mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-10 10:50:37 -04:00
Mike Bayer
cb3913a186
provides the functionality of query.with_polymorphic() in a standalone form. It can be applied to any entity within a query, including as the target of a join in place of the "of_type()" modifier. [ticket:2333] - redo a large portion of the inheritance docs in terms of declarative, new with_polymorphic() function - upgrade examples/inheritance/polymorph, rename to "joined"
136 lines
3.9 KiB
Python
136 lines
3.9 KiB
Python
"""this example illustrates a polymorphic load of two classes"""
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from sqlalchemy import Table, Column, Integer, String, \
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ForeignKey, create_engine, inspect, or_
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from sqlalchemy.orm import relationship, Session, with_polymorphic
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from sqlalchemy.ext.declarative import declarative_base
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Base = declarative_base()
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class Company(Base):
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__tablename__ = 'company'
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id = Column(Integer, primary_key=True)
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name = Column(String(50))
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employees = relationship("Person",
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backref='company',
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cascade='all, delete-orphan')
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def __repr__(self):
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return "Company %s" % self.name
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class Person(Base):
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__tablename__ = 'person'
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id = Column(Integer, primary_key=True)
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company_id = Column(Integer, ForeignKey('company.id'))
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name = Column(String(50))
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type = Column(String(50))
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__mapper_args__ = {
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'polymorphic_identity':'person',
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'polymorphic_on':type
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}
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def __repr__(self):
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return "Ordinary person %s" % self.name
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class Engineer(Person):
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__tablename__ = 'engineer'
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id = Column(Integer, ForeignKey('person.id'), primary_key=True)
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status = Column(String(30))
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engineer_name = Column(String(30))
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primary_language = Column(String(30))
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__mapper_args__ = {
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'polymorphic_identity':'engineer',
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}
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def __repr__(self):
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return "Engineer %s, status %s, engineer_name %s, "\
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"primary_language %s" % \
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(self.name, self.status,
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self.engineer_name, self.primary_language)
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class Manager(Person):
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__tablename__ = 'manager'
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id = Column(Integer, ForeignKey('person.id'), primary_key=True)
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status = Column(String(30))
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manager_name = Column(String(30))
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__mapper_args__ = {
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'polymorphic_identity':'manager',
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}
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def __repr__(self):
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return "Manager %s, status %s, manager_name %s" % \
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(self.name, self.status, self.manager_name)
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engine = create_engine('sqlite://', echo=True)
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Base.metadata.create_all(engine)
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session = Session(engine)
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c = Company(name='company1', employees=[
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Manager(
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name='pointy haired boss',
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status='AAB',
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manager_name='manager1'),
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Engineer(name='dilbert',
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status='BBA',
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engineer_name='engineer1',
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primary_language='java'),
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Person(name='joesmith'),
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Engineer(name='wally',
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status='CGG',
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engineer_name='engineer2',
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primary_language='python'),
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Manager(name='jsmith',
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status='ABA',
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manager_name='manager2')
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])
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session.add(c)
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session.commit()
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c = session.query(Company).get(1)
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for e in c.employees:
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print e, inspect(e).key, e.company
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assert set([e.name for e in c.employees]) == set(['pointy haired boss',
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'dilbert', 'joesmith', 'wally', 'jsmith'])
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print "\n"
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dilbert = session.query(Person).filter_by(name='dilbert').one()
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dilbert2 = session.query(Engineer).filter_by(name='dilbert').one()
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assert dilbert is dilbert2
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dilbert.engineer_name = 'hes dilbert!'
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session.commit()
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c = session.query(Company).get(1)
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for e in c.employees:
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print e
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# query using with_polymorphic.
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eng_manager = with_polymorphic(Person, [Engineer, Manager], aliased=True)
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print session.query(eng_manager).\
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filter(
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or_(eng_manager.Engineer.engineer_name=='engineer1',
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eng_manager.Manager.manager_name=='manager2'
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)
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).all()
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# illustrate join from Company,
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# We use aliased=True
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# to help when the selectable is used as the target of a join.
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eng_manager = with_polymorphic(Person, [Engineer, Manager], aliased=True)
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print session.query(Company).\
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join(
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eng_manager,
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Company.employees
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).filter(
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or_(eng_manager.Engineer.engineer_name=='engineer1',
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eng_manager.Manager.manager_name=='manager2')
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).all()
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session.commit()
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