[ZODB-Dev] Fixing POSKeyErrors :-)

[Chris Withers]

Jim Fulton wrote:
> 
>>> It's a shame ZODB doesn't turn POSKeyErrors into proper Broken objects
>>> as it does when the class can no longer be imported. The problem with
>>> POSKeyErrors is that they prevent you accessing *any object that refers
>>> to the broken object* not just the missing object itself. This means
>>> that when objects *do* go missing, the data loss can be much much worse
>>> than it needs to be.
>>>
>>> What does everyone else think?
> 
> I think you are right and this should be treated as a bug.

Okay, so I count two issues:

- packing and multiple mounted storages
- POSKeyErrors resulting in failure to load referring object rather than 
creation of a broken referred object

Where would you like me to file these bug reports?

>> I'm not sure the situation is as bad as you're suggesting, since I
>> vaguely recall that inter-object references encode the class of the
>> referenced object, allowing a parent to load even if its child is gone.
> 
> I'm not sure if this is the case for cross-database references. I don't 
> remember the details.  Even if it isn't, we should probably create a 
> broken object rather than giving a POSKeyError.

That would certainly aid minimising data loss create by the first and 
any other POSKeyError-causing bugs ;-)

cheers,

Chris

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