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On 13.01.2009 15:52 Uhr, Michael Bayer wrote:
>
> On Jan 13, 2009, at 8:19 AM, Andreas Jung wrote:
>
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>> Is it possible to define multiple mappers for one table?
>>
>> Usecase: I have one big table (60 cols) and one big mapper class.
>> For some reporting I don't need only a small number of cols. For
>> performance reasons I would like to load the related rows using a very
>> minimal mapper. However there is no obvious way to configure a
>> non-primary mapper using the declarative layer?
>
> declarative can't create non primary mappers (it would be a
> contradiction), but "non primary mapper" only applies to multiple
> mappers for a class, not for a table. any number of mappers of any
> kind can point to a single table.
>
> to map to any table just set the __table__ argument to the Table. if
> you already have another declarative class, youd say __table__ =
> MyOtherClass.__table__.
>
>
This fails:
This is full-fledged mapper:
class Arbeitsmittel(Base, AsDictMixin):
__tablename__ = 'arbeitsmittel'
__table_args__ = (
{ 'autoload' : True, })
# column redefinitions needed for relation()s below
idfassung = Column(Integer, ForeignKey('fassung.id'))
format = Column(String, ForeignKey('format.format'))
status = Column(Integer, ForeignKey('status.id'))
idsachgebiet = Column(Integer, ForeignKey('sachgebiet.id'))
idzielgruppe = Column(Integer, ForeignKey('zielgruppen.id'))
idgattung = Column(Integer, ForeignKey('gattung.id'))
styleguide_compliant = Column(Integer,
ForeignKey('styleguide_compliant.id'))
The minimal mapper looks like this:
class ArbeitsmittelMinimal(Base, AsDictMixin):
__table__ = Arbeitsmittel.__table__
hidx = Column(String, primary_key=True)
/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/engine/base.py:1265:
SAWarning: Predicate of partial index hierarchies_pid_is_root_true
ignored during reflection
self.dialect.reflecttable(conn, table, include_columns)
2009-01-13 16:03:47 ERROR Zope Couldn't install Toolbox
Traceback (innermost last):
Module OFS.Application, line 806, in install_product
- __traceback_info__: Toolbox
Module Products.Toolbox, line 20, in initialize
Module toolbox.database.setup, line 74, in setup
Module z3c.sqlalchemy.util, line 70, in createSAWrapper
Module z3c.sqlalchemy.base, line 81, in __init__
Module toolbox.database.model, line 791, in getModel
Module toolbox.database.model, line 779, in modelAll
Module sqlalchemy.ext.declarative, line 372, in __init__
Module sqlalchemy.ext.declarative, line 364, in _as_declarative
Module sqlalchemy.orm, line 736, in mapper
Module sqlalchemy.orm.mapper, line 196, in __init__
Module sqlalchemy.orm.mapper, line 481, in _configure_properties
Module sqlalchemy.orm.mapper, line 578, in _compile_property
Module sqlalchemy.schema, line 618, in __str__
Module sqlalchemy.util, line 1358, in __get__
Module sqlalchemy.sql.expression, line 2805, in description
AttributeError: 'NoneType' object has no attribute 'encode'
Traceback (most recent call last):
File "<string>", line 1, in ?
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/Zope2/__init__.py",
line 55, in app
startup()
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/Zope2/__init__.py",
line 51, in startup
_startup()
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/Zope2/App/startup.py",
line 138, in startup
OFS.Application.initialize(application)
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/OFS/Application.py",
line 303, in initialize
initializer.initialize()
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/OFS/Application.py",
line 332, in initialize
self.install_products()
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/OFS/Application.py",
line 612, in install_products
return install_products(app)
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/OFS/Application.py",
line 647, in install_products
raise_exc=raise_on_error,
File
"/local/HRS2/Devel/junga/tb-dev/parts/zope2/lib/python/OFS/Application.py",
line 806, in install_product
initmethod(context)
File
"/local/HRS2/Devel/junga/tb-dev/parts/products-svn/Toolbox/__init__.py",
line 20, in initialize
setup(forZope=True, echo=echo)
File
"/local/HRS2/Devel/junga/tb-dev/parts/modules-svn/toolbox/database/setup.py",
line 74, in setup
name=TOOLBOX_WRAPPER_NAME)
File
"/local/HRS2/Devel/junga/tb-dev/eggs/z3c.sqlalchemy-1.3.9-py2.4.egg/z3c/sqlalchemy/util.py",
line 70, in createSAWrapper
extension_options=extension_options,
File
"/local/HRS2/Devel/junga/tb-dev/eggs/z3c.sqlalchemy-1.3.9-py2.4.egg/z3c/sqlalchemy/base.py",
line 81, in __init__
self._model = model(self.metadata)
File
"/local/HRS2/Devel/junga/tb-dev/parts/modules-svn/toolbox/database/model.py",
line 791, in getModel
modelAll(Base, model)
File
"/local/HRS2/Devel/junga/tb-dev/parts/modules-svn/toolbox/database/model.py",
line 779, in modelAll
class ArbeitsmittelMinimal(Base, AsDictMixin):
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/ext/declarative.py",
line 372, in __init__
_as_declarative(cls, classname, dict_)
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/ext/declarative.py",
line 364, in _as_declarative
cls.__mapper__ = mapper_cls(cls, table, properties=our_stuff,
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/orm/__init__.py",
line 736, in mapper
return Mapper(class_, local_table, *args, **params)
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/orm/mapper.py",
line 196, in __init__
self._configure_properties()
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/orm/mapper.py",
line 481, in _configure_properties
self._compile_property(key, prop, False)
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/orm/mapper.py",
line 578, in _compile_property
raise sa_exc.ArgumentError("Column '%s' is not represented in
mapper's table. "
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/schema.py",
line 618, in __str__
return self.description
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/util.py",
line 1358, in __get__
obj.__dict__[self.__name__] = result = self.fget(obj)
File
"/local/HRS2/Devel/junga/tb-dev/eggs/SQLAlchemy-0.5.0-py2.4.egg/sqlalchemy/sql/expression.py",
line 2805, in description
return self.name.encode('ascii', 'backslashreplace')
AttributeError: 'NoneType' object has no attribute 'encode'
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