Ah. To answer my own question, what I was actually after was an adjacency list, of which there are examples to be found here, which I missed:
http://www.sqlalchemy.org/docs/05/mappers.html#adjacency-list-relationships I believe this will do what I was after. Sorry for the noise, and thanks anyway. - Peter On 5 October 2010 14:39, Peter Waller <peter.wal...@cern.ch> wrote: > Hi All, > > I have also created a post for this question on StackOverflow: > > http://stackoverflow.com/questions/3863508/joinedload-eager-loading-whole-sub-graphs-in-sqlalchemy > > Let's say I have a Task object which can be dependent on other Tasks. Is > there a way to sensibly eager/joinedload all of a given set of task's > subtasks? > > Example code: > > class Task(DeclarativeBase): > __tablename__ = 'task' > > task_id = Column(Integer, primary_key=True) > name = Column(String, unique=True) > > def add_dependencies(self, *tasks): > for task in tasks: > TaskDependency(dependent=self, dependency=task) > return self > > @property > def dependencies(self): > return [x.dependency for x in self.dependency_edges] > > @dependencies.setter > def dependencies(self, what): > "Note: adds dependencies, doesn't remove them" > self.add_dependencies(*what) > > @property > def dependents(self): > return [x.dependent for x in self.dependent_edges] > > class TaskDependency(DeclarativeBase): > __tablename__ = 'task_dependency' > > dependent_id = Column(Integer, ForeignKey(Task.task_id), > primary_key=True) > dependency_id = Column(Integer, ForeignKey(Task.task_id), > primary_key=True) > > dependent = relationship(Task, primaryjoin=dependent_id == > Task.task_id, > backref='dependent_edges') > > dependency = relationship(Task, primaryjoin=dependency_id == > Task.task_id, > backref='dependency_edges') > > def example_task_maker(): > make_cheese = Task( > name="MAKE_CHEESE", > dependencies=[ > Task(name="MILK_COWS", > dependencies=[ > Task(name="BUY_COWS") > ]), > ] > ) > > > def load_task() > # How to eagerly load the whole task tree here? > DBSession.query(Task).filter(name="MAKE_CHEESE").all() > > Thanks in advance, > > - Peter > -- 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.
