merging is usually what we recommend with caching, load=False is there to ensure no more SQL is emitted.
if the objects initially were persistent, and then cached, session.add() would put them right back in as persistent, but then they need to not be used in any other session, and they’d also conflict with any existing identities. that’s why merge is preferred. But the error you’re getting that the objects aren’t persistent is a little worrisome, though depends on how you are getting at these objects in the first place. Basically “persistent” means inspect(my_object).key is present. that’s the internal primary key that is assumed to have been used in the database. if it’s empty/None, then it means the object doesn’t represent a row in the DB. So an object that is cached and is presumed to represent a row in the DB should typically have a non-empty .key on the internal state. On Jan 14, 2014, at 5:59 PM, [email protected] wrote: > I resolved this by merging my cached instances into the session instead of > adding them. Does this have any negative side effects? It seems like the > right thing to do from the docs. Thanks Michael for your quick response. > > On Tuesday, January 14, 2014 5:48:55 PM UTC-5, Michael Bayer wrote: > > On Jan 14, 2014, at 5:44 PM, [email protected] wrote: > >> I have discovered something interesting... >> >> (Pdb) db.session.refresh(fresh_profile) >> (Pdb) >> >> (Pdb) db.session.refresh(cache_profile) >> *** InvalidRequestError: Instance '<Profile at 0x1075e2b90>' is not >> persistent within this Session >> >> So the status of my cached instance is something other than persistent (is >> there a method to check this?). My theory is that relationship query won't >> fire because it believes it isn't yet saved to the db. >> >> http://docs.sqlalchemy.org/en/latest/orm/session.html#quickie-intro-to-object-states > > yes, inspect() will get you all that > > inspect(my_object).persistent > > http://docs.sqlalchemy.org/en/rel_0_9/orm/internals.html#sqlalchemy.orm.state.InstanceState.persistent > > > > >> >> On Tuesday, January 14, 2014 5:26:19 PM UTC-5, Michael Bayer wrote: >> >> On Jan 14, 2014, at 4:36 PM, [email protected] wrote: >> >> > Help! >> > >> > I'm employing a cache strategy which saves Model instances to an in-memory >> > store. When I retrieve these instances from the cache, I add them to my >> > session. All the data is there, but when I try to use a relationship >> > property it returns None. >> >> “use”, like, my_instance.some_other_object returns None? What kind of SQL >> output do you see when you hit that attribute? How is “my_instance” being >> created in the first place? >> >> >> > >> > A test with two objects: cache_obj and fresh_obj, the only difference I >> > see is that one has a unicode string for it's foreign key and the other >> > does not (which is also strange). >> > >> > (Pdb) fresh_obj_map.attrs['profile'].target == >> > cache_obj_map.attrs['profile'] >> > True >> > >> > (Pdb) cache_obj.profile_id >> > '2cedffc2-7d5c-11e3-8cb0-c82a1412a8b6' >> > >> > (Pdb) fresh_obj.profile_id >> > u'2cedffc2-7d5c-11e3-8cb0-c82a1412a8b6' >> > >> > (Pdb) cache_obj.profile >> > >> > (Pdb) fresh_obj.profile >> > <alphaworks.models.profile.Profile object at 0x10215e910> >> >> if profile_id is a string column all the way then the u’’ ‘’ difference >> shouldn’t be much of an issue. >> >> >> -- >> 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 [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/sqlalchemy. >> For more options, visit https://groups.google.com/groups/opt_out. > > > -- > 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 [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/groups/opt_out.
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