Thank you Mike!
That brings me to another question:
Let's say I have created a simple table (well, I have):
class Language(Base):
language_id = Column(Integer, Sequence('language_id_seq',
optional=True), primary_key=True)
language = Column(String(5), unique=True, default='undef')
The problem is (using pdb):
(Pdb) lang = Language(language='test')
(Pdb) lang
<Language(language='test')>
(Pdb) dir(lang)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__',
'__getattribute__', '__hash__', '__init__', '__mapper__',
'__mapper_cls__', '__module__', '__new__', '__reduce__',
'__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__',
'__subclasshook__', '__table__', '__tablename__', '__weakref__',
'_cls_id', '_decl_class_registry', '_has', '_language', '_language_id',
'_sa_class_manager', '_sa_instance_state', 'id_', 'language',
'language_id', 'metadata', 't']
(Pdb) session.add(lang)
(Pdb) session.commit()
(Pdb) lang2 = Language(language='foo')
(Pdb) session.add(lang2)
(Pdb) session.commit()
*** IntegrityError: (IntegrityError) column language is not unique
u'INSERT INTO ht__language (language) VALUES (?)' ('undef',)
(Pdb) session.rollback()
(Pdb) session.query(Language).all()
[<Language(language='test')>]
(Pdb) lang2 = Language()
(Pdb) lang2.language = 'foo'
(Pdb) session.add(lang2)
(Pdb) session.commit()
*** IntegrityError: (IntegrityError) column language is not unique
u'INSERT INTO ht__language (language) VALUES (?)' ('undef',)
(Pdb) session.rollback()
(Pdb) lang2 = Language()
(Pdb) lang2._language = 'foo'
(Pdb) session.add(lang2)
(Pdb) session.commit()
(Pdb) session.query(Language).all()
[<Language()>, <Language(language='test')>]
If I change the Language class to this:
class Language(Base):
language_id = Column(Integer, Sequence('language_id_seq',
optional=True), primary_key=True)
language = Column('language', String(5), unique=True, default='undef')
The same happens. Curiously:
(Pdb) session.query(Language).all()
[<Language()>, <Language(language='test')>]
(Pdb) map(lambda a: a._language, session.query(Language).all())
[u'foo', u'undef']
Is there a problem using this mapper configuration with declarative bases?
Cheers,
Richard.
On 06/07/2013 11:46 AM, Michael Bayer wrote:
On Jun 7, 2013, at 9:31 AM, Richard Gerd Kuesters
<[email protected] <mailto:[email protected]>> wrote:
Hi all!
I'm refactoring a database schema but I need it to mantain reverse
compatibility with older versions of our software - using views.
But, to avoid confusion to other developers, new tables have two
underscores as a prefix, like:
class Base(object):
@declared_attr
def __tablename__(cls):
return "__%s" % to_python_case(cls.__name__)
Now I want to add column prefixes too. I know I can append to this
Base object:
__mapper_args__ = dict(
column_prefix='_'
)
But, when I inherit this new base on classes that I need to use
__mapper_args__, column names probably won't have prefixes. Any
ideas, perhaps an event listener to prepend the underscore into *all*
column names?
one idea is you can intercept how mapper() is called by declarative by
overriding __mapper_cls__, like:
@classmethod
def __mapper_cls__(cls, *args, **kw):
kw['column_prefix'] = '_'
return mapper(*args, **kw)
Cheers,
Richard.
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