ZODB, maintaining referential integrity

[Joe Steeve]

How to maintain "referential integrity" in a ZODB. Simply put: When an
object-A is removed from a container, the references to object-A, in
other objects should go invalid.

I tried holding a persistent.WeakRef whenever a reference was required.
However, the WeakRef seems to go invalid only after a GC on the db
(correct me if I am wrong).

The other approach seems to be to use IObjectWillBeRemovedEvent at the
site of the referencing object, to act accordingly.

How do other people deal with this?

--
Joe Steeve
HiPro IT Solutions Private Limited
http://hipro.co.in/

[Thierry Florac]

Hi,

Actually I handle this use case using IObjectRemovedEvent subscribers.

Can't see any other simple way...  :-/

Best regards,

Thierry

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[Chris Rossi]

The other approach would be to only store objects in one canonical place, and use references that just store the path to the object or the oid.

Chris

[Thierry Florac]

Hi !

I often use internal IDs (via an IIntIds utility) to store objects references.

The drawback of this method is that you have an indirection and you always have to check that the reference target is still available before using it!

So even in this use case I use an event listener to remove the reference when the target is removed...

Best regards,

Thierry

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[Joe Steeve]

On Thu, 2016-04-21 at 11:09 +0200, Thierry Florac wrote:
> Actually I handle this use case using IObjectRemovedEvent subscribers.
> Can't see any other simple way... :-/

I am taking this approach. Specifically I am using repoze.folder's
IObjectWillBeRemoved. Thanks :)