On Oct 18, 2011, at 10:03 AM, fribes wrote:
> Hi all,
>
> Despite some doc and web digging, I didn't find how to tell sqa to behave the
> way I want :
> on deletion on Peripheral, also delete in Actuator.
>
> with the following code, the record in Actuator remains after a deletion, and
> a subsequent creation fails with IntegrityError.
>
> class Peripheral(Base):
> __tablename__ = 'peripheral'
> id = Column(Integer, primary_key=True)
> label = Column(String(20), nullable=False)
>
> __mapper_args__ = {'polymorphic_on': peripheral_type,
> 'polymorphic_identity': 'peripheral'}
>
> class Actuator(Peripheral):
> __tablename__ = 'actuator'
> __mapper_args__ = {'polymorphic_identity': 'actuator'}
> id = Column(None, ForeignKey('peripheral.id'), primary_key=True)
>
> duration = Column(Integer)
>
> Any suggestion ?
usually relationship() with cascade="all, delete-orphan" is used for this use
case, so that SQLAlchemy can maintain knowledge about the link between
Peripheral and Actuator. The other alternative is to use "ON DELETE CASCADE"
on the foreign key; this is part of the schema you'd generate in the database.
Relevant docs:
http://www.sqlalchemy.org/docs/orm/tutorial.html#configuring-delete-delete-orphan-cascade
http://www.sqlalchemy.org/docs/core/schema.html#on-update-and-on-delete
http://www.sqlalchemy.org/docs/orm/collections.html#using-passive-deletes
>
> Regards,
>
>
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