[Zope-DB] Re: Cache Controlled SQL methods (CCSQLMethod)

[Dieter Maurer]

Godefroid Chapelle wrote at 2003-1-17 12:18 +0100:
 > I need to be able to flush cache for almost RO ZSQL methods.
 > 
 > Searching the web brought me to Cache Controlled SQL methods (CCSQLMethod) 
 > http://www.dieter.handshake.de/pyprojects/zope/CCSQLMethod.html
 > 
 > I saw that the product is quiet old.
 > 
 > Does that mean that
 > 
 > - it's robust enough that id did not need to be patched later and I can use 
 > it safely in production ?
It is still used in a production system.
HOWEVER: this is a Zope 2.1.6 installation, which means it is ancient.

I never tried to port it to newer Zope versions (because I switched
employer in between and did not have a need for cache controlled
Z SQL Methods in the mean time).

I expect, the only thing that might be needed are some security
declarations for the cache control API.

I think (though do not know for sure) that the underlaying base
module "SharedResource" is still used by some persons.

 > - it's design was flawed enough that it is not used anywhere ?
You must not ask me ;-)
I made the design...

 > or are there best ways to control ZSQL methods cache that came out later ?
I am meanwhile convinced that there is a ZODB method that allows
to invalidate all versions of an object in any cache (this would clear
the "_v_" variables that hold the cache).

I did not yet look what this method is, but I may do so soon,
because we currently face a non-deterministic session problem.
With high probability, it is caused by the manipulation of
deeply structured session data without telling the session,
that is was changed.
I plan to hunt this problem by forcing the session object from
the ZODB cache at the end of the request (transforming the
non-deterministic problem into a deterministic one).
In this endeavour, I will carefully study the ZODB and its cache
mechanism.

I will start with the ZODB documentation (--> Zope.org)
and, if not sufficient, go down into the sources.

Of course, you can do the same ...

 > I am not tech savyy enough to evaluate myself :-(
Then, you may need to wait some time.
Or ask in the mailing list (best probably, the ZODB-dev mailing list).


Dieter