Issue with cascade deletion

[Javier Uribe]

Hi, so I have the database classes as follows:

class Thing(Base):


DatasetId = Column(ForeignKey(schema + 'Dataset.DatasetId'), primary_key=True, nullable=False, index=True)

RequiredThing_child = relationship('RequiredThing', cascade='all, delete-orphan')

class Location(Base):


DatasetId = Column(ForeignKey(schema + 'Dataset.DatasetId'), primary_key=True, nullable=False, index=True)

RequiredThing_child = relationship('RequiredThing', cascade='all, delete-orphan')

class RequiredThing(Base):


DatasetId = Column(ForeignKey(schema + 'Dataset.DatasetId'), primary_key=True, nullable=False, index=True)

Thing= relationship('Thing', viewonly=True) Location= relationship('Location', viewonly=True)

(There are more relationships on both tables but these ones are the only ones that I've had issues with, as they both have that column).  

I set them up like that because I want to have the cascade deletion functionality: whenever I call for a deletion of a thing object I want the children (in this case RequiredThing) to be deleted as well (as long as it matches with the Thing Id). When I had it active for only one table (in this case Thing), it worked fine but now that I also added the relationship for the Location table it's giving me the following warning: 

SAWarning: relationship 'Location.RequiredThing_child' will copy column Location.DatasetId to column RequiredThing.DatasetId, which conflicts with relationship: 'Thing.RequiredThing_child' (copies Thing.DatasetId to RequiredThing.DatasetId).

I've tried to add back_populates to the RequiredThing class but to no avail.

I need this to work because I want to implement the cascade functionality to many more tables as needed but I do not want there to be any errors or ambiguity when running the queries.

Or if there's a better way to implement cascade deletion I'm all for it.

Any suggestions or corrections to my code would be greatly appreciated!

Kind regards,

Javier

(reposted to edit the paragraphs)