[ZODB-Dev] Fixing POSKeyErrors :-)

[Jim Fulton]

On Feb 14, 2008, at 7:21 AM, Binger David wrote:

>
> On Feb 13, 2008, at 11:28 PM, Paul Winkler wrote:
>
>   (Jim wrote)
>>> Catalogs and session data change much faster than content.  It  
>>> makes sense
>>> to pack these more frequently.  On large system, it provides the  
>>> ability to
>>> spread load over multiple servers, if necessary.
>>
>> Also, as I understand it, you can get more benefits from the "regular
>> content" ZODB cache if you're not constantly moving tons of catalog
>> data through it, so there's a performance win
>
> It seems like all of these potential advantages are available through
> the use of multiple storages, but none of them really require  
> database-level
> support for cross-storage references.    On the other hand, it seems
> clear that cross-storage references make the system as a whole
> (software + people) less reliable.

I don't agree in general.

> Perhaps I misunderstand, but low-level cross-site references seem  
> like "secret"
> weakrefs.  Maybe we'd be better off if they were explicit, higher- 
> level objects,
> used and dereferenced intentionally where required.


I don't object to this approach. I'll note that we had an approach  
like this before for Zope (mounts) and it had plenty of disadvantages  
of it's own, including injecting Zope-specific code into ZODB.

If someone can make something like this work without modifying ZODB, I  
won't object.

I think it would be easier to make the current multi-database approach  
a bit more explicit.  I'll probably do that.

Jim

--
Jim Fulton
Zope Corporation