[ZODB-Dev] URGENT: ZODB down - Important Software Application at CERN

[Jim Fulton]

Well said. A feature I'd like to add is the ability to have persistent  
objects that don't get their own database records, so that you can get  
the benefit of having them track their changes without incuring the  
expense of a separate database object.

Jim


On May 26, 2009, at 11:48 AM, Chris Bainbridge wrote:

> 2009/5/26 Pedro Ferreira <jose.pedro.ferreira at cern.ch>:
>
>> In any case, it's not such a surprising number, since we have ~73141
>> event objects and ~344484 contribution objects, plus ~492016   
>> resource
>> objects, and then each one of these may contain authors, and fore  
>> sure
>> some associated objects that store different bits of info...
>
> I had a similar problem packing a large 15GB database. This may sound
> obvious, and is totally application specific, but you might like to
> look into whether it really is necessary to have so many individual
> ZODB objects. I found that often I would have a class that inherited
> from one of the Persistent classes that was part of a larger
> Persistent class, resulting in an explosion of Persistent objects. It
> was possible to make many of them non-Persistent, so that they only
> get serialised and stored in the database as part of whatever larger
> Persistent object that they're part of. Another thing to watch out for
> is dangling pointers - given the dynamic nature of Python, it's very
> easy to leave a pointer hanging around to an old Persistent object
> that you don't really need to store in the database, which in turn
> points to more objects, etc. Any object that can be reached in a
> traversal of the object graph will be kept in the database forever.
> The lack of a formal schema and rigid type checking make these kind of
> errors much easier to make, and with today's hardware they don't
> become a problem until the database grows big.
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--
Jim Fulton
Zope Corporation