ok, many thx
fma
Le 26 août 2010 à 17:03, Michael Bayer a écrit :
>
> On Aug 26, 2010, at 8:49 AM, Martin-Leon Francois wrote:
>
>> hi,
>>
>> The problem seems to be a little bit more general, I have a unique class
>> (doing nothing) mapped to a unique table.
>> After opening a session, I create an instance, add it to the session, flush,
>> commit.
>> Everything is ok. --> a row in the table, instance in the identity_map of
>> the session
>>
>> Always in the same session, I delete the instance from the session., flush,
>> commit.
>> Everything is ok. --> no row in the table, no instance in the identity_map
>> of the session
>>
>> Always the same session, I add again the python instance to the session,
>> flush, commit.
>> ??? --> no row in the table, instance in the identity_map of the session
>>
>> Could you have a look to the code below and help me figure out what I doing
>> wrong?
>> fma
>>
>> #If I uncomment the following line (workaround) instance is written down to
>> #the database as I would expect
>> #o1._sa_instance_state = o1._sa_class_manager._create_instance_state(o1)
>>
>> s.add(o1)
>> s.add_all([o1])
>> s.flush()
>> s.commit()
>> print list(s.query(One)), s.identity_map
>> s.close()
>
> OK this is a little strange. o1 has been deleted. You've found one
> particular operation that doesn't immediately raise (add()), but anything
> else you did with o1 would, for example:
>
> print o1.name
>
> you will get this (since o1 is expired and will refresh, then fail):
>
> sqlalchemy.orm.exc.ObjectDeletedError: Instance '<One at 0x1288c70>'
> has been deleted.
>
> as you've already figured out, o1 has state on it that tells SQLAlchemy that
> this object is already persistent - no INSERT will be executed again for the
> object. The strange part here is that the object is beyond persistent and
> is in the deleted state, and we don't have an in-memory flag that would
> signal this, though perhaps that is called for here, I've never seen anyone
> trying to perform such an operation before.
>
> Anyway to convert from persistent back to transient, use make_transient:
>
> from sqlalchemy.orm import make_transient
> make_transient(o1)
>
> then the "key" is removed and the object is as though you just created it.
>
> I want to check if there's some foolproof way we can block on add().
>
> Also, the add()/add_all() calls are redundant as is the flush() right before
> the commit().
>
>
>>
>> Le 26 août 2010 à 08:42, fma a écrit :
>>
>>> Any suggestion helping solving this?
>>>
>>> On 25 août, 13:02, Martin-Leon Francois <francois....@gmail.com>
>>> wrote:
>>>> Hi,
>>>>
>>>> I am trying in the same session to detach an instance from a collection (
>>>> one to many)
>>>> flush and commit everything (all is ok) and then attach the removed
>>>> instance again. unsuccessfully.
>>>>
>>>> in below code, last "assert" fails.
>>>> I don't understand why I am not able to append m2 to o1.to_many collection
>>>> once removed.
>>>>
>>>> Any idea? ( I use sa 0.5.6)
>>>>
>>>> thanx, Francois
>>>>
>>>> meta = MetaData()
>>>> tb_one = Table("one", meta,
>>>> Column('name',String(50)),
>>>> Column('id',Integer, primary_key=True))
>>>>
>>>> tb_many = Table("many", meta,
>>>> Column('name',String(50)),
>>>> Column('id',Integer, primary_key=True),
>>>> Column('one_id', Integer,
>>>> ForeignKey(tb_one.c.id,ondelete='CASCADE'), nullable=False),)
>>>>
>>>> class One(object):
>>>> def __init__(self, name):
>>>> self.name = name
>>>>
>>>> class Many(object):
>>>> def __init__(self, name):
>>>> self.name = name
>>>>
>>>> mapper_one = mapper(One,tb_one)
>>>> mapper_many = mapper(Many, tb_many,
>>>> properties = dict(
>>>> to_one = relation(One,uselist=False,
>>>> backref=backref('to_many', cascade="save-update, merge, delete,
>>>> delete-orphan"),)))
>>>>
>>>> engine = create_engine(....)
>>>> Session = orm.sessionmaker(autoflush=True, autocommit=False, bind=engine)
>>>>
>>>> meta.bind = engine
>>>> meta.drop_all(checkfirst=True)
>>>> meta.create_all(checkfirst=True)
>>>>
>>>> s = Session()
>>>> m1 = Many("M1")
>>>> m2 = Many("M2")
>>>> o1 = One("One")
>>>> o1.to_many.append(m1)
>>>> o1.to_many.append(m2)
>>>>
>>>> s.add_all([m1,m2,o1])
>>>> s.flush()
>>>> s.commit()
>>>> assert(len(o1.to_many) == 2)
>>>>
>>>> o1.to_many.remove(m2)
>>>> assert(len(o1.to_many) == 1)
>>>> s.flush()
>>>> s.commit()
>>>> assert(len(o1.to_many) == 1)
>>>>
>>>> o1.to_many.append(m2)
>>>> assert(len(o1.to_many) == 2)
>>>> s.flush()
>>>> s.commit()
>>>> assert(len(o1.to_many) == 2) #this assert fails why?
>>>>
>>>> s.close()
>>>
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>>
>>
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>
>
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