Simon, thanks for the suggestion with association proxies I used them once
in the past.
Richard, I see your point this design might indeed have some unintended
consequence.
As I mentioned in the first message I am aware that it's an unusual
approach and this is a deliberate choice. I just wanted to know if it's
possible to set up this kind of relationships using *primaryjoin* without
having *secondary* table.
I did some digging in the source code and I think that it's not possible to
define *MANYTOMANY* with *back_populates* without using *secondary* table,
cause of the following:
if (
self.direction in (ONETOMANY, MANYTOONE)
and self.direction == other.direction
):
raise sa_exc.ArgumentError(
"%s and back-reference %s are "
"both of the same direction %r. Did you mean to "
"set remote_side on the many-to-one side ?"
% (other, self, self.direction)
)
I managed to use:
companies = relationship(
"Company",
foreign_keys="Company.address_id",
primaryjoin=(
"Company.address_id == Address.address_id"
),
viewonly=True
)
and:
addresses = relationship(
"Address",
foreign_keys="Address.address_id",
primaryjoin=(
"Address.address_id == Company.address_id"
),
viewonly=True
)
Even with *viewonly=True* it appears that I can still mutate the
*InstrumentedList*, but as far as I understand the changes SQLAlchemy will
not try to persist the operations, right?
Sadly, I still don't really know the meaning of *foreign()* and *remote() *and
how to use confidently.
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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