On Wed, Jan 10, 2018 at 1:03 PM, Matt Schmidt <slo...@gmail.com> wrote:
> I have a small companion library that I wrote for model-to-dict
> serialization. I just updated to 1.2.0 and one of my tests is failing --
>
> https://gitlab.com/sloat/SerialAlchemy/blob/master/tests/test_to_dict.py#L193
>
> In 1.1.x, it worked as expected, but in 1.2, the primary-key is added to the
> serialized profile field. So the output is now:
>
> {
> 'firstname': 'test',
> 'profile': {
> 'id': 3,
> 'somefield': 'somevalue'
> },
> }
>
>
> I just wanted to make sure this is expected behavior from SQLAlchemy. It's
> not a problem for me to update the test, it won't impact the actual
> functionality of the library.
>From making a test (below) I can see this behavior changed within the
1.1 series, not in 1.2. Up through 1.1.13 it gets:
{'_sa_instance_state': <sqlalchemy.orm.state.InstanceState object at
0x7f8046c5df90>, 'data': u'a'}
in 1.1.14 it becomes:
{'_sa_instance_state': <sqlalchemy.orm.state.InstanceState object at
0x7f1e0d217e50>, 'data': u'a', 'id': 1}
A bisect brings us to:
https://bitbucket.org/zzzeek/sqlalchemy/issues/4048
this shows there was a bug with undeferral as coming off of a joined
eager load, where the keys to be "undeferred" weren't being acted upon
properly. pdbing into the example shows that the "id" attribute is
being loaded when load_only() is used, but the bug fixed in 4048 is
preventing the attribute from being populated onto the object
properly. This implies that the primary key attributes are loaded
even when load_only() seems to exclude them, and that this is the
normally established behavior, here not occurring due to a bug.
This can be confirmed if we change the joinedload to lazyload:
a1 = s.query(A).options(lazyload(A.bs).load_only('data')).one()
print a1.bs[0].__dict__
in an early 1.1 version 1.1.5, we get "id":
{'_sa_instance_state': <sqlalchemy.orm.state.InstanceState object at
0x7fddb21cffd0>, 'data': u'a', 'id': 1}
therefore the bug fixed in 4048, while it wasn't testing for this
specific condition, is repairing the deferral rules for attributes
coming off of a joinedload, and under that repair the primary key
attributes are now being populated as would be the case when
load_only() is used in other contexts.
This is not to say that the primary key attributes being present under
load_only() is a desirable feature, only that this is how it seems to
have been working overall, and the change here is repairing a bug that
was masking the attribute from completing its population.
On your end I would recommend making your test not depend on the
primary key attributes being there or not so that changes here won't
break your tests.
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(ForeignKey('a.id'))
data = Column(String)
e = create_engine("sqlite://", echo=True)
Base.metadata.create_all(e)
s = Session(e)
s.add(A(bs=[B(data='a'), B(data='b')]))
s.commit()
a1 = s.query(A).options(joinedload(A.bs).load_only('data')).one()
print a1.bs[0].__dict__
>
> -Matt
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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