On Wed, Mar 18, 2020, at 11:22 AM, Tony Hignett wrote: > Hi, > > I'm trying to upgrade from 1.2.2 to 1.3.15 and a number of our relations have > started generating these warnings: > ``` > SAWarning: Setting backref / back_populates on relationship <child.parent> to > refer to viewonly relationship <parent.children> will be deprecated in > SQLAlchemy 1.4, and will be disallowed in a future release. viewonly > relationships should not be mutated (this warning may be suppressed after 10 > occurrences) > (self, other), > ``` > > I've read some of the related issues, e.g. > https://github.com/sqlalchemy/sqlalchemy/issues/5149, > https://github.com/sqlalchemy/sqlalchemy/issues/ > <https://github.com/sqlalchemy/sqlalchemy/issues/5149>4993, but I don't > understand how backref comes into it. We don't want to mutate anything along > the backref. > > Is there a way of expressing a two-way read-only relation?
you should remove the backref. have the "viewonly" relationship stand alone by itself. > > The code looks like > ``` > class Parent(Base): > pass > > class Child1(Base): > > @declared_attr > def parent(cls): > return orm.relationship( > Parent, > ..., > viewonly=True, > backref="children1" > ) > > class Child2(Base): > [etc] > ```` > > -- > 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. > --- > 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 view this discussion on the web visit > https://groups.google.com/d/msgid/sqlalchemy/660cedf0-7066-42fe-93bc-d6e4d223b05c%40googlegroups.com > > <https://groups.google.com/d/msgid/sqlalchemy/660cedf0-7066-42fe-93bc-d6e4d223b05c%40googlegroups.com?utm_medium=email&utm_source=footer>. -- 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. --- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sqlalchemy/40c0410d-0233-4abc-aae7-bfe728495647%40www.fastmail.com.
