[ZODB-Dev] Proposal: cross database reference seat belt

[Shane Hathaway]

Jim Fulton wrote:
> Thanks for writing this up!
> 
> Do we really need per-object control?
> 
> It would be simpler to simply allow or disallow (new) cross-data  
> references at the database level.
> 
> I think the most common use case for cross-database connection  
> limitation is support for "mounts".  With mounts, there are a small  
> number of direct references between databases.  This could be  
> addressed by instantiating a database in a mode that allows cross- 
> database references and using that instantiation to establish the  
> mounts. All other instantiations would disallow new cross-database  
> references.
> 
> Do you have a specific use case that requires _p_check_xref?

No.  Good point.

I am hoping that even after we configure the system to disallow new 
cross-database references, we can still make other modifications to the 
objects that contain cross-database references.  For example, if I have 
a site object containing a catalog in another database, I should still 
be able to modify the title attribute of the site, as long as I don't 
try to change the catalog.

Shane