[ZODB-Dev] Fixing POSKeyErrors :-)

[Chris Withers]

Christian Theune wrote:
>> - specify in policy that cross storage references should result in the 
>> target object being copied to the storage
> 
> I think the semantics to that aren't as obvious as they seem. This can 
> go bad regarding consistency when multiple cross-database reference from 
> various databases refer to the same object resulting in copies, then the 
> copies can get out of sync.

Sometimes having the transparency offered by ZODB is a bad thing. Would 
be nice if there was some way to say whether:

obj.a = a

...means "move obj to the same storage as a and replace reference in any 
databases with cross-storage references to obj's storage" or "create a 
cross-storage reference to a in obj's storage".

> A gut feeling I have about the situation is that we get bitten by the 
> fact that features in the ZODB don't behave as orthogonal as we'd 
> expect/like them to be.
> 
> The implementations of different features (like packing and undo) 
> influence the outcome of other features that were not anticipated.
> 
> Does it have to be true that we have to worry about the full cartesian 
> product of all possible states of all features? This seems like a risk 
> for the long run and a chance for the long run to get this right.

Indeed.

I think we need to agree what features "zodb" offers and make sure 
they're tested for some "full set of supported operations"...

cheers,

Chris

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