Michael,
Thanks always for your time! amazing those details answers.
I looked at the code and see they did something like this:
beforeSerials = self._serials[:]
Then a few lines later followed by:
self._serials.append(MetaSerial(value=u'))
Then followed by
afterSerials = self._serials
Then followed by:
Session.flush()
So It is similar to what you described,
Thanks again.
marc
On Saturday, October 12, 2013 6:41:19 PM UTC-4, Michael Bayer wrote:
>
>
> On Oct 12, 2013, at 11:54 AM, Marc Van Olmen
> <marcva...@gmail.com<javascript:>>
> wrote:
>
> > hi,
> >
> > Just wanted to quickly report this issue, didn't had time to write unit
> test for corning the case:
> > Was upgrading an 0.4.8 legacy project to 0.8.2
> >
> > Got an SAWarning: This collection has been invalidated in the following
> case:
> >
> > Original 0.4.8 code:
> >
> > self._serials.append(MetaSerial(value=u'))
> >
> > And failed to add it to the collection.
> >
> > The fix needed to get rid of the above warning:
> >
> > a_serial = MetaSerial(value=u'')
> > self._serials.append(a_serial)
>
>
> there's nothing in the mapping or sample code illustrated here that by
> itself would emit this warning. The warning itself is not a bug, but
> instead refers to a bug in the calling code, where it is erroneously
> appending to a collection that is no longer valid, due to expiration.
> Expiration on session commit was introduced as a default behavior in 0.5
> and the collection mechanics also changed significantly from 0.5 on
> forward.
>
> The code example you have suggests a premature garbage collection of some
> resource due to the way MetaSerial is not assigned to a variable in one
> case vs. the other, but that's not really possible with a straight append
> to a mapped collection as above, and that also doesn't have any direct path
> to causing this very specific collection-oriented warning from being
> emitted. So either this code isn't the primary cause of the issue, or
> there's something more complex going on in the actual classes and/or
> mappings that produces this.
>
> To produce the warning, you have to do something equivalent to the sample
> code below:
>
> from sqlalchemy import *
> from sqlalchemy.orm import *
> from sqlalchemy.ext.declarative import declarative_base
>
> Base = declarative_base()
>
> class A(Base):
> __tablename__ = 'a'
>
> id = Column(Integer, primary_key=True)
> bs = relationship("B")
>
> class B(Base):
> __tablename__ = 'b'
>
> id = Column(Integer, primary_key=True)
> a_id = Column(Integer, ForeignKey('a.id'))
>
> e = create_engine("sqlite://", echo=True)
>
> Base.metadata.create_all(e)
>
> sess = Session(e)
> a1 = A()
> a1.bs = [B()]
>
> # hold onto the collection
> collection = a1.bs
>
> sess.add(a1)
>
> # "collection" is now no longer associated with a1
> sess.commit()
>
> # emits the warning
> collection.append(B())
>
>
>
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