> > I want to direct your attention to some new features in trunk which > I'll also be demonstrating at this years Advanced SQLAlchemy > tutorial. > > these features apply primarily to joined-table inheritance > scenarios, and are in response to the need to specify criterion > against subclasses as well as to join to/from joined-table classes > where a specific subclass is required. > > I've put some new docs at > http://www.sqlalchemy.org/docs/04/mappers.html#advdatamapping_mappe >r_inheritance_joined_querying . > > the two methods are with_polymorphic() and of_type(). > > with_polymorphic() may very well replace the need for select_table > in almost all cases, and it creates the joins for you. It allows > filtering criterion to be against subclasses, *and* allows the > mapper to load the full subclass instance without the need for a > second query against the joined table. > > Assume the usual Person / Engineer(Person) / Manager(Person) > example : > # query for Person objects, but specify criterion against Engineer > > session > .query > (Person > ).with_polymorphic(Engineer).filter(Engineer.engineer_name=='dilber >t') > > # query for Person objects but specify criterion against both > Manager and Engineer > session.query(Person).with_polymorphic([Engineer, > Manager]).filter(or_(Engineer.engineer_name=='dilbert', > Manager.manager_name=='dogbert')) > > # eagerly load all joined-table subclasses > session.query(Person).with_polymorphic('*').filter(...filter on > any table..).all()
let me see if i got it... does this mean that, in the a-b-c-.. mapper hierarchy i do not have anymore to use the selecttable= a.outerjoin(b) (and eventualy .outerjoin(c) etc) on each level, but instead use only one mapper (a) for everything, just having different query.with_poly(x) for each subclass x? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
