
object stored in a BTree, the BTree itself remains unmodified and does
not need to be re-written 

Marius Gedminas
Linux became only possible because 20 years of OS research was carefully
studied, analyzed, discussed and thrown away.
		-- Ingo Molnar
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