I'll see if I can nail down the repro; I had to abstract some production
code that I am migrating between versions, and I may have lost some
important detail.
Looking at the SQL it generates before and after moving the "links"
relationship, it appears that it is outer joining against the wrong target,
which explains why the identity map is getting confused. (e.g., it is
joining against the innermost anon_1 subquery in the bad case, and against
the todo_elements_1 reference in the good case, which is why the good case
is forming a nice tree.)
On Tue, Nov 24, 2015 at 3:49 PM, Mike Bayer <mike...@zzzcomputing.com>
wrote:
>
>
> On 11/24/2015 06:14 PM, Christopher Lee wrote:
> >
> > I am having a problem with SQLAlchemy 1.0.9 that cropped up when I
> > upgraded from 0.8.
>
> this is a nicely written test but I get the same recursion overflow
> error when I run it in 0.8, 0.9, and 1.0, even back in 0.8.3. Can you
> provide a script that illustrates success in 0.8 and not in 1.0 ? thanks.
>
>
>
>
>
>
> >
> > I have the following polymorphic relationship defined. For some reason,
> > when I build a tree, and I try to access the children of the middle node
> > of the tree, it is picking up the wrong edge object and going into a
> > recursive loop. (Querying for the children of n2 is picking up the edge
> > e12, instead of the edges e23, e24 and e25.)
> >
> > Looking at the identity map, it looks like the query isn't populating
> > the correct objects.
> >
> > If I move the "links" relationship from the NodesWithEdges class to the
> > base Node class, the query works fine. Also, if I drop join_depth or
> > remove with with_polymorphic mapper arg, it forces multiple queries, and
> > the problem doesn't occur. Is this a bug with the new release, or am I
> > doing something bad?
> >
> >
> > from __future__ import print_function, unicode_literals
> >
> > import sqlalchemy as sa
> > import sqlalchemy.orm
> > import sqlalchemy.ext.associationproxy
> > import sqlalchemy.ext.declarative
> > import sqlalchemy.ext.orderinglist
> >
> > Base = sqlalchemy.ext.declarative.declarative_base()
> >
> >
> > class Node(Base):
> > __tablename__ = 'todo_elements'
> >
> > element_id = sa.Column(sa.Integer, nullable=False, primary_key=True)
> > element_type = sa.Column(sa.String(20), nullable=False)
> >
> > __mapper_args__ = {
> > 'polymorphic_on': element_type,
> > 'with_polymorphic': ('*', None),
> > }
> >
> >
> > class NodeWithEdges(Node):
> > __mapper_args__ = {'polymorphic_identity': 'todo.list'}
> >
> >
> > class LeafNode(Node):
> > __mapper_args__ = {'polymorphic_identity': 'todo.item'}
> >
> > my_flag = sa.Column(sa.Boolean, default=False)
> >
> >
> > class Edge(Base):
> > __tablename__ = 'todo_links'
> > __table_args__ = (
> > sa.PrimaryKeyConstraint('parent_id', 'child_id'),
> > sa.ForeignKeyConstraint(['parent_id'], [Node.element_id]),
> > sa.ForeignKeyConstraint(['child_id'], [Node.element_id]),
> > )
> >
> > parent_id = sa.Column(sa.Integer, nullable=False)
> > child_id = sa.Column(sa.Integer, nullable=False)
> >
> >
> > Edge.child = sa.orm.relationship(
> > Node,
> > uselist=False,
> > primaryjoin=Edge.child_id == Node.element_id,
> > lazy=False,
> > cascade='all',
> > passive_updates=False,
> > join_depth=8,
> > )
> >
> >
> > NodeWithEdges.links = sa.orm.relationship(
> > Edge,
> > primaryjoin=NodeWithEdges.element_id == Edge.parent_id,
> > lazy=False,
> > cascade='all, delete-orphan',
> > single_parent=True,
> > passive_updates=False,
> > join_depth=8,
> > )
> >
> > NodeWithEdges.children = sa.ext.associationproxy.association_proxy(
> > 'links', 'child',
> > creator=lambda child: Edge(child_id=child.element_id))
> >
> >
> >
> > engine = sa.create_engine('sqlite:///:memory:', echo=True)
> > Base.metadata.create_all(engine)
> >
> > Session = sa.orm.sessionmaker(bind=engine)
> > session = Session()
> >
> >
> > #
> > # 1 --> 2 --> 3
> > # --> 4
> > # --> 5
> > #
> >
> > n1 = NodeWithEdges(element_id=1)
> > n2 = NodeWithEdges(element_id=2)
> > n3 = LeafNode(element_id=3)
> > n4 = LeafNode(element_id=4, my_flag=True)
> > n5 = LeafNode(element_id=5)
> >
> > e12 = Edge(parent_id=n1.element_id, child_id=n2.element_id)
> > e23 = Edge(parent_id=n2.element_id, child_id=n3.element_id)
> > e24 = Edge(parent_id=n2.element_id, child_id=n4.element_id)
> > e25 = Edge(parent_id=n2.element_id, child_id=n5.element_id)
> >
> > session.add_all([n1, n2, n3, n4, n5, e12, e23, e24, e25])
> > session.commit()
> > session.expunge_all()
> >
> > new_n1 =
> session.query(NodeWithEdges).filter(NodeWithEdges.element_id==1).first()
> > print(session.identity_map.keys())
> >
> >
> > def traverse(node, f, depth=0):
> > f(node, depth)
> > if hasattr(node, 'children'):
> > for c in node.children:
> > traverse(c, f, depth + 1)
> >
> > def indent_print(node, depth):
> > print(' ' * depth + str(node.element_id))
> > if hasattr(node, 'my_flag'):
> > print(node.my_flag)
> >
> > traverse(new_n1, indent_print)
> >
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