I've taken another look at trying to eager load the address.parent. Is it possible to do that?
I've tried a couple of ways, pasted a below. My full code is at: https://gist.github.com/vfr292/a5939418285e4c8bd03b eager_addresses = session.query(Address).options(joinedload(Address.parent)) #error sqlalchemy.exc.ArgumentError: mapper option expects string key or list of attributes eager_addresses = session.query(Address).options(joinedload (Address.association).joinedload(Customer.assoc_cls.parent), joinedload (Address.association).joinedload(Supplier.assoc_cls.parent)).all() #not joining to Customer or Supplier eager_addresses = session.query(Address).outerjoin(Address.association). outerjoin (Customer.assoc_cls.parent).options(contains_eager(Address.parent)). outerjoin (Supplier.assoc_cls.parent).options(contains_eager(Address.parent).all()) #error sqlalchemy.exc.ArgumentError: mapper option expects string key or list of attributes Any advice on how I can eager load address.parent would be much appreciated :) Sincere thanks, ~Victor On Sunday, October 26, 2014 3:06:13 AM UTC-7, Michael Bayer wrote: > > > On Oct 26, 2014, at 12:07 AM, Victor Reichert <vfr...@gmail.com > <javascript:>> wrote: > > Hi, > > I am following the "Generic Association with Discriminator on Association" > example at: > > > http://docs.sqlalchemy.org/en/latest/_modules/examples/generic_associations/discriminator_on_association.html > > However, I would like to eager load the customer.addresses in a query like > > eager_sales_persons = session.query(SalesPerson).options(joinedload > (SalesPerson.customers).joinedload(Customer.addresses)) > > #with SalesPerson being a class I added with a relationship to customers. > > However, the above statement raises: 'AssociationProxy' object has no > attribute 'property' > > I tried eager_sales_persons = > session.query(SalesPerson).options(joinedload(SalesPerson.customers).joinedload(Customer.address_association).joinedload(AddressAssociation.addresses)).all() > > however, it would emit SQL for customer.addresses. > > I have made a pastie with my code at: http://pastie.org/9676017 > > Is there a loader strategy that would work for my situation or a work > around for the AssociationProxy error? > > > the second query is the right one, as currently there isn’t integration > between an association proxy attribute and loader options, meaning, you > have to state the joinedload() in terms of the actual relationship() as you > are doing. > > However I’m not seeing the problem: > > if we load as : > > > session.query(SalesPerson).options(joinedload(SalesPerson.customers).joinedload(Customer.address_association).joinedload(AddressAssociation.addresses)).all() > > which you can also state like this: > > > session.query(SalesPerson).options(joinedload(SalesPerson.customers).joinedload("address_association").joinedload(“addresses")).all() > > setting echo=True on create_engine(), the main query is: > > SELECT salesperson.id AS salesperson_id, salesperson.name AS > salesperson_name, address_association_1.id AS address_association_1_id, > address_association_1.discriminator AS address_association_1_discriminator, > address_1.id AS address_1_id, address_1.association_id AS > address_1_association_id, address_1.street AS address_1_street, > address_1.city AS address_1_city, address_1.zip AS address_1_zip, > customer_1.id AS customer_1_id, customer_1.name AS customer_1_name, > customer_1.sales_person_id AS customer_1_sales_person_id, > customer_1.address_association_id AS customer_1_address_association_id > FROM salesperson LEFT OUTER JOIN customer AS customer_1 ON salesperson.id > = customer_1.sales_person_id LEFT OUTER JOIN address_association AS > address_association_1 ON address_association_1.id = > customer_1.address_association_id LEFT OUTER JOIN address AS address_1 ON > address_association_1.id = address_1.association_id > > > so in the FROM we have: salesperson -> customer -> address_association > -> address > > that’s correct. you’ll note three joinedload() calls, three links (->). > > then as the iteration proceeds, the sample calls upon address.parent. > This emits this query for two entries: > > SELECT customer.id AS customer_id, customer.name AS customer_name, > customer.sales_person_id AS customer_sales_person_id, > customer.address_association_id AS customer_address_association_id > FROM customer > WHERE ? = customer.address_association_id > > not sure if that’s the query you’re referring to. That’s Address.parent, > which is a proxy to CustomerAddressAssociation.parent, which is emitting a > lazy load. As this is the non-FK side of a one-to-one, that’s also > correct. A one-to-one is a special case of a one-to-many, basically, > uselist=False means, fetch a one-to-many collection, but only deal with the > first result. CustomerAddressAssociation.parent is the backref of the > Customer.address_association many-to-one that’s stated in the joinedload(). > > if this were a non-generic mapping where Customer.addresses were a > one-to-many and Address.parent were a many-to-one, you wouldn’t get that > extra load for Address.parent; a pure many-to-one is implicitly retrieved > from the database and cached that way when the one-to-many side is loaded. > but in this case the “generic” mapping has flipped this around so that > Customer->AddressAssoiation is a many-to-one. > > > > > > > > Thank you so much for your help :) > > ~Victor > > -- > 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+...@googlegroups.com <javascript:>. > To post to this group, send email to sqlal...@googlegroups.com > <javascript:>. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. 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