Hi,

I don't think I understand exactly what I'm supposed to pass to the foreign_keys parameter to relation.

I'm trying to set up a 1-to-many viewonly relation, with no backref, where there are two intermediate tables between the parent table and the child. To complicate things further, I need to restrict the rows by joining against a couple of other tables as well.

I was previously running on a fairly old version of SA (revision 2283), and the relation seemed to work correctly when I ANDed all of my conditions together and passed them to relation as the primaryjoin.

However, I just tried 0.3.6 and got "ArgumentError: Cant locate any foreign key columns ... Specify foreign_keys argument ..."

(Interestingly, if I try 0.3.5, the relation compiles but when I try to access it I get a different exception, InvalidRequestError, about a column not being available because it conflicts with another one)

For example, if these are my tables: #------------------------------------------------------------------ # Three entities, 'a', 'b' and 'c'. # 'a' and 'b' have a many-to-many relationship # 'b' and 'c' have a many-to-many relationship a_table = Table('a', metadata, Column('id', Integer, primary_key=True), Column('name', String(16)), )

b_table = Table('b', metadata, Column('id', Integer, primary_key=True), Column('name', String(16)), )

c_table = Table('c', metadata, Column('id', Integer, primary_key=True), Column('name', String(16)), )

a_b_table = Table('a_b', metadata, Column('a_id', Integer, ForeignKey('a.id'), primary_key=True), Column('b_id', Integer, ForeignKey('b.id'), primary_key=True), ) b_c_table = Table('b_c', metadata, Column('b_id', Integer, ForeignKey('b.id'), primary_key=True), Column('c_id', Integer, ForeignKey('c.id'), primary_key=True) )

class A(object): pass

class B(object): pass

class C(object): pass

mapper(B, b_table) mapper(C, c_table)

############################################################# # How can I create a mapper on A with a property that gives # all the 'C' objects? ############################################################# # This doesn't work - it requires the foreign_keys parameter # to be passed, but I don't know what to pass. mapper( A, a_table, properties={'cs': relation(primaryjoin=and_(a_table.c.id == a_b_table.c.a_id, a_b_table.c.b_id == b_c_table.c.b_id, c_table.c.id == b_c_table.c.c_id), viewonly=True, ) } )

#------------------------------------------------------------------

I probably haven't explained myself very well. I've tried lots of ways of expressing the relation, including passing a select as an association table, but I can't seem to get it to work. Does anyone have any ideas?

Thanks a lot,

Simon