I'm sorry you're getting bit by this messaging - but also glad that I'm not
the only one. This got me a while ago too.
SqlAlchemy just uses a bare field name when emitting the warning and
accepting the `overlaps` arguments. In more complex models with 3+ tables
that have standardize relationship names, it's hard to tell what caused the
issue and fixing one relationship can unknowingly affect others.
There is a related ticket/PR. I'm not sure if you can pull it against the
current main branch, but you can do a manual patch of the warnings code
locally to make the output better:
https://github.com/sqlalchemy/sqlalchemy/issues/7309 - Make the
overlaps arguments use fully-qualified names
There's also a related ticket to improve the errors when not calling
`configure_mappers` as
above: https://github.com/sqlalchemy/sqlalchemy/issues/7305
On Thursday, March 10, 2022 at 12:27:33 PM UTC-5 Michael Merickel wrote:
> Thank you Mike. Really appreciate you unpacking my rambling. This works
> for me. I found a few spots in our codebase where we were relying on
> append() working because it really was a simple link table but I rewrote
> them to just create the link manually and add it to the session which also
> causes them to appear in the lists.
>
> On Thu, Mar 10, 2022 at 9:17 AM Mike Bayer
> wrote:
>
>> hey there.
>>
>> The warnings go away entirely by making Parent.children viewonly=True,
>> which for this type of mapping is recommended:
>>
>> class Parent(Base):
>> __tablename__ = "left"
>> id = Column(Integer, primary_key=True)
>> children = relationship(
>> "Child", secondary=Association.__table__, backref="parents",
>> viewonly=True
>>
>> )
>>
>>
>> you wouldn't want to append new records to Parent.children because that
>> would create invalid Association rows (missing extra_data).
>>
>> The warning box at the end of
>> https://docs.sqlalchemy.org/en/14/orm/basic_relationships.html#association-object
>>
>> discusses this situation and the desirability of making the relationship
>> which includes "secondary" as viewonly=True.
>>
>> hope this helps
>>
>>
>> On Wed, Mar 9, 2022, at 8:09 PM, Michael Merickel wrote:
>>
>> Sorry for the rambling, it's been difficult for me to figure out what
>> question to ask because I'm so confused. Below is the minimum viable
>> example that produces no warnings with respect to the overlaps flags and I
>> cannot explain hardly any of them. For example, why does Child.parents
>> require "child_links,parent,child"? 3 values that seem to be somewhat
>> unrelated and are at the very least definitely on different models?
>>
>> class Association(Base):
>> __tablename__ = 'association'
>> left_id = Column(ForeignKey('left.id'), primary_key=True)
>> right_id = Column(ForeignKey('right.id'), primary_key=True)
>> extra_data = Column(String(50))
>>
>> parent = relationship('Parent', back_populates='child_links')
>> child = relationship('Child', back_populates='parent_links')
>>
>> class Parent(Base):
>> __tablename__ = 'left'
>> id = Column(Integer, primary_key=True)
>>
>> children = relationship(
>> 'Child',
>> secondary=Association.__table__,
>> back_populates='parents',
>> overlaps='child,parent',
>> )
>> child_links = relationship(
>> 'Association',
>> back_populates='parent',
>> overlaps='children',
>> )
>>
>> class Child(Base):
>> __tablename__ = 'right'
>> id = Column(Integer, primary_key=True)
>>
>> parents = relationship(
>> 'Parent',
>> secondary=Association.__table__,
>> back_populates='children',
>> overlaps='child_links,parent,child',
>> )
>> parent_links = relationship(
>> 'Association',
>> back_populates='child',
>> overlaps='children,parents',
>> )
>>
>>
>> On Wed, Mar 9, 2022 at 4:50 PM Michael Merickel
>> wrote:
>>
>> I think ultimately I want the overlaps config but reading through
>> https://docs.sqlalchemy.org/en/14/errors.html#relationship-x-will-copy-column-q-to-column-p-which-conflicts-with-relationship-s-y
>>
>> it doesn't make any sense to me what the values in the overlaps= argument
>> are referring to. For example in last snippet that was simpler, what is
>> overlaps='parent' referring to? Neither the Parent object, nor the Child
>> object has something named "parent" so other than blinding trusting the
>> warning I'm unclear how to see what the mapper is building that conflicts
>> here.
>>
>> On Wed, Mar 9, 2022 at 4:33 PM Michael Merickel
>> wrote:
>>
>> It's probably worth noting I can narrow it down to a single warning with
>> the following snippet and it's still unclear to me how to resolve this:
>>
>> class Association(Base):
>> __tablename__ = 'association'
>> left_id = Column(ForeignKey('left.id'), primary_key=True)
>> right_id = Column(ForeignKey('right.id'), primary_key=True)
>>
