there's an FAQ entry, a little bit dated but the general idea is still there, 
at:

https://docs.sqlalchemy.org/en/13/faq/ormconfiguration.html#i-m-getting-a-warning-or-error-about-implicitly-combining-column-x-under-attribute-y

for joined table inheritance, where Name(Node) -> node_id are FK -> PK, the 
warning isn't emitted.  so please share the mapping if it is doing this when it 
shouldnt.


On Wed, Sep 2, 2020, at 9:08 PM, Richard Damon wrote:
> I am getting the following error:
> 
> SAWarning: Implicitly combining column Node.node_id with column
> Name.node_id under attribute 'node_id'.  Please configure one or more
> attributes for these same-named columns explicitly.
> 
> In my case I am using poymorphic classes by joining with the ORM. Node
> is the base of the hierarchy (derived from declarative_base), then I
> have a class Property derived from it, and a class Name derived from
> Property. Each class has a primary_key named node_id, with a foreign key
> constraint one step done the hierarchy. I have also tried making all the
> Foreign key constraints point to Node.node_id and it doesn't make a
> difference.
> 
> It is just a warning, and the lookup does seem to make the double join,
> so it doesn't seem to be a big problem, but it seems it want me to
> configure something for these, but I am not sure what.
> 
> Two level inheritance is working just fine, it is just where it hits the
> 3rd level that it seems to want something explicit.
> 
> -- 
> Richard Damon
> 
> -- 
> SQLAlchemy - 
> The Python SQL Toolkit and Object Relational Mapper
> 
> http://www.sqlalchemy.org/
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