On Jan 8, 2014, at 5:41 PM, Russell Holloway <russ.d.hollo...@gmail.com> wrote:
> Hello all, > > I keep hitting an assertion error, "Dependency Rule Tried To Blank Out > Primary Key..." when trying to remove all children using an association > object. > > My situation seems very similar to > https://groups.google.com/forum/#!topic/sqlalchemy/3g4__pFHZTs > > However, based on Michaels response, it sounds like we must delete both > objects, which I don't want to do since it is a many-many relationship. Below > is a simple equivalent to my code: > > Page(Object): > page_id = Column(Integer, primary_key = True) > title = Column(String) > > user_relationships = relationship(Page_to_User) > > User(Object): > user_id = Column(Integer, primary_key = True) > name = Column(String) > > Page_to_User(Object): > > page_id = Column(Integer, ForeignKey(Page.page_id), primary_key = True) > user_id = Column(Integer, ForeignKey(User.user_id), primary_key = True) > relationship_type = (Integer, ForeignKey(Relationship.type_id), primary_key > = True) > > page = relationship(Page) > user = relationship(User) you need to put a cascade rule on Page.user_relationships, such that when you remove a Page_to_User from the collection, it’s marked as deleted, instead of SQLAlchemy setting the page_id foreign key to NULL, which is invalid here b.c. that column is part of the primary key (and hence the error). Page_to_User can’t exist in the database without being referred to by a Page object since the primary key would be NULL. the delete-orphan cascade is introduced at: http://docs.sqlalchemy.org/en/rel_0_9/orm/tutorial.html#configuring-delete-delete-orphan-cascade and some more information at: http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html#deleting-from-collections > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/groups/opt_out.
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