Hello,
I tried to add alias to column in polymorph2.py in examples/polymorph
and it doesn't work.
Here is what I changed in an example (full example is attached):
25c25
< Column('primary_language', String(50)),
---
> Column('primary_language', String(50), key='primaryLanguage'),
72c72
< engineers.c.primary_language,
---
> engineers.c.primaryLanguage,
When run modified example produses following traceback:
Traceback (most recent call last):
File "C:\home\Vasily\sqlalchemy\sqlalchemy\examples\polymorph\polymorph3.py",
line 114, in ?
c = Company.get(1)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\mapper.py", line 245,
in get
return self.query.get(*ident, **kwargs)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\query.py", line 42, in
get
return self._get(key, ident, **kwargs)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\query.py", line 204,
in _get
return self._select_statement(statement, params=params,
populate_existing=reload)[0]
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\query.py", line 212,
in _select_statement
return self.instances(statement.execute(**params), **kwargs)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\query.py", line 167,
in instances
return self.mapper.instances(session=self.session, *args, **kwargs)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\mapper.py", line 388,
in instances
self._instance(session, row, imap, result,
populate_existing=populate_existing)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\mapper.py", line 737,
in _instance
self.populate_instance(session, instance, row, identitykey, imap, isnew)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\mapper.py", line 760,
in populate_instance
prop.execute(session, instance, row, identitykey, imap, isnew)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\properties.py", line
807, in execute
self._instance(session, row, imap, result_list)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\properties.py", line
837, in _instance
return self.mapper._instance(session, row, imap, result_list)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\mapper.py", line 736,
in _instance
if self.extension.populate_instance(self, session, instance, row,
identitykey, imap, isnew) is EXT_PASS:
File "C:\home\Vasily\sqlalchemy\sqlalchemy\examples\polymorph\polymorph3.py",
line 91, in populate_instance
Engineer.mapper.populate_instance(session, instance, row, identitykey,
imap, isnew, frommapper=mapper)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\mapper.py", line 757,
in populate_instance
row = frommapper.translate_row(self, row)
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\mapper.py", line 752,
in translate_row
newrow[c] = newrow[c.key]
File "C:\Python24\Lib\site-packages\sqlalchemy\util.py", line 189, in
__getitem__
return self.decorate[key]
File "C:\Python24\Lib\site-packages\sqlalchemy\mapping\properties.py", line
816, in __getitem__
return self.row[key]
File "C:\Python24\Lib\site-packages\sqlalchemy\engine.py", line 867, in
__getitem__
return self.__parent._get_col(self.__row, key)
File "C:\Python24\Lib\site-packages\sqlalchemy\engine.py", line 811, in
_get_col
rec = self.props[key.lower()]
KeyError: 'primarylanguage'
Can anyone explain, am I doing something wrong? Or is it a bug in
sqlalchemy?
--
Best regards,
Vasily mailto:[EMAIL PROTECTED]from sqlalchemy import *
import sys
# this example illustrates a polymorphic load of two classes, where each class
has a very
# different set of properties
db = create_engine('sqlite://', echo=True, echo_uow=False)
# a table to store companies
companies = Table('companies', db,
Column('company_id', Integer, primary_key=True),
Column('name', String(50))).create()
# we will define an inheritance relationship between the table "people" and
"engineers",
# and a second inheritance relationship between the table "people" and
"managers"
people = Table('people', db,
Column('person_id', Integer, primary_key=True),
Column('company_id', Integer, ForeignKey('companies.company_id')),
Column('name', String(50))).create()
engineers = Table('engineers', db,
Column('person_id', Integer, ForeignKey('people.person_id'),
primary_key=True),
Column('status', String(30)),
Column('engineer_name', String(50)),
Column('primary_language', String(50), key='primaryLanguage'),
).create()
managers = Table('managers', db,
Column('person_id', Integer, ForeignKey('people.person_id'),
primary_key=True),
Column('status', String(30)),
Column('manager_name', String(50))
).create()
# create our classes. The Engineer and Manager classes extend from Person.
class Person(object):
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 __repr__(self):
return "Company %s" % self.name
# assign plain vanilla mappers
assign_mapper(Person, people)
assign_mapper(Engineer, engineers, inherits=Person.mapper)
assign_mapper(Manager, managers, inherits=Person.mapper)
# create a union that represents both types of joins. we have to use
# nulls to pad out the disparate columns.
person_join = select(
[
people,
managers.c.status,
managers.c.manager_name,
null().label('engineer_name'),
null().label('primary_language'),
column("'manager'").label('type')
],
people.c.person_id==managers.c.person_id).union_all(
select(
[
people,
engineers.c.status,
null().label('').label('manager_name'),
engineers.c.engineer_name,
engineers.c.primaryLanguage,
column("'engineer'").label('type')
],
people.c.person_id==engineers.c.person_id)).alias('pjoin')
print [c for c in person_join.c]
# MapperExtension object.
class PersonLoader(MapperExtension):
def create_instance(self, mapper, row, imap, class_):
if row[person_join.c.type] =='engineer':
return Engineer()
elif row[person_join.c.type] =='manager':
return Manager()
else:
return Person()
def populate_instance(self, mapper, session, instance, row, identitykey,
imap, isnew):
if row[person_join.c.type] =='engineer':
Engineer.mapper.populate_instance(session, instance, row,
identitykey, imap, isnew, frommapper=mapper)
return False
elif row[person_join.c.type] =='manager':
Manager.mapper.populate_instance(session, instance, row,
identitykey, imap, isnew, frommapper=mapper)
return False
else:
return sqlalchemy.mapping.EXT_PASS
people_mapper = mapper(Person, person_join, extension=PersonLoader())
assign_mapper(Company, companies, properties={
'employees': relation(people_mapper, lazy=False, private=True)
})
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(Engineer(name='wally', status='CGG',
engineer_name='engineer2', primary_language='python'))
c.employees.append(Manager(name='jsmith', status='ABA',
manager_name='manager2'))
objectstore.commit()
objectstore.clear()
c = Company.get(1)
for e in c.employees:
print e, e._instance_key
print "\n"
dilbert = Engineer.mapper.get_by(name='dilbert')
dilbert.engineer_name = 'hes dibert!'
objectstore.commit()
objectstore.clear()
c = Company.get(1)
for e in c.employees:
print e, e._instance_key
objectstore.delete(c)
objectstore.commit()
managers.drop()
engineers.drop()
people.drop()
companies.drop()
