Thanks for the reply. There is something I don't understand in the example:
B_viacd = mapper(B, j, non_primary=True, properties={
"b_id": [j.c.b_id, j.c.d_b_id],
"d_id": j.c.d_id
})
How Is the mapper supposed to map the results of j with the class B ? the
statement behind j is:
SELECT d.id AS d_id, b.id AS b_id, d.b_id AS d_b_id, d.c_id AS d_c_id, c.id
> AS c_id, c.a_id AS c_a_id
> FROM b JOIN d ON d.b_id = b.id JOIN c ON c.id = d.c_id
d.id is mapped to d_id, and b.id to b_id. So I don't understand how the ORM
can map b.id to B.id.
Le ven. 28 déc. 2018 à 00:25, Mike Bayer <mike...@zzzcomputing.com> a
écrit :
> the section at
> https://docs.sqlalchemy.org/en/latest/orm/join_conditions.html#relationship-to-non-primary-mapper
> has a recipe for: "when we seek to join from A to B, making use of any
> number of C, D, etc. in between, however there are also join
> conditions between A and B directly", I think that's this case because
> you have conditions between Game/YearStadium directly. So I think use
> that pattern.
>
>
>
> On Thu, Dec 27, 2018 at 6:18 AM <mgm...@wiremind.fr> wrote:
> >
> > from sqlalchemy import Column, DateTime, String, Integer, ForeignKey,
> func, Table, create_engine
> > from sqlalchemy.orm import relationship, backref, sessionmaker,
> joinedload, contains_eager
> > from sqlalchemy.ext.declarative import declarative_base
> >
> > Base = declarative_base()
> > engine = create_engine('sqlite://', echo=True)
> >
> >
> > class Game(Base):
> > __tablename__ = 'game'
> >
> > id = Column(Integer, primary_key=True)
> >
> > stadium_name = Column(String)
> > month_id = Column(Integer, ForeignKey('month.id'))
> >
> > year_stadium = relationship("YearStadium", secondary="month",
> > primaryjoin="Month.id == Game.month_id",
> > secondaryjoin="and_(Month.year_name == YearStadium.year_name, "
> > "YearStadium.stadium_name == Game.stadium_name)")
> >
> >
> > class Month(Base):
> > __tablename__ = 'month'
> >
> > id = Column(Integer, primary_key=True)
> >
> > year_name = Column(String)
> >
> >
> > class YearStadium(Base):
> > __tablename__ = 'year_stadium'
> >
> > id = Column(Integer, primary_key=True)
> >
> > stadium_name = Column(String)
> > year_name = Column(String)
> >
> >
> > Base.metadata.drop_all(engine)
> > Base.metadata.create_all(engine)
> > Session = sessionmaker(engine)
> > session = Session()
> >
> >
> > session.query(Game).join(Game.year_stadium).all() # works
> > session.query(Game).options(joinedload(Game.year_stadium)) # fails
> >
> > In the example above, I'm trying to have a relationship to a table. It's
> not a classic association table example, since the third table needs one
> column from table 2 and one column from table 1 to be joined.
> > The relationship I wrote works well for simple joins or when
> lazy-loading, but fails with a joinedload.
> >
> > Is there a way to make it work ?
> >
> > --
> > SQLAlchemy -
> > The Python SQL Toolkit and Object Relational Mapper
> >
> > http://www.sqlalchemy.org/
> >
> > To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
Mehdi GMIRA
Lead Developer - RMPulse
Mail: *mgm...@wiremind.fr <mgm...@wiremind.fr>*
Mobile: +33 6 99 31 56 69
Wiremind SAS
--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
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