[Zope-dev] Question about _v_ attributes and database connections

[Chris Withers]

Hi Marco,

Marco Bizzarri wrote:

> We're trying to tackle a problem in hanging connections in ZPsycopg.

Hehe, I fixed this for ZOracleDA a couple of months ago. You may want to look at 
the thread pool code in there to see how I did it, gimme a nod if you need a URL 
(it's on a CVS branch in cvs.zope.org)

> However, I would like to have some information about the functioning of
> the _v_ attributes, and the cache management. In particular:
> 
> 1) where is the code which handles the _v_ attributes (I like to look at
> the source code, you know ;))

Never bothered finding it, the sematics are pretty well documented.

> 2) where is the code which handles the caching of the objects?

The ZODB cache. It's big and complicated, trust me, you DON'T need to go there...

> 3) is it possible to disable caching of some object?

No. The fact that you want to means you're mis-using _v_ attributes ;-)

> 4) when an _v_ attribute is removed, what code of the object/attribute
> itself is called?

None. I believe it gets lost at the object is ghosted.

> If possible, please answer also directly to me (I'm not on this list).

Are you maintaining ZPsychopg? If not, the maintainers might be able to help...

cheers,

Chris - who learnt a whole lot more about ZODB and ZODB caching when solving 
this kind of problem in ZOracleDA ;-)

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