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 <mmeri...@gmail.com> 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 <mmeri...@gmail.com>
> 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)
>> extra_data = Column(String(50))
>>
>> parent = relationship('Parent')
>>
>> class Parent(Base):
>> __tablename__ = 'left'
>> id = Column(Integer, primary_key=True)
>> children = relationship('Child', secondary=Association.__table__)
>>
>> class Child(Base):
>> __tablename__ = 'right'
>> id = Column(Integer, primary_key=True)
>>
>> foo.py:24: SAWarning: relationship 'Parent.children' will copy column
>>> left.id to column association.left_id, which conflicts with
>>> relationship(s): 'Association.parent' (copies left.id to
>>> association.left_id). If this is not the intention, consider if these
>>> relationships should be linked with back_populates, or if viewonly=True
>>> should be applied to one or more if they are read-only. For the less common
>>> case that foreign key constraints are partially overlapping, the
>>> orm.foreign() annotation can be used to isolate the columns that should be
>>> written towards. To silence this warning, add the parameter
>>> 'overlaps="parent"' to the 'Parent.children' relationship. (Background on
>>> this error at: https://sqlalche.me/e/14/qzyx)
>>
>>
>> On Wed, Mar 9, 2022 at 4:31 PM Michael Merickel <mmeri...@gmail.com>
>> wrote:
>>
>>> I have looked at the couple examples in the docs (many-to-many, and
>>> association table) and have noticed that my codebase has a slightly
>>> different pattern which is causing warnings when upgrading to 1.4. I'm
>>> trying to figure out the best pattern to accomplish what I've been doing
>>> which doesn't match the docs exactly.
>>>
>>> In the below example you can see that there are backrefs on all of the
>>> links, and that there are backrefs from the link table to the related
>>> objects, as well as a secondary link from Parent to Child via
>>> Parent.children and Child.parents.
>>>
>>> There seem to be several options and I'm struggling to figure out what
>>> the solution should be to maintain the behavior with all of the following
>>> relationships working:
>>>
>>> - Parent.children
>>> - Parent.child_links
>>> - Child.parents
>>> - Child.parent_links
>>> - Association.parent
>>> - Association.child
>>>
>>> Code and warnings are below:
>>>
>>> from sqlalchemy import Column, ForeignKey, String, Integer
>>> from sqlalchemy.orm import configure_mappers, relationship
>>> from sqlalchemy.ext.declarative import declarative_base
>>>
>>> Base = declarative_base()
>>>
>>> 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', backref='child_links')
>>> child = relationship('Child', backref='parent_links')
>>>
>>> class Parent(Base):
>>> __tablename__ = 'left'
>>> id = Column(Integer, primary_key=True)
>>> children = relationship('Child', secondary=Association.__table__,
>>> backref='parents')
>>>
>>> class Child(Base):
>>> __tablename__ = 'right'
>>> id = Column(Integer, primary_key=True)
>>>
>>> configure_mappers()
>>>
>>> foo.py:25: SAWarning: relationship 'Child.parents' will copy column
>>>> right.id to column association.right_id, which conflicts with
>>>> relationship(s): 'Association.child' (copies right.id to
>>>> association.right_id), 'Child.parent_links' (copies right.id to
>>>> association.right_id). If this is not the intention, consider if these
>>>> relationships should be linked with back_populates, or if viewonly=True
>>>> should be applied to one or more if they are read-only. For the less common
>>>> case that foreign key constraints are partially overlapping, the
>>>> orm.foreign() annotation can be used to isolate the columns that should be
>>>> written towards. To silence this warning, add the parameter
>>>> 'overlaps="child,parent_links"' to the 'Child.parents' relationship.
>>>> (Background on this error at: https://sqlalche.me/e/14/qzyx)
>>>> configure_mappers()
>>>> foo.py:25: SAWarning: relationship 'Child.parents' will copy column
>>>> left.id to column association.left_id, which conflicts with
>>>> relationship(s): 'Association.parent' (copies left.id to
>>>> association.left_id), 'Parent.child_links' (copies left.id to
>>>> association.left_id). If this is not the intention, consider if these
>>>> relationships should be linked with back_populates, or if viewonly=True
>>>> should be applied to one or more if they are read-only. For the less common
>>>> case that foreign key constraints are partially overlapping, the
>>>> orm.foreign() annotation can be used to isolate the columns that should be
>>>> written towards. To silence this warning, add the parameter
>>>> 'overlaps="child_links,parent"' to the 'Child.parents' relationship.
>>>> (Background on this error at: https://sqlalche.me/e/14/qzyx)
>>>> configure_mappers()
>>>> foo.py:25: SAWarning: relationship 'Parent.children' will copy column
>>>> left.id to column association.left_id, which conflicts with
>>>> relationship(s): 'Association.parent' (copies left.id to
>>>> association.left_id), 'Parent.child_links' (copies left.id to
>>>> association.left_id). If this is not the intention, consider if these
>>>> relationships should be linked with back_populates, or if viewonly=True
>>>> should be applied to one or more if they are read-only. For the less common
>>>> case that foreign key constraints are partially overlapping, the
>>>> orm.foreign() annotation can be used to isolate the columns that should be
>>>> written towards. To silence this warning, add the parameter
>>>> 'overlaps="child_links,parent"' to the 'Parent.children' relationship.
>>>> (Background on this error at: https://sqlalche.me/e/14/qzyx)
>>>> configure_mappers()
>>>> foo.py:25: SAWarning: relationship 'Parent.children' will copy column
>>>> right.id to column association.right_id, which conflicts with
>>>> relationship(s): 'Association.child' (copies right.id to
>>>> association.right_id), 'Child.parent_links' (copies right.id to
>>>> association.right_id). If this is not the intention, consider if these
>>>> relationships should be linked with back_populates, or if viewonly=True
>>>> should be applied to one or more if they are read-only. For the less common
>>>> case that foreign key constraints are partially overlapping, the
>>>> orm.foreign() annotation can be used to isolate the columns that should be
>>>> written towards. To silence this warning, add the parameter
>>>> 'overlaps="child,parent_links"' to the 'Parent.children' relationship.
>>>> (Background on this error at: https://sqlalche.me/e/14/qzyx)
>>>> configure_mappers()
>>>
>>>
>>> Thanks!
>>>
>>> --
>>>
>>> Michael
>>>
>>
>>
>> --
>>
>> Michael
>>
>
>
> --
>
> Michael
>
--
Michael
--
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
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