mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-10 19:00:25 -04:00
Mike Bayer
126 lines
4.1 KiB
Python
126 lines
4.1 KiB
Python
from sqlalchemy import MetaData, Table, Column, Integer, String, \
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ForeignKey, create_engine
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from sqlalchemy.orm import mapper, relationship, sessionmaker
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# this example illustrates a polymorphic load of two classes
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metadata = MetaData()
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# a table to store companies
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companies = Table('companies', metadata,
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Column('company_id', Integer, primary_key=True),
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Column('name', String(50)))
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# we will define an inheritance relationship between the table "people" and
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# "engineers", and a second inheritance relationship between the table
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# "people" and "managers"
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people = Table('people', metadata,
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Column('person_id', Integer, primary_key=True),
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Column('company_id', Integer, ForeignKey('companies.company_id')),
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Column('name', String(50)),
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Column('type', String(30)))
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engineers = Table('engineers', metadata,
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Column('person_id', Integer, ForeignKey('people.person_id'),
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primary_key=True),
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Column('status', String(30)),
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Column('engineer_name', String(50)),
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Column('primary_language', String(50)),
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)
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managers = Table('managers', metadata,
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Column('person_id', Integer, ForeignKey('people.person_id'),
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primary_key=True),
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Column('status', String(30)),
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Column('manager_name', String(50))
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)
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# create our classes. The Engineer and Manager classes extend from Person.
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class Person(object):
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def __init__(self, **kwargs):
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for key, value in kwargs.iteritems():
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setattr(self, key, value)
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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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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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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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class Company(object):
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def __init__(self, **kwargs):
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for key, value in kwargs.iteritems():
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setattr(self, key, value)
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def __repr__(self):
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return "Company %s" % self.name
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person_mapper = mapper(Person, people, polymorphic_on=people.c.type,
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polymorphic_identity='person')
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mapper(Engineer, engineers, inherits=person_mapper,
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polymorphic_identity='engineer')
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mapper(Manager, managers, inherits=person_mapper,
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polymorphic_identity='manager')
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mapper(Company, companies, properties={'employees'
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: relationship(Person, lazy='joined', backref='company',
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cascade='all, delete-orphan')})
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engine = create_engine('sqlite://', echo=True)
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metadata.create_all(engine)
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session = sessionmaker(engine)()
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c = Company(name='company1')
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c.employees.append(Manager(name='pointy haired boss', status='AAB',
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manager_name='manager1'))
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c.employees.append(Engineer(name='dilbert', status='BBA',
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engineer_name='engineer1', primary_language='java'))
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c.employees.append(Person(name='joesmith', status='HHH'))
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c.employees.append(Engineer(name='wally', status='CGG',
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engineer_name='engineer2', primary_language='python'
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))
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c.employees.append(Manager(name='jsmith', status='ABA',
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manager_name='manager2'))
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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, e._sa_instance_state.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 dibert!'
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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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# illustrate querying using direct table access:
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print session.query(Engineer.engineer_name).\
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select_from(engineers).\
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filter(Engineer.primary_language=='python').\
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all()
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session.delete(c)
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session.commit()
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