On Sep 27, 2010, at 4:21 PM, Julien Iguchi-Cartigny wrote:
> Thank you Michael. This solves the problem and... shows a new one.
>
> So this is my update CourseSet
>
> class CourseSet(Base,AbstractContainer):
>
> @classproperty
> def __mapper_args__(self):
> args = dict()
> args.update(AbstractContainer.__mapper_args__)
> args.update({'polymorphic_identity':
> 'org.sakaiproject.coursemanagement.impl.CourseSetCmImpl'})
> return args
>
> Because there is several discriminant values, I need to create other ones:
>
> class CanonicalCourse(Base,AbstractContainer):
>
> @classproperty
> def __mapper_args__(self):
> args = dict()
> args.update(AbstractContainer.__mapper_args__)
> args.update({'polymorphic_identity':
> 'org.sakaiproject.coursemanagement.impl.CanonicalCourseCmImpl'})
> return args
>
>
> But this last one will fail, i've the following error message:
>
> sqlalchemy.exc.InvalidRequestError: Table 'CM_MEMBER_CONTAINER_T' is
> already defined for this MetaData instance. Specify
> 'useexisting=True' to redefine options and columns on an existing
> Table object.
>
> I could use useexisting=True but i don't know if it's the right
> solution. Any ideas ?
that has to do with a Table() statement, or alternatively how you are
configuring __table_name__, neither of which are indicated here, so you need to
ensure that distinct table names are used whenever a table name is declared.
>
> Cheers,
>
> Julien.
>
> On Mon, Sep 27, 2010 at 1:02 AM, Michael Bayer <[email protected]>
> wrote:
>>
>> On Sep 26, 2010, at 6:38 PM, Julien Iguchi-Cartigny wrote:
>>
>>> Hi,
>>>
>>> I'm trying to use polymorphic_on with several inheritances:
>>>
>>> engine = create_engine(
>>> 'mysql://xxx:y...@localhost:3306/zzz?charset=utf8&use_unicode=0',
>>> pool_recycle=3600, echo=True)
>>>
>>> Base = declarative_base()
>>>
>>> class AbstractPersistent(object):
>>> version = Column('VERSION', Integer)
>>> last_modified_by = Column('LAST_MODIFIED_BY', String(255))
>>> last_modified_date = Column('LAST_MODIFIED_DATE', Date)
>>> created_by = Column('CREATED_BY', String(255))
>>> created_date = Column('CREATED_DATE', Date)
>>>
>>> class AbstractNamed(AbstractPersistent):
>>> eid = Column('ENTERPRISE_ID', String(255))
>>> title = Column('TITLE', String(255))
>>> description = Column('DESCRIPTION', String(255))
>>>
>>> class AbstractContainer(AbstractNamed):
>>> __tablename__ = 'CM_MEMBER_CONTAINER_T'
>>> id = Column('MEMBER_CONTAINER_ID',Integer,primary_key=True)
>>> discriminator = Column('CLASS_DISCR', String(100))
>>> __mapper_args__ = {'polymorphic_on': discriminator }
>>>
>>> class CourseSet(Base,AbstractContainer):
>>> __mapper_args__ = {'polymorphic_identity':
>>> 'org.sakaiproject.coursemanagement.impl.CourseSetCmImpl'}
>>
>> AbstractContainer is not mapped, its a mixin, so its __mapper_args__ are not
>> used until a subclass of Base is invoked, which starts up a declarative
>> mapping. Your only mapped class then is CourseSet, which has its own
>> __mapper_args__ , that override those of AbstractContainer - they are
>> ignored.
>>
>> To combine __mapper_args__ from a mapped class with those of a mixin, see
>> the example at
>> http://www.sqlalchemy.org/docs/orm/extensions/declarative.html?highlight=declarative#combining-table-mapper-arguments-from-multiple-mixins
>> . It uses __table_args__ but the same concept of creating a full
>> dictionary of arguments applies for __mapper_args__ as well.
>>
>>
>>
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>>
>
>
>
> --
> "Trouble-a-cat limited"
>
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