CODEWITHSUNDEEP
pythoninheritancesqlalchemy
jupiterjones
jupiterjones

Reputation: 51

Sqlalchemy inheritance - delete child row without deleting the parent row?

class Employee(Base):
    __tablename__ = 'employee'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    type = Column(String(50))

    __mapper_args__ = {
        'polymorphic_identity':'employee',
        'polymorphic_on':type
    }
class Engineer(Employee):
    __tablename__ = 'engineer'
    id = Column(Integer, ForeignKey('employee.id'), primary_key=True)
    engineer_name = Column(String(30))

    __mapper_args__ = {
        'polymorphic_identity':'engineer',
    }

e = Engineer()
session.add(e)
session.commit()

Creating an object of Engineer will add a row in both employee and engineer table.

session.delete(e)
session.commit()

Now when I delete the engineer object I want to only remove the row in engineer table and not in the employee table. How do I achieve this? Right now the rows in both table gets removed.

Any help/suggestions would be highly appreciated.

Upvotes: 5

Views: 3387

Answers (1)

Haleemur Ali
Haleemur Ali

Reputation: 28253

If you delete the engineer object using the ORM (by calling session.delete(obj)), then it will delete records from both tables.

However, what you want may be accomplished by 

session.query(Engineer).filter(Engineer.id==e.id).delete()
session.commit()

Upvotes: 6

Related Questions