我有这样简单的模型:
TableA2TableB = Table('TableA2TableB', Base.metadata,
Column('tablea_id', BigInteger, ForeignKey('TableA.id')),
Column('tableb_id', Integer, ForeignKey('TableB.id')))
class TableA(Base):
__tablename__ = 'TableA'
id = Column(BigInteger, primary_key=True)
infohash = Column(String, unique=True)
url = Column(String)
tablebs = relationship('TableB', secondary=TableA2TableB, backref='tableas')
class TableB(Base):
__tablename__ = 'TableB'
id = Column(Integer, primary_key=True)
url = Column(String, unique=True)
然而,sqla会生成类似
的查询SELECT "TableB".id, "TableB".url AS "TableB_url" FROM "TableB", "TableA2TableB"
WHERE "TableA2TableB".tableb_id = "TableB".id AND "TableA2TableB".tablea_id = 408997;
但是,当选择的属性是TableB
中的属性时,为什么查询中会出现笛卡尔积?不应该TableA2TableB
。
由于
答案 0 :(得分:0)
就像现在一样,TableB(tableas)中存在一个backref关系并加载它,因为默认加载模式设置为select。
您可能希望将TableA.tablebs更改为
tablebs = relationship('TableB', secondary=TableA2TableB, backref='tableas', lazy="dynamic")