there are deferred() columns that you can set on a mapper but there's not a
mechanism right now to set deferred target attributes when the object is loaded
only from a specific relationship without the specific call within the query().
So unless you maybe ran those options into every Query unconditionally, or
something. I'd look to see how big a deal it is to just be explicit on this
one.
On May 14, 2014, at 1:39 PM, Seth <seedifferen...@gmail.com> wrote:
> Thanks Mike,
>
> But...is there no way to set this behavior directly on the "relationship()"?
> The whole point there is to be "lazy" ;)
>
> Seth
>
>
>
> On Saturday, May 10, 2014 7:59:33 PM UTC-7, Michael Bayer wrote:
> session.query(Parent).options(defaultload("children").load_only("cheap_column"))
>
> or really if you want to cut out "expensive_column"
>
> session.query(Parent).options(defaultload("children").defer("expensive_column"))
>
> http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#deferred
>
>
>
> On May 10, 2014, at 6:39 PM, Seth <seediff...@gmail.com> wrote:
>
>> Is there any way to get SQLAlchemy to only load specific columns through a
>> relationship()?
>>
>> For example, with this scenario:
>>
>> class Parent(Base):
>> __tablename__ = 'parent'
>> id = Column(Integer, primary_key=True)
>> children = relationship("Child", lazy='joined')
>>
>> class Child(Base):
>> __tablename__ = 'child'
>> id = Column(Integer, primary_key=True)
>> parent_id = Column(Integer, ForeignKey('parent.id'))
>> cheap_column = Column(Unicode(10))
>> expensive_column = Column(LargeBinary)
>>
>> I'd like Child to get lazily joined when Parent is loaded, but only with
>> Child's "cheap_column" and not it's "expensive_column".
>>
>> Thanks,
>> Seth
>>
>>
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