Hi all,
I am using declarative to model an existing object hierarchy where
there is an
abstract part that i model as an hierarchy of mixins and a concrete
part where
i use joined-table inheritance.
I have a problem when there is attributes with the same name, one
overriding
the other, in the abstract mixin hierarchy. Maybe I am doing something
wrong
so suggestions for how to implement this is most welcome.
Sample code:
import unittest
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, String, Integer, Boolean
Base = declarative_base()
class AbstractA(object):
AttrA = Column(String(50))
def __init__(self, AttrA="AttrA"):
self.AttrA = AttrA
class AbstractB(AbstractA):
AttrA = Column(String(50), primary_key=True)
def __init__(self, AttrA, **kwargs):
AbstractA.__init__(self, **kwargs)
self.AttrA = AttrA
class Concrete(Base, AbstractB):
__tablename__ = 'Concrete'
AttrB = Column(Boolean)
def __init__(self, AttrB, **kwargs):
AbstractB.__init__(self, **kwargs)
self.AttrB = AttrB
class TestAttributeOverriding(unittest.TestCase):
def testAttributeOverriding(self):
concrete = Concrete(AttrB = False, AttrA="0")
self.session.add(concrete)
self.session.commit()
assert len(self.session.query(Concrete).all()) == 1
def setUp(self):
self.engine = create_engine('sqlite:///:memory:', echo = True)
Session = sessionmaker(bind = self.engine)
self.session = Session()
self.metadata = Base.metadata
self.metadata.create_all(self.engine)
def tearDown(self):
self.metadata.drop_all(self.engine)
self.session.close()
This would fail with "could not assemble any primary key columns for
mapped
table" unless i apply the small patch below, which makes it work as i
would
expect (although i don't know if this is how it is intended to be):
--- /usr/lib/python2.6/site-packages/sqlalchemy/ext/
declarative.py
2010-09-07 19:05:34.000000000 +0200
+++ lib/python2.6/site-packages/SQLAlchemy-0.6.4-
py2.6.egg/sqlalchemy/ext/declarative.py 2010-10-21
19:58:15.863671633
+0200
@@ -936,11 +936,13 @@
'__table__' in dict_ and
name in dict_['__table__'].c
):
- potential_columns[name] = \
- column_copies[obj] = \
- obj.copy()
- column_copies[obj]._creation_order = \
- obj._creation_order
+ if name not in potential_columns:
+ potential_columns[name] = \
+ column_copies[obj] = \
+ obj.copy()
+ column_copies[obj]._creation_order =
\
+ obj._creation_order
+
elif isinstance(obj, MapperProperty):
raise exceptions.InvalidRequestError(
"Mapper properties (i.e. deferred,"
---
Oystein
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