I have a simple setup where I create two Nodes connected by an Edge, where
the Edge should be eagerly loaded when the parent is loaded. If I query
the Node with a get(), it issues a select to refresh it, but then if I
access its children, it issues a second get(). This behavior did not used
to occur in 0.8.0. If I expunge the session completely, then a get() will
eagerly load the edges as expected. Is that expected? Did the mechanism
by which get() repopulates the identity map change?
class Node(Base):
__tablename__ = "nodes"
node_id = sa.Column(sa.Integer, primary_key=True)
class Edge(Base):
__tablename__ = 'edges'
parent_id = sa.Column(sa.Integer, sa.ForeignKey(Node.node_id),
primary_key=True)
child_id = sa.Column(sa.Integer, sa.ForeignKey(Node.node_id),
primary_key=True)
Node.children = sa.orm.relationship(
Edge,
cascade="all, delete-orphan",
lazy=False,
uselist=True,
primaryjoin=Node.node_id==Edge.parent_id,
order_by=Edge.parent_id)
engine = sa.create_engine('sqlite:///:memory:', echo=True)
Base.metadata.create_all(engine)
Session = sa.orm.sessionmaker(bind=engine)
session = Session()
n1 = Node(node_id=1)
n2 = Node(node_id=2)
e12 = Edge(parent_id=n1.node_id, child_id=n2.node_id)
session.add_all([n1, n2, e12,])
session.commit()
session.expire_all()
node = session.query(Node).get((1,)) # <-- Issues one select against nodes
with no outer join
edges = node.children # <-- Issues one select against edges with no outer
join
Whereas if I expunge:
session.expunge_all()
node = session.query(Node).get((1,)) # <-- Issues an outer join select
against nodes and edges
edges = node.children # <-- No select statement, pulls from identity map
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