[Zope3-dev] Re: zope.app.rdb bug?

[Jeff Rush]

David Johnson wrote:
>>
> In regards to persistence, are we saying this problem occurs when the
> connection is an attribute of a persistent object? In our case the
> connection resides in a persistent object but is called and used in a
> non-persistent one.

It doesn't matter if the 'caller' of the connection is persistent or not, but 
that the connector is itself a persistent, local utility stored in the site 
manager folder.

 > Specifically, we're using the connection in a
> non-persistent shopping cart object.  Upon initialization the cart object
> retrieves the connection from a persistent parent in the context in which
> the cart is initialized. In this way, different shopping cart items can be
> stored in different databases depending upon the container.  The parent is
> essentially a copy of ISQLScript. 

I copied SQLScript as well.  Be sure that on each SQL operation you re-fetch 
the connection object using the connection name.  Do not hold on to the 
connection object itself, as it may change during system re-configuration.

Here is my calling method:

     def invoke_SQL(self, query):

         cache = getCacheForObject(self)
         location = getLocationForCache(self)
         if cache and location:
             _marker = object()
             result = cache.query(location, {'query': query}, default=_marker)
             if result is not _marker:
                 return result

         try:
             connection = zapi.getUtility(IZopeDatabaseAdapter,
                                          self.connection_name)()
         except KeyError:
             raise AttributeError, (
                 "The database connection '%s' cannot be found." % (
                 self.connection_name))

         result = queryForResults(connection, query)
         if cache and location:
             cache.set(result, location, {'query': query})
         return result

Notice the zapi.getUtility() call to re-fetch each time.

-Jeff