that said, I'm looking at this as a potential bug because it should be able to
leave this attribute alone, not really sure how this should be handled.
On Fri, Nov 22, 2019, at 9:21 AM, Mike Bayer wrote:
> lazy="raise" on a many to one is problematic because a lot of many-to-one
> operations involve pulling up the object from the identity map, and that's
> it. since people are usually only trying to guard against SQL being emitted,
> use the raise_on_sql option instead:
>
> parent = relationship(Parent, lazy='raise_on_sql')
>
> thanks for the perfect test case BTW makes this very easy for me
>
> On Fri, Nov 22, 2019, at 6:12 AM, Marat Sharafutdinov wrote:
>> from sqlalchemy import Column, ForeignKey, Integer, create_engine
>> from sqlalchemy.ext.declarative import declarative_base
>> from sqlalchemy.orm import relationship, sessionmaker
>>
>> Base = declarative_base()
>>
>> class Parent(Base):
>> __tablename__ = 'parents'
>> id = Column(Integer, primary_key=True)
>>
>> class Child(Base):
>> __tablename__ = 'children'
>> id = Column(Integer, primary_key=True)
>> parent_id = Column(Integer, ForeignKey(Parent.id))
>> parent = relationship(Parent, lazy='raise', passive_deletes=True)
>>
>> engine = create_engine('sqlite:///:memory:', echo=True)
>> Base.metadata.create_all(engine)
>> Session = sessionmaker(bind=engine)
>> session = Session()
>>
>> # Add
>> parent = Parent()
>> session.add(parent)
>> session.flush()
>> child = Child(parent_id=parent.id)
>> session.add(child)
>> session.commit()
>>
>> # Delete
>> child = session.query(Child).first()
>> session.delete(child)
>> session.commit()
>>
>> Now I'm getting the following warning:
>> /.venv/lib/python3.8/site-packages/sqlalchemy/orm/relationships.py:2021:
>> SAWarning: On Child.parent, 'passive_deletes' is normally configured on
>> one-to-many, one-to-one, many-to-many relationships only.
>>
>> If I change `parent` relationship as follows:
>> parent = relationship(Parent, lazy='raise', backref=backref('children',
>> passive_deletes=True))
>> then I would get the following exception:
>> sqlalchemy.exc.InvalidRequestError: 'Child.parent' is not available due to
>> lazy='raise'
>>
>> How should it be made properly?
>>
>> --
>> 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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>
>
> --
> 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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--
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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