CODEWITHSUNDEEP
pythondatabaseflasksqlalchemycascade
Marlyyy
Marlyyy

Reputation: 722

Flask - SQLAlchemy - clear tables as well as many-to-many linking table

I have two relations: Service and Stop. They form a many-to-many relationship with each other. I would like to clear all data from both tables while also emptying their many-to-many linking table.

I tried the following.

Service.query.delete()
Stop.query.delete()

This cleared both tables, however all data in the linking table remained untouched.

Service model:

class Service(Base):
    __tablename__ = 'service'
    id = Column(Integer, primary_key=True)
    name = Column(String(250), nullable=False)
    service_type = Column(String(250), nullable=False)
    description = Column(String(250), nullable=False)

Stop model:

class Stop(Base):
    __tablename__ = 'stop'
    id = Column(Integer, primary_key=True)
    name = Column(String(250), nullable=False)
    latitude = Column(Float(), nullable=False)
    longitude = Column(Float(), nullable=False)
    services = relationship("Service",
                    secondary=stop_service,
                    backref="stop")

Can someone please tell me how to automatically clear the linking table too, without having to loop through the "stop" table?

Upvotes: 2

Views: 491

Answers (1)

Sean Vieira
Sean Vieira

Reputation: 160015

Just set ondelete to CASCADE in your joining table (stop_service)'s definition:

stop_service = Table("stop_service", meta,
  Column("service_id", ForeignKey('Service.id', ondelete="CASCADE")),
  Column("stop_id", ForeignKey('Stop.id', ondelete="CASCADE")))

Upvotes: 2

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