you've turned off "save-update" cascade so the "c" object is not placed into
the Session when you do the final save() of p.
Fix:
session.add_all(p.children)
p.children = []
save(session, p)
On Nov 17, 2010, at 12:38 PM, Joril wrote:
> from sqlalchemy import Column, String, Integer, Table, ForeignKey
> from sqlalchemy.engine import create_engine
> from sqlalchemy.orm import sessionmaker, relationship
> from sqlalchemy.ext.declarative import declarative_base
>
> Base = declarative_base()
>
> junction = Table("junction", Base.metadata, Column("p_id",
> ForeignKey("parents.id")),
> Column("c_id",
> ForeignKey("children.id")))
>
> class Child(Base):
> __tablename__ = "children"
>
> id = Column(Integer, primary_key=True)
>
> class Parent(Base):
> __tablename__ = "parents"
>
> id = Column(Integer, primary_key=True)
> children = relationship(Child, secondary=junction, cascade="")
>
>
> def save(session, x):
> session.add(x)
> session.flush()
>
> en = create_engine("sqlite:///:memory:", echo=True)
> Base.metadata.create_all(en)
> maker = sessionmaker(en)
> session = maker(autocommit=True)
>
> # Save a child and close the session
> c = Child()
> save(session, c)
> session.close()
>
> # Associate the child to a parent and save
> p = Parent()
> p.children = [c]
> save(session, p)
>
> # Try to remove the child
> p.children = []
> save(session, p)
>
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