[Sqlalchemy-tickets] Issue #3856: Query.union producing query with polymorphic discriminator when not appropriate (zzzeek/sqlalchemy)

[Oliver R. <iss...@bi...>]

New issue 3856: Query.union producing query with polymorphic discriminator when not appropriate
https://bitbucket.org/zzzeek/sqlalchemy/issues/3856/queryunion-producing-query-with

Oliver Rutherfurd:

a.union(b) is unnecessarily including polymorphic discriminator when a and b contain columns from a polymorphic subclass, whereas union(a, b) does not.  The result is cartesian product from a.union(b).  A demo file is attached.