On Thu, Apr 25, 2019 at 8:34 AM Jan Sakalos <sakal...@gmail.com> wrote:
>
> Hello,
>
> I have to association proxies in code one is working and other not. I went
> through it many times and wasnt able to identify issue.
> Also please can you give me advice how to debug such issues if there is any?
The error is that a backref is not being located, which normally has
nothing to do with the association proxies. However it's not clear
if the association proxies are getting in the way of the
relationships.
The first step would be to run your operation without using the
association proxies, that is, create the Server2Patch object manually
and append it as though the association proxies weren't there.
Unfortunately I can't visually see how the error would occur which
means it is quite possible that some very unlikely interaction is
going on that can't be easily guessed, so I'll have to run it.
>
> Thanks
> Jano
>
> code:
>
>
> from sqlalchemy import Column, Integer, String, ForeignKey, DateTime, Time,
> ForeignKeyConstraint, and_, create_engine
> from sqlalchemy.ext.associationproxy import association_proxy
> from sqlalchemy.ext.declarative import declared_attr, declarative_base
> from sqlalchemy.orm import relationship, backref, sessionmaker
>
> engine_qualys =
> create_engine('mysql+pymysql://qualys:123456@localhost/sqlalchemy_test')
> Base = declarative_base()
> Base.metadata.create_all(engine_qualys)
>
>
> Session = sessionmaker(bind=engine_qualys)
>
>
> class BaseMixin():
>
> @declared_attr
> def __tablename__(cls):
> return cls.__name__.lower()
>
> def __repr__(self):
> values = ', '.join("%s=%r" % (n, getattr(self, n)) for n in
> self.__table__.c.keys())
> return "%s(%s)" % (self.__class__.__name__, values)
>
>
> class Request(BaseMixin, Base):
> id = Column(Integer, primary_key=True)
> ip = Column(String(30))
>
> #working
> servers = association_proxy('request_servers', 'server', creator=lambda
> server: Request2Server(server=server))
>
>
> class Server(BaseMixin, Base):
> ip = Column(String(30), primary_key=True, autoincrement=False)
>
>
> class Request2Server(BaseMixin, Base):
> request_id_fk = Column(Integer, ForeignKey('request.id'),
> primary_key=True)
> server_ip_fk = Column(String(30), ForeignKey('server.ip'),
> primary_key=True)
> data = Column(String(30))
>
> request = relationship('Request', backref=backref('request_servers'))
> server = relationship('Server', backref=backref('server_requests'))
>
> #not working
> patches = association_proxy('patches', 'patch', creator=lambda p:
> Server2Patch(patch=p))
>
>
> class Patch(BaseMixin, Base):
> qid = Column(Integer, primary_key=True)
>
>
> class Server2Patch(BaseMixin, Base):
> request2server_request_id_fk = Column(Integer,
> ForeignKey('request2server.request_id_fk'), primary_key=True)
> request2server_server_ip_fk = Column(String(30),
> ForeignKey('request2server.server_ip_fk'), primary_key=True)
> patch_qid_fk = Column(Integer, ForeignKey('patch.qid'), primary_key=True)
>
> request_server = relationship('Request2Server',
> backref=backref('patches'), foreign_keys=[request2server_request_id_fk,
> request2server_server_ip_fk])
> patch = relationship('Patch', backref=backref('request_servers2patch'),
> foreign_keys=[patch_qid_fk])
>
> __table_args__ = (ForeignKeyConstraint([request2server_request_id_fk,
> request2server_server_ip_fk],
> [Request2Server.request_id_fk,
> Request2Server.server_ip_fk]),
> {})
>
>
> Base.metadata.create_all(engine_qualys)
>
> s = Session()
>
> #generating some data
> request1 = Request(scan_title='tttt', ip='1.1.1.1,2.2.2.2')
> server1 = Server(ip='1.1.1.1')
> server2 = Server(ip='2.2.2.2')
> request1.servers.append(server1)
> request1.servers.append(server2)
> request1_server1 = request1.request_servers[0]
> patch1 = Patch(qid=1)
> s.add_all([request1, server1, server2, patch1])
> s.commit()
>
> #this is not working
> request1_server1.patches.append(patch1):
>
> Traceback (most recent call last):
> File "<input>", line 1, in <module>
> File
> "/home/saki/PycharmProjects/sqlalchemy_test/venv/lib64/python3.7/site-packages/sqlalchemy/orm/collections.py",
> line 1113, in append
> item = __set(self, item, _sa_initiator)
> File
> "/home/saki/PycharmProjects/sqlalchemy_test/venv/lib64/python3.7/site-packages/sqlalchemy/orm/collections.py",
> line 1078, in __set
> item = executor.fire_append_event(item, _sa_initiator)
> File
> "/home/saki/PycharmProjects/sqlalchemy_test/venv/lib64/python3.7/site-packages/sqlalchemy/orm/collections.py",
> line 715, in fire_append_event
> self.owner_state, self.owner_state.dict, item, initiator
> File
> "/home/saki/PycharmProjects/sqlalchemy_test/venv/lib64/python3.7/site-packages/sqlalchemy/orm/attributes.py",
> line 1134, in fire_append_event
> value = fn(state, value, initiator or self._append_token)
> File
> "/home/saki/PycharmProjects/sqlalchemy_test/venv/lib64/python3.7/site-packages/sqlalchemy/orm/attributes.py",
> line 1444, in emit_backref_from_collection_append_event
> child_impl = child_state.manager[key].impl
> KeyError: 'request_server'
>
>
> --
> 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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