hello.
i'm testing next level of complexity - 3 level inheritance.
C inherits B inherits A, all via table-inheritance, no relations.
A,B are with polymorphic mappers via unions.
e.g. A=Employee, B=Engineer, C=Manager.

The problem is: i cannot query the base polymorphic mapper A.
querying B and C is ok (as well as any other levels above, and/or 
non-polymorphic mappers on all levels).

The error is:
sqlalchemy.exceptions.NoSuchColumnError: 
"Could not locate column in row for column 'pu_Engineer.atype'

(Engineer is level B in this case.)

-----------
Also, we've noticed (well, postgres did it), that the most internal 
select (for that same B-level) of the polymorphic_union has 2 "xxx.id 
AS id" columns:

SELECT "pu_Engineer".machine AS 
pu_Engineer_machine, "pu_Engineer".atype AS 
pu_Engineer_atype, "pu_Engineer".name AS pu_Engineer_name, 
pu_Engineer.duties AS "pu_Engineer_duties", "pu_Engineer".id AS 
pu_Engineer_id
FROM (
   SELECT "Engineer".machine AS machine,
                "Employee".atype AS atype, "Employee".name AS name,
                "Manager".duties AS duties, "Manager".id AS id
   FROM "Employee" JOIN "Engineer" ON "Employee".id = "Engineer".id
        JOIN "Manager" ON "Engineer".id = "Manager".id
 UNION ALL
   SELECT anon.machine AS machine, anon.atype AS atype, anon.name AS 
               name, CAST(NULL AS TEXT) AS duties, anon.id AS id
   FROM (
      SELECT "Employee".name AS name, "Employee".id AS
                      id, "Employee".atype AS atype,
             "Engineer".machine AS machine, "Engineer".id AS id
      FROM "Employee" JOIN "Engineer" ON "Employee".id = "Engineer".id
      WHERE "Employee".atype = ?
   ) AS anon
) AS "pu_Engineer" ORDER BY "pu_Engineer".oid
-------------

see/run attached file

ciao
svil

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Attachment: sa_ABC_inh1.py
Description: application/python

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