Oh, that worked very well, thank you very much...
E.Ozgur Yilmaz
Lead Technical Director
eoyilmaz.blogspot.com
On Wed, Sep 7, 2011 at 8:04 PM, Michael Bayer <mike...@zzzcomputing.com>wrote:
>
> On Sep 7, 2011, at 12:36 PM, Erkan Özgür Yılmaz wrote:
>
> 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).
>
>
> According to the error message, TaskableEntity has a foreign key to
> Projects and Projects has a foreign key to TaskableEntity, thus creating a
> cycle. TaskableEntity would appear to have this Project foreign key via the
> ProjectMixin class. So I'd add a use_alter=True to one of those
> ForeignKey objects.
>
>
>
>
>
>
> 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
>
>
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