1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
|
from sqlalchemy import MetaData, Table, Column, Integer, String, ForeignKey
from sqlalchemy.orm import mapper, relationship, create_session
metadata = MetaData('sqlite://')
metadata.bind.echo = 'debug'
# a table to store companies
companies = Table('companies', metadata,
Column('company_id', Integer, primary_key=True),
Column('name', String(50)))
employees_table = Table('employees', metadata,
Column('employee_id', Integer, primary_key=True),
Column('company_id', Integer, ForeignKey('companies.company_id')),
Column('name', String(50)),
Column('type', String(20)),
Column('status', String(20)),
Column('engineer_name', String(50)),
Column('primary_language', String(50)),
Column('manager_name', String(50))
)
metadata.create_all()
class Person(object):
def __init__(self, **kwargs):
for key, value in kwargs.iteritems():
setattr(self, key, value)
def __repr__(self):
return "Ordinary person %s" % self.name
class Engineer(Person):
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):
def __repr__(self):
return "Manager %s, status %s, manager_name %s" % (self.name, self.status, self.manager_name)
class Company(object):
def __init__(self, **kwargs):
for key, value in kwargs.iteritems():
setattr(self, key, value)
def __repr__(self):
return "Company %s" % self.name
person_mapper = mapper(Person, employees_table, polymorphic_on=employees_table.c.type, polymorphic_identity='person')
manager_mapper = mapper(Manager, inherits=person_mapper, polymorphic_identity='manager')
engineer_mapper = mapper(Engineer, inherits=person_mapper, polymorphic_identity='engineer')
mapper(Company, companies, properties={
'employees': relationship(Person, lazy=True, backref='company')
})
session = create_session()
c = Company(name='company1')
c.employees.append(Manager(name='pointy haired boss', status='AAB', manager_name='manager1'))
c.employees.append(Engineer(name='dilbert', status='BBA', engineer_name='engineer1', primary_language='java'))
c.employees.append(Person(name='joesmith', status='HHH'))
c.employees.append(Engineer(name='wally', status='CGG', engineer_name='engineer2', primary_language='python'))
c.employees.append(Manager(name='jsmith', status='ABA', manager_name='manager2'))
session.add(c)
session.flush()
session.expunge_all()
c = session.query(Company).get(1)
for e in c.employees:
print e, e.company
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 dibert!'
session.flush()
session.expunge_all()
c = session.query(Company).get(1)
for e in c.employees:
print e
session.delete(c)
session.flush()
metadata.drop_all()
|
