Conor wrote: > Kent wrote: > >> I agree I shouldn't care, so maybe there is another way to attack my >> problem. The reason I care is because I've extended the python object >> with some auxiliary information that I need. After the refresh() in >> this case, I still need access to that data that is tied to the >> object, but not present in the database (it is transient data). If >> sqla creates a new instance, I loose that data. >> >> Is there a better mechanism for doing that? >> >> >> > > You need to either manually keep strong references to each object that > has the auxiliary information or disable the weak identity map. See > http://www.sqlalchemy.org/docs/05/session.html#frequently-asked-questions > or > http://www.sqlalchemy.org/docs/05/session.html#frequently-asked-questions > for more information. >
That second link should be http://www.sqlalchemy.org/docs/05/session.html#session-attributes. Oops. >> On Mar 4, 3:38 pm, "Michael Bayer" <mike...@zzzcomputing.com> wrote: >> >> >>> refresh doesn't remove any objects from the session so its a matter of >>> what is present in the session, not marked as dirty, and strongly >>> referenced on the outside. if you're using refresh you shouldn't care >>> about how it gets data back into the collection. >>> >>> Kent wrote: >>> >>> >>>> What's strange is that I can't recreate the problem on more simple >>>> stage. Every time I refresh() on the parent object, the list objects >>>> remain the same. In other words, *sometimes* it behaves as I hope it >>>> to (by apparently refreshing the list's objects) and *sometimes* if >>>> throws them out and creates new ones. The mystery to me is what >>>> determines when it will create new instances vs. refreshing the >>>> existing ones? >>>> >>>> On Mar 4, 3:24 pm, "Michael Bayer" <mike...@zzzcomputing.com> wrote: >>>> >>>> >>>>> Kent wrote: >>>>> >>>>> >>>>>> If I use session.refresh(obj) to re-load an obj that has a one-to-many >>>>>> relational property, the objects in the list are *replaced* instead of >>>>>> *refreshed* if they already exist. >>>>>> >>>>>> Suppose department has a list of employees: >>>>>> >>>>>> suppose dept.employees = [ emp1, emp2 ] >>>>>> >>>>>> session.refresh(dept) >>>>>> >>>>>> the dept."employees" list's elements are replaced with new objects >>>>>> instead of reusing those that existed and refreshing them. >>>>>> >>>>>> Is it possible to have those same objects re-used and simply refreshed >>>>>> instead of replaced? >>>>>> >>>>>> >>>>> you can only turn off "refresh-expire" cascade, which will prohibit the >>>>> operation from traveling into the child objects. the collection is >>>>> still >>>>> refreshed for obvious reasons, its one of the attributes on your mapped >>>>> object. >>>>> >>>>> To achieve your specified behavior, use session.refresh() given as its >>>>> second argument the set of attribute names which are safe to be reloaded >>>>> completely (in this case the scalars). Then for each uselist >>>>> attribute, >>>>> iterate the collection of each and call the desired version of >>>>> session.refresh() for those. >>>>> >>>>> This is an easy refresh() function to create in a generalized way by >>>>> inspecting the class-level attributes of the incoming object. >>>>> > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
