mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-24 01:22:00 -04:00
Mike Bayer
5329fc481e
remarkably, the examples for concrete and single were still using classical mappings. Ensure all three examples use modern declarative patterns, each illustrate the identical set of query operations. Use back_populates, flat=True for joins, etc. ensure flake8 linting, correct links and add a link back from newly reworked inheritance documentation. Change-Id: I8465a9badbb0eda804f457ccac599f051ee3c27c
158 lines
4.0 KiB
Python
158 lines
4.0 KiB
Python
"""Single-table (table-per-hierarchy) inheritance example."""
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from sqlalchemy import 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, declared_attr
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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(
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"Person",
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back_populates='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(ForeignKey('company.id'))
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name = Column(String(50))
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type = Column(String(50))
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company = relationship("Company", back_populates="employees")
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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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engineer_name = Column(String(30))
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primary_language = Column(String(30))
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# illustrate a single-inh "conflicting" column declaration;
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# see http://docs.sqlalchemy.org/en/latest/orm/extensions/
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# declarative/inheritance.html#resolving-column-conflicts
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@declared_attr
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def status(cls):
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return Person.__table__.c.get('status', 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 (
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"Engineer %s, status %s, engineer_name %s, "
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"primary_language %s" %
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(
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self.name, self.status,
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self.engineer_name, self.primary_language)
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)
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class Manager(Person):
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manager_name = Column(String(30))
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@declared_attr
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def status(cls):
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return Person.__table__.c.get('status', 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(
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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(
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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(
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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(
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['pointy haired boss', '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])
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print(
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session.query(eng_manager).
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filter(
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or_(
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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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)
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# illustrate join from Company,
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eng_manager = with_polymorphic(Person, [Engineer, Manager])
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print(
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session.query(Company).
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join(
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Company.employees.of_type(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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).all())
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session.commit()
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