im not a huge fan of cascade_mapper for reasons like this.
since you have an ambiguous join, perhaps youre looking for explicit
join conditions ?
http://www.sqlalchemy.org/docs/
adv_datamapping.myt#adv_datamapping_relations_customjoin
On Mar 26, 2006, at 1:05 PM, Gambit wrote:
Hi guys -
I'm not sure this is a bug or not, but if not it might be worth
adding a comment to the documentation.
Using the following schema:
table A:
pk
B_fk_1
B_fk_2
...
table B:
pk
info
After setting up A and B correctly (see attachment), and performing
cascade_mapper(A, B), looking at an instance of class A does not
show any B instances (nor is it unambiguous what they should be
called). There is, I note, a A.B entry, but with the value of
None. Looking at the engine log, it is obvious what is happening -
it is trying to find the B object which has a pk matching both
B_fk_1 AND B_fk_2.
The documentation for cascade_mapper should be updated to either
state that it's not the right tool for this situation, or perhaps a
bug/feature request filed against cascade_mapper.
Incidentally, I am trying, as you can see from the attached larger
sample, to build up to a correctly specified mapper for this
testcase. This information may be in the docs already (if anyone
wants to submit chapter and verse...?).
Cheers!
--G
<multiple_join_test.sql>
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