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I have this structure:
class User(DeclarativeBase):
...
teamMemberships = orm.relationship("TeamXREF",backref="user",lazy = "dynamic")
class TeamXREF(DeclarativeBase):
...
class Team(DeclarativeBase):
...
name=db.Column(String)
teamMembers = orm.relationship("TeamXREF",backref="team",lazy = "dynamic")
However, I can't manage to write in 1 query (I always end up with loops and multiple queries) that eager loads all these info at once:
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joined loading - available via lazy='joined' or the joinedload() option, this form of loading applies a JOIN to the given SELECT statement so that related rows are loaded in the same result set.
The relationship function is a part of Relationship API of SQLAlchemy ORM package. It provides a relationship between two mapped classes. This corresponds to a parent-child or associative table relationship.
In Flask-SQLAlchemy, the backref parameter in relationship method allows you to declare a new property under a specified class as seen in the example in their docs: class Person(db.Model): id = db.Column(db.Integer, primary_key=True) name = db.Column(db.String(50)) addresses = db.relationship('Address', backref='person ...
The comments class attribute defines a One-to-Many relationship between the Post model and the Comment model. You use the db. relationship() method, passing it the name of the comments model ( Comment in this case). You use the backref parameter to add a back reference that behaves like a column to the Comment model.
You might try just explicitly loading the items in the query rather than hard coding it into your relationships. Something like this:
from sqlalchemy.orm import joinedload
Session.query(User).options(joinedload('teamMemberships').joinedload('team').joinedload('teamMembers').joinedload('user'))
http://docs.sqlalchemy.org/en/improve_toc/orm/loading_relationships.html#loading-along-paths
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