sqlalchemy 中的多对多自引用关系
我试图在 sqlalchemy 中建立自引用多对多关系（这意味着 Line 可以有许多父行和许多子行），如下所示：
Base = declarative_base()
class Association(Base):
__tablename__ = 'association'
prev_id = Column(Integer, ForeignKey('line.id'), primary_key=True)
next_id = Column(Integer, ForeignKey('line.id'), primary_key=True)
class Line(Base):
__tablename__ = 'line'
id = Column(Integer, primary_key = True)
text = Column(Text)
condition = Column(Text)
action = Column(Text)
next_lines = relationship(Association, backref="prev_lines")
class Root(Base):
__tablename__ = 'root'
name = Column(String, primary_key = True)
start_line_id = Column(Integer, ForeignKey('line.id'))
start_line = relationship('Line')
但出现以下错误： sqlalchemy.exc.ArgumentError：无法确定父/之间的连接条件 关系 Line.next_lines 上的子表。指定“primaryjoin”表达式 名词如果存在“Secondary”，则还需要“SecondaryJoin”。
你知道我该如何解决这个问题吗？
I'm trying to make a self-referential many-to-many relationship (it means that Line can have many parent lines and many child lines) in sqlalchemy like this:
Base = declarative_base()
class Association(Base):
__tablename__ = 'association'
prev_id = Column(Integer, ForeignKey('line.id'), primary_key=True)
next_id = Column(Integer, ForeignKey('line.id'), primary_key=True)
class Line(Base):
__tablename__ = 'line'
id = Column(Integer, primary_key = True)
text = Column(Text)
condition = Column(Text)
action = Column(Text)
next_lines = relationship(Association, backref="prev_lines")
class Root(Base):
__tablename__ = 'root'
name = Column(String, primary_key = True)
start_line_id = Column(Integer, ForeignKey('line.id'))
start_line = relationship('Line')
But I get the following error:
sqlalchemy.exc.ArgumentError: Could not determine join condition between parent/
child tables on relationship Line.next_lines. Specify a 'primaryjoin' expressio
n. If 'secondary' is present, 'secondaryjoin' is needed as well.
Do you know how I could remedy this?
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您应该只需要：
由于这指定了
next_lines反向引用，因此不需要有next_lines关系。您还可以使用关系的
remote_side参数来执行此操作：http://www.sqlalchemy.org/trac/browser/examples/adjacency_list/adjacency_list.pyYou should just need:
Since this specifies the
next_linesback reference there is no need to have anext_linesrelationship.You can also do this using the
remote_sideparameter to a relationship: http://www.sqlalchemy.org/trac/browser/examples/adjacency_list/adjacency_list.py