Le mardi 30 septembre 2014 13:28:16 UTC+2, Simon King a écrit : > > On Tue, Sep 30, 2014 at 8:52 AM, tonthon <tont...@gmail.com <javascript:>> > wrote: > > Hi, > > > > I'm using dogpile cache to store objects in a redis database, here's the > > sample function I use for my tests : > > > >>>> @region.cache_on_arguments() > >>>> def get_my_model(id): > >>>> return DBSession().query(Model).get(id) > > > > I retrieve models : > > > >>>> model1 = get_my_model(5) > >>>> model2 = get_my_model(5) > > > > model2 is retrieved from the cache. > > Since it's not attached to any session, when accessing a lazy-related > > object : > > > >>>> model2.owner > > > > I get a a DetachedInstanceError > > I found a turnaround : > > > >>>> DBSession().enable_relationship_loading(model2) > >>>> model2.owner > > > > that allows me to do what I want, but I'm not really satisfied with this > > design. > > > > Is it a clean way to go or should I review my caching strategy ? > > > > The normal approach is to use session.merge() to attach a cached > object to a session. Note that session.merge() actually returns a *new > instance* attached to the session - it doesn't attach the instance > that you passed in: > > http://docs.sqlalchemy.org/en/latest/orm/session.html#merging > > There's also a sophisticated example of using dogpile.cache at: > > http://docs.sqlalchemy.org/en/latest/orm/examples.html#examples-caching > > Hope that helps, > > Simon >
Hi, I didn't knew merge was supposes to be used in such a case, it works like a charm. Following that tip, I've added this decorator : >>> def cache_wrapper(func): >>> """ ensure a model returned from a cached function is attached to the current session """ >>> def cached_func_wrapper(*args, **kwargs): >>> obj = func(*args, **kwargs) >>> if object_session(obj) is None and has_identity(obj): >>> obj = DBSESSION().merge(obj) >>> return obj >>> return cached_func_wrapper So the cached function is like this one : >>> @cache_wrapper >>> @region.cache_on_arguments() >>> def get_my_model(id): >>> return DBSession().query(Model).get(id) I'll have a look at the examples you pointed. Thanks a lot for your answer, Regards, Gaston http://www.majerti.fr -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
