Release: 1.2.0b2 pre release | Release Date: July 24, 2017

SQLAlchemy 1.2 Documentation

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Source code for examples.inheritance.concrete

"""Concrete-table (table-per-class) inheritance example."""

from sqlalchemy import Column, Integer, String, \
    ForeignKey, create_engine, inspect, or_
from sqlalchemy.orm import relationship, Session, with_polymorphic
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.declarative import ConcreteBase


Base = declarative_base()


class Company(Base):
    __tablename__ = 'company'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))

    employees = relationship(
        "Person",
        back_populates='company',
        cascade='all, delete-orphan')

    def __repr__(self):
        return "Company %s" % self.name


class Person(ConcreteBase, Base):
    __tablename__ = 'person'
    id = Column(Integer, primary_key=True)
    company_id = Column(ForeignKey('company.id'))
    name = Column(String(50))

    company = relationship("Company", back_populates="employees")

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

    def __repr__(self):
        return "Ordinary person %s" % self.name


class Engineer(Person):
    __tablename__ = 'engineer'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    company_id = Column(ForeignKey('company.id'))
    status = Column(String(30))
    engineer_name = Column(String(30))
    primary_language = Column(String(30))

    company = relationship("Company", back_populates="employees")

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

    def __repr__(self):
        return (
            "Engineer %s, status %s, engineer_name %s, "
            "primary_language %s" %
            (
                self.name, self.status,
                self.engineer_name, self.primary_language)
        )


class Manager(Person):
    __tablename__ = 'manager'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    company_id = Column(ForeignKey('company.id'))
    status = Column(String(30))
    manager_name = Column(String(30))

    company = relationship("Company", back_populates="employees")

    __mapper_args__ = {
        'polymorphic_identity': 'manager',
        'concrete': True
    }

    def __repr__(self):
        return "Manager %s, status %s, manager_name %s" % (
            self.name, self.status, self.manager_name)


engine = create_engine('sqlite://', echo=True)
Base.metadata.create_all(engine)

session = Session(engine)

c = Company(name='company1', employees=[
    Manager(
        name='pointy haired boss',
        status='AAB',
        manager_name='manager1'),
    Engineer(
        name='dilbert',
        status='BBA',
        engineer_name='engineer1',
        primary_language='java'),
    Person(name='joesmith'),
    Engineer(
        name='wally',
        status='CGG',
        engineer_name='engineer2',
        primary_language='python'),
    Manager(
        name='jsmith',
        status='ABA',
        manager_name='manager2')
])
session.add(c)

session.commit()

c = session.query(Company).get(1)
for e in c.employees:
    print(e, inspect(e).key, e.company)
assert set([e.name for e in c.employees]) == set(
    ['pointy haired boss', 'dilbert', 'joesmith', 'wally', 'jsmith'])
print("\n")

dilbert = session.query(Person).filter_by(name='dilbert').one()
dilbert2 = session.query(Engineer).filter_by(name='dilbert').one()
assert dilbert is dilbert2

dilbert.engineer_name = 'hes dilbert!'

session.commit()

c = session.query(Company).get(1)
for e in c.employees:
    print(e)

# query using with_polymorphic.
eng_manager = with_polymorphic(Person, [Engineer, Manager])
print(
    session.query(eng_manager).
    filter(
        or_(
            eng_manager.Engineer.engineer_name == 'engineer1',
            eng_manager.Manager.manager_name == 'manager2'
        )
    ).all()
)

# illustrate join from Company
eng_manager = with_polymorphic(Person, [Engineer, Manager])
print(
    session.query(Company).
    join(
        Company.employees.of_type(eng_manager)
    ).filter(
        or_(eng_manager.Engineer.engineer_name == 'engineer1',
            eng_manager.Manager.manager_name == 'manager2')
    ).all())

session.commit()