On Fri, Aug 3, 2018 at 3:29 PM, Derek Lambert <[email protected]> wrote:
> When deleting a child object in a one-to-many relationship retrieved with
> the raiseload('*') query option an exception is raised. Adding
> passive_deletes=True to the relationship on the child prevents the
> exception, but that seems like a hack.
>
> I can remove the option from the query, but I'm trying to understand the
> behavior here. Is this expected?
haven't seen that before but it probably is correct. though
inconvenient. the raiseload is because you want to prevent anyone
accessing that attribute if it wasn't eager loaded. so...the flush
here is trying to hit it as well, because it needs to load it in order
to know what it's deleting. unless you use passive_deletes=True with
ON DELETE CASCADE. Seems like it is doing the job of alerting you to
a SELECT you've said you don't want it to do.
so...maybe?
>
>
> import sqlalchemy as sa
> import sqlalchemy.orm as orm
> from sqlalchemy.ext.declarative import declarative_base
>
>
> Base = declarative_base()
>
>
> class Person(Base):
> id = sa.Column(sa.Integer, autoincrement=True,
> primary_key=True)
> category_id = sa.Column(sa.Integer, sa.ForeignKey('category.id'),
> nullable=False)
> name = sa.Column(sa.String)
>
> category = orm.relationship('Category', back_populates='persons',
> innerjoin=True)
>
> __tablename__ = 'person'
>
>
> class Category(Base):
> id = sa.Column(sa.Integer, autoincrement=True, primary_key=True)
> name = sa.Column(sa.String, unique=True)
>
> persons = orm.relationship('Person', back_populates='category')
>
> __tablename__ = 'category'
>
>
> engine_url = 'postgresql+psycopg2://postgres@localhost/test_test'
> engine = sa.create_engine(engine_url, echo=True)
>
> engine.execute('DROP TABLE IF EXISTS "person"')
> engine.execute('DROP TABLE IF EXISTS "category"')
>
> Base.metadata.create_all(engine)
>
> session = orm.sessionmaker(bind=engine)()
> category1 = Category(name='Category1')
> session.add(category1)
> session.commit()
> session.flush()
>
> person = Person(category=category1, name='Some guy')
> session.add(person)
> session.commit()
> session.flush()
>
> session.expunge_all()
>
> person = session.query(Person).filter(Person.name == 'Some
> guy').options(orm.raiseload('*')).one()
>
> session.delete(person)
> session.commit()
>
> This raises:
>
> Traceback (most recent call last):
> File "/Users/dereklambert/Development/test/misc/test_raise_load.py", line
> 52, in <module>
> session.commit()
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/session.py",
> line 943, in commit
> self.transaction.commit()
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/session.py",
> line 467, in commit
> self._prepare_impl()
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/session.py",
> line 447, in _prepare_impl
> self.session.flush()
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/session.py",
> line 2254, in flush
> self._flush(objects)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/session.py",
> line 2380, in _flush
> transaction.rollback(_capture_exception=True)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py",
> line 66, in __exit__
> compat.reraise(exc_type, exc_value, exc_tb)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/util/compat.py",
> line 249, in reraise
> raise value
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/session.py",
> line 2344, in _flush
> flush_context.execute()
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py",
> line 370, in execute
> postsort_actions = self._generate_actions()
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py",
> line 329, in _generate_actions
> if action.execute(self):
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py",
> line 463, in execute
> prop_has_changes(uow, delete_states, True) or
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/dependency.py",
> line 234, in prop_has_changes
> passive)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/unitofwork.py",
> line 225, in get_attribute_history
> attributes.LOAD_AGAINST_COMMITTED)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py",
> line 753, in get_history
> current = self.get(state, dict_, passive=passive)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py",
> line 597, in get
> value = callable_(state, passive)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/strategies.py",
> line 834, in __call__
> return strategy._load_for_state(state, passive)
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/strategies.py",
> line 589, in _load_for_state
> self._invoke_raise_load(state, passive, "raise")
> File
> "/Users/dereklambert/Development/test/venv/lib/python3.6/site-packages/sqlalchemy/orm/strategies.py",
> line 564, in _invoke_raise_load
> "'%s' is not available due to lazy='%s'" % (self, lazy)
> sqlalchemy.exc.InvalidRequestError: 'Person.category' is not available due
> to lazy='raise'
>
> --
> 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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