Please provide all mappings including the missing "Prestacion" class
as well as exact information on which classes have their own tables or
not. The code should be a mappings I can paste into a .py file and
run to see the error you are getting.
On Mon, Sep 11, 2017 at 11:38 AM, Julio César Gázquez
<julio_li...@mebamutual.com.ar> wrote:
> Hi list.
>
> I guess I messed it.
>
> I built an app on the premise I can build two different relationships
> relying on the same field. My data model is basically as below. Class
> names are roughly translated from Spanish. Please read comments in
> Charge subclasses to grasp the problem.
>
> class Affiliate(Base):
>
> id = Column(Integer, primary_key=True)
> ...
>
> class AffiliateFamilyMember(Base)
> affiliate_id = Column(Integer, primary_key=True)
> family_member_no = Column(SmallInteger, primary_key=True)
>
>
> class Charge(Base):
>
> id = Column(Integer, primary_key=True)
> affiliate_id = Column(Integer, ForeignKey('socios.id'), nullable=False)
> family_member_no = Column(SmallInteger)
>
> affiliate = relationship('Affiliate',
> foreign_keys='Prestacion.affiliate_id')
> family_member = relationship('AffiliateFamilyMember',
> foreign_keys='[Prestacion.affiliate_id,
> Prestacion.family_member_no]')
> ...
>
>
> # Charge has a lot of subclasses like those
> class LoanCharge(Charge):
>
> # Only affiliates can have loans.
> # affiliate attribute is set to the Affiliate instance
> # family_member attribute has no sense in this case
> ...
>
>
> class PharmacyPurchase(Charge):
> # Any family member of affiliates can do farmacy purchases.
> # family_member is set to the AffiliateFamilyMember instance
> # affiliate is a valid read-only attribute on persisted instances
> # as Affiliate.id == AffiliateFamilyMember.affiliate_id
>
>
> Being a bit awkward, It worked well and silently on SQLAlchemy 0.8.x and
> 0.9.x. I went into production using 0.9.x.
>
> But when using 1.x versions I got:
>
> SAWarning: relationship 'Charge.family_member' will copy column
> affiliate_family_members.affiliate_id to column
> charges.affiliate_id, which conflicts with relationship(s):
> 'Charge.affiliate' (copies affiliates.id to charges.affiliate_id).
> Consider applying viewonly=True to read-only relationships, or
> provide a primaryjoin condition marking writable columns
> with the foreign() annotation.
>
> Besides being a warning, I'm not sure if this actually can broke
> something (Some problems I got trying to use 1.0.x days made me think
> so). So I tried to fix it, but it's not as easy as it seemed.
>
> The gist is that in certain Charge subclasses I need affiliate being a
> regular relationship, in other subclasses I need affiliate being a
> "viewonly" relationship. But as all subclasses share the same mapper,
> relationships from different subclasses clash one with each other:
>
> SAWarning: relationship 'PharmacyPurchase.family_member will copy
> column family_members.affiliate_id to column
> charges.affiliate_id which conflicts with relationship(s):
> 'LoanCharge.affiliate' (copies affiliates.id to charges.affiliate_id).
> Consider applying viewonly=True to read-only relationships, or
> provide a primaryjoin condition marking writable columns
> with the foreign() annotation.
>
> I'm not sure there is really a solution, besides using separate fields
> for both relationships, as that should be an endeavor I'd rather avoid.
>
> Any suggestions?
>
> Thanks in advance.
>
> Greetings.
>
> Julio.
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
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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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