[storm] why weakrefdict for cache?

[Bernd Dorn]

On 31.08.2007, at 14:57, Christopher Armstrong wrote:

> On 8/31/07, Bernd Dorn <bernd.dorn at lovelysystems.com> wrote:
> we use storm with zope (version .10) and discovered that the
> store._cache attribute never caches, because the weakrefs are gone
> immediatly
>
> Your conclusion is incorrect. The cache does work as intended;  
> perhaps it is not what you want, though. The cache is there to  
> prevent loading objects from the database when they are already in  
> memory, and to avoid creating duplicate objects when the same row  
> is loaded twice (if a row is retrieved a second time within the  
> same transaction, the original object is updated instead of  
> creating a new one).

hm dunno if i understood you right ... the point is that i don't want  
to retrieve the row again

if i do a store.get(Klass, id) and i don't reference the object  
anymore in my code it is gone immediatly

then i do the same get one more time, storm does a select again

i don't understand the use-case for this kind of caching - if i have  
to maintain  a reference to the object anyways, why do a need the cache?

for example:

we have a request in zope and i want to get a specific storm object i  
have to get it via storm.get(...)

in the same request/transaction i do a second get, from another  
component of my view and i also have to use storm.get(..) for it

so we end up having up to 30 ident selects to the database for a  
single page

i am wondering how this is handled in launchpad





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