The following gives CircularDependencyError
where I think there isn't, but you know I don't know that much the internals
of SQLAlchemy and maybe (and it is a strong possibility) I'm wrong. I've
ripped of the classes causing the error (copy/paste will re-produce the
error).
from sqlalchemy import orm, create_engine
from sqlalchemy.orm import relationship, synonym, validates
from sqlalchemy import (Table, Column, ForeignKey, Boolean, Integer, String)
from sqlalchemy.ext.declarative import (declarative_base, synonym_for,
declared_attr)
Base = declarative_base()
########################################################################
class SimpleEntity(Base):
__tablename__ = "SimpleEntities"
id = Column("id", Integer, primary_key=True)
entity_type = Column("db_entity_type", String(128), nullable=False)
__mapper_args__ = {
"polymorphic_on": entity_type,
"polymorphic_identity": "SimpleEntity",
}
########################################################################
class Entity(SimpleEntity):
__tablename__ = "Entities"
__mapper_args__ = {"polymorphic_identity": "Entity"}
entity_id = Column("id", Integer, ForeignKey("SimpleEntities.id"),
primary_key=True)
########################################################################
class Task(Entity):
__tablename__ = "Tasks"
__mapper_args__ = {"polymorphic_identity": "Task"}
task_id = Column("id", Integer, ForeignKey("Entities.id"),
primary_key=True)
task_of_id = Column(Integer, ForeignKey("TaskableEntities.id"))
########################################################################
class ProjectMixin(object):
#----------------------------------------------------------------------
@declared_attr
def project_id(cls):
return Column(
"project_id",
Integer,
ForeignKey("Projects.id"),
)
#----------------------------------------------------------------------
@declared_attr
def project(cls):
return relationship(
"Project",
primaryjoin=\
cls.__name__ + ".project_id==Project.project_id_local",
post_update=True, # for project itself
uselist=False
)
#----------------------------------------------------------------------
def __init__(self,
project=None,
**kwargs):
self.project = project
########################################################################
class TaskableEntity(Entity, ProjectMixin):
__tablename__ = "TaskableEntities"
__mapper_args__ = {"polymorphic_identity": "TaskableEntity"}
taskableEntity_id = Column("id", Integer, ForeignKey("Entities.id"),
primary_key=True)
tasks = relationship(
"Task",
primaryjoin=taskableEntity_id==Task.task_of_id,
backref="task_of",
post_update=True,
)
########################################################################
class Project(TaskableEntity):
__tablename__ = "Projects"
project_id_local = Column("id", Integer,
ForeignKey("TaskableEntities.id"),
primary_key=True)
__mapper_args__ = {"polymorphic_identity": "Project",
"inherit_condition":
project_id_local==TaskableEntity.taskableEntity_id}
engine = create_engine("sqlite:///:memory:")
Base.metadata.create_all(engine)
Session = sqlalchemy.orm.sessionmaker(bind=dengine)
session = Session()
The Error message:
sqlalchemy.exc.CircularDependencyError: Circular dependency detected:
cycles:
set([
Table('TaskableEntities', MetaData(None),
Column('id', Integer(), ForeignKey('Entities.id'),
table=<TaskableEntities>, primary_key=True, nullable=False),
Column('project_id', Integer(), ForeignKey('Projects.id'),
table=<TaskableEntities>), schema=None),
Table('Projects', MetaData(None),
Column('id', Integer(), ForeignKey('TaskableEntities.id'),
table=<Projects>, primary_key=True, nullable=False), schema=None)]
) all edges:
set(
[
(Table('TaskableEntities', MetaData(None),
Column('id', Integer(), ForeignKey('Entities.id'),
table=<TaskableEntities>, primary_key=True, nullable=False),
Column('project_id', Integer(), ForeignKey('Projects.id'),
table=<TaskableEntities>), schema=None),
Table('Projects', MetaData(None),
Column('id', Integer(), ForeignKey('TaskableEntities.id'),
table=<Projects>, primary_key=True, nullable=False), schema=None)),
(Table('SimpleEntities', MetaData(None),
Column('id', Integer(), table=<SimpleEntities>,
primary_key=True, nullable=False),
Column('db_entity_type', String(length=128),
table=<SimpleEntities>, nullable=False), schema=None),
Table('Entities', MetaData(None),
Column('id', Integer(), ForeignKey('SimpleEntities.id'),
table=<Entities>, primary_key=True, nullable=False), schema=None)),
(Table('TaskableEntities', MetaData(None),
Column('id', Integer(), ForeignKey('Entities.id'),
table=<TaskableEntities>, primary_key=True, nullable=False),
Column('project_id', Integer(), ForeignKey('Projects.id'),
table=<TaskableEntities>), schema=None),
Table('Tasks', MetaData(None),
Column('id', Integer(), ForeignKey('Entities.id'),
table=<Tasks>, primary_key=True, nullable=False),
Column('task_of_id', Integer(),
ForeignKey('TaskableEntities.id'), table=<Tasks>), schema=None)),
(Table('Entities', MetaData(None),
Column('id', Integer(), ForeignKey('SimpleEntities.id'),
table=<Entities>, primary_key=True, nullable=False), schema=None),
Table('Tasks', MetaData(None),
Column('id', Integer(), ForeignKey('Entities.id'),
table=<Tasks>, primary_key=True, nullable=False),
Column('task_of_id', Integer(),
ForeignKey('TaskableEntities.id'), table=<Tasks>), schema=None)),
(Table('Entities', MetaData(None),
Column('id', Integer(), ForeignKey('SimpleEntities.id'),
table=<Entities>, primary_key=True, nullable=False), schema=None),
Table('TaskableEntities', MetaData(None),
Column('id', Integer(), ForeignKey('Entities.id'),
table=<TaskableEntities>, primary_key=True, nullable=False),
Column('project_id', Integer(), ForeignKey('Projects.id'),
table=<TaskableEntities>), schema=None)),
(Table('Projects', MetaData(None),
Column('id', Integer(), ForeignKey('TaskableEntities.id'),
table=<Projects>, primary_key=True, nullable=False), schema=None),
Table('TaskableEntities', MetaData(None),
Column('id', Integer(), ForeignKey('Entities.id'),
table=<TaskableEntities>, primary_key=True, nullable=False),
Column('project_id', Integer(), ForeignKey('Projects.id'),
table=<TaskableEntities>), schema=None))
]
)
E.Ozgur Yilmaz
Lead Technical Director
eoyilmaz.blogspot.com
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To post to this group, send email to sqlalchemy@googlegroups.com.
To unsubscribe from this group, send email to
sqlalchemy+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/sqlalchemy?hl=en.
