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

[David Johnson]

Good. I think I'm clear. That procedure is exactly what I am following,
except I don't cache queries for this application.  My database connection
is a persistent utility.  I'll give the global utility a try.  

> -----Original Message-----
> From: Jeff Rush [mailto:jeff at taupro.com]
> Sent: Monday, April 17, 2006 9:27 AM
> To: David Johnson
> Cc: zope3-dev at zope.org
> Subject: Re: zope.app.rdb bug?
> 
> 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