On 07/21/2011 09:20 AM, Ben Sizer wrote:
> I have 2 classes:
>
> Base = declarative_base()
>
> class Parent(Base):
> __tablename__ = 'parent'
> id = Column(Integer, primary_key=True)
> children = relationship("Child", cascade="all")
>
> class Child(Base):
> __tablename__ = 'child'
> id = Column(Integer, primary_key=True)
> parent_id = Column(Integer, ForeignKey('parent.id'),
> nullable=False)
> details = Column(Text(), nullable=False)
>
> I recently added nullable=False to the Child.parent_id column, and now
> the following code produces an error.
>
> p = self.session.query(Parent).filter_by(id=1234).one()
> p.children = [Child(details=x) for x in x_list] # don't think
> content of x_list is relevant
> self.session.commit()
>
> File "C:\Python27\lib\site-packages\sqlalchemy-0.7.1-py2.7.egg
> \sqlalchemy\engine\default.py", line 325, in do_execute
> cursor.execute(statement, parameters)
> IntegrityError: (IntegrityError) child.parent_id may not be NULL
> u'UPDATE child SET parent_id=? WHERE child.id = ?' (None, 1)
>
> Why is it generating this particular UPDATE statement? Shouldn't it
> add the correct parent_id from the Parent object, not None? Even if I
> add 'parent_id=1234' into the Child() constructor, it still attempts
> to set parent_id to None with this UPDATE.
>
> What am I doing wrong?
It means that there is a Child row already in the database with
parent_id=1234. When you reassign p.children to not include that child,
SQLAlchemy detects that the child object is now an orphan (has no
parent). Based on your cascade rules (cascade="all"), SQLAlchemy will
try to NOT delete the child, but instead set its parent_id to NULL (the
only sensible alternative to not deleting the child).
If you want the child to be deleted in this case, change the cascade to
"all,delete-orphan". Otherwise, you need to ensure that the child is
kept in p.children, e.g. p.children += [Child(details=x) for x in x_list].
-Conor
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To post to this group, send email to sqlalchemy@googlegroups.com.
To unsubscribe from this group, send email to
sqlalchemy+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/sqlalchemy?hl=en.
