g'day.

How one can make such thing as a reference to concrete-inherited 
polymorphic mapper?
e.g. if there are just two, A and B, B inherits A, both have full 
concrete tables. A has polymorphic mapper.

If both tables have separate primary ids, they will overlap as 
values - table_A.id=1 for some A() and table_B.id=1 for some B() are 
both ok; hence, query(A).getby_id(1) would return 2 objects via the 
polymorphic union.
in this case, the unique key within the polymunion seems to be the 
id+type_discriminator; where type_discriminator effectively 
means "this id is from that table".

i see 2 possibilities here:

 - use 2-field key: a tuple of discriminator(table_name) and 
id-in-that-table. How would one make references to those objects 
then? e.g. what would be the definition of Column( 'mylink_id', ...) 
be ? it becomes a link to multiple tables... Would the 
propertyLoaders support such multi-column key? or make some 
constructed single key instead?

 - use one common sequence for filling both primary-keys of both 
tables. But this is limited to DBs which support sequences...

Any help?

ciao
svil

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