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I have many Cs in a B and many Bs in an A, and I have backref relationships defined. What I want to do is something like:
a = A.query().options(subqueryload(A.b).subsubqueryload(B.c)
How should this be done?
679
Use contains_eager() to load back references proactively. This prevents a lazy load to refer back to the parent object, which in turn prevents exceptions when you try to do this when the object is detached from its session.
Joined Load This emits a LEFT OUTER JOIN. Lead object as well as the related object or collection is loaded in one step. from sqlalchemy. orm import joinedload c1 = session. query(Customer).
The loading of relationships falls into three categories; lazy loading, eager loading, and no loading. Lazy loading refers to objects are returned from a query without the related objects loaded at first.
The sqlalchemy backref is one of the type keywords and it passed as the separate argument parameters which has to be used in the ORM mapping objects. It mainly includes the event listener on the configuration attributes with both directions of the user datas through explicitly handling the database relationships.
Straight from the documentation of subqueryload:
qry = query(A).options(subqueryload(A.b).subqueryload(B.c))
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