Question

我无法通过Flask-SQLAlchemy查询ID。

我的模型如下：

class Network(Base):
    __tablename__ = 'NETWORKS'
    __table_args__ = {'schema':'METROLIVE'}

    id = db.Column(db.Integer, unique=True, primary_key=True, autoincrement=True)
    datestamp = db.Column(db.Date, default=dt.datetime.now())
    sensor_list = db.Column(db.PickleType)
    arc_trans = db.Column(db.PickleType)

    def __init__(self, datestamp, sensor_list, arc_trans):
        self.datestamp = datestamp
        self.sensor_list = sensor_list
        self.arc_trans = arc_trans

class Node(Base):
    __tablename__ = 'NODES'
    __table_args__ = {'schema':'METROLIVE'}

    id = db.Column(db.Integer, unique=True, primary_key=True, autoincrement=True)
    name = db.Column(db.Integer, unique=True, nullable=False)
    lat = db.Column(db.Float, nullable=False)
    long = db.Column(db.Float, nullable=False)
    x = db.Column(db.Float, nullable=False)
    y = db.Column(db.Float, nullable=False)


    def __init__(self, name, lat, long, x, y):
        self.name = name
        self.lat = lat
        self.long = long
        self.x = x
        self.y = y

class Arc(Base):
    __tablename__ = 'ARCS'
    __table_args__ = {'schema':'METROLIVE'}

    id = db.Column(db.Integer, unique=True, primary_key=True, autoincrement=True)
    network = db.Column(db.Integer, db.ForeignKey('METROLIVE.NETWORKS.id'))
    node_a = db.Column(db.Integer, db.ForeignKey('METROLIVE.NODES.id'))
    node_b = db.Column(db.Integer, db.ForeignKey('METROLIVE.NODES.id'))
    dx = db.Column(db.Float, nullable=False)
    dy = db.Column(db.Float, nullable=False)


    def __init__(self, network, node_a, node_b, dx, dy):
        self.network = network
        self.node_a = node_a
        self.node_b = node_b
        self.dx = dx
        self.dy = dy

我在将Network表中的对象插入时没有问题，

ins_network = Network(datestamp = dt.datetime.now(),
                            sensor_list = pickle.dumps(sensors),
                            arc_trans = pickle.dumps(arc_trans_ins))
    db.session.add(ins_network)
    db.session.commit()

当我尝试查询网络ID时，出现一个奇怪的错误。我尝试过：

test_id = Network.query.order_by(desc(Network.id)).first()
test_id = pickle.loads(Network.query.order_by(desc(Network.id)).first()

我尝试通过访问插入的对象ID（在本例中为ins_network.id）来检索插入的ID，但这没有用。

在所有情况下我收到的错误消息均写为：

Traceback (most recent call last):
  File "/~path/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
  File "/~path/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
  File "/~path/lib/python3.6/site-packages/flask_restplus/api.py", line 319, in wrapper
resp = resource(*args, **kwargs)
  File "/~path/lib/python3.6/site-packages/flask/views.py", line 88, in view
return self.dispatch_request(*args, **kwargs)
  File "/~path/lib/python3.6/site-packages/flask_restplus/resource.py", line 44, in dispatch_request
resp = meth(*args, **kwargs)
  File "/~path/app/api.py", line 37, in get
snp.nodes_to_arcs()
  File "/~path//app/network.py", line 106, in nodes_to_arcs
print("******* NETWORK ID = ", ins_network.id)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py", line 242, in __get__
return self.impl.get(instance_state(instance), dict_)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/attributes.py", line 594, in get
value = state._load_expired(state, passive)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/state.py", line 608, in _load_expired
self.manager.deferred_scalar_loader(self, toload)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 876, in load_scalar_attributes
only_load_props=attribute_names)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 188, in load_on_ident
identity_token=identity_token
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 250, in load_on_pk_identity
return q.one()
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2894, in one
ret = self.one_or_none()
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/query.py", line 2864, in one_or_none
ret = list(self)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 98, in instances
util.raise_from_cause(err)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 203, in raise_from_cause
reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 187, in reraise
raise value
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 79, in instances
rows = [proc(row) for row in fetch]
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 79, in <listcomp>
rows = [proc(row) for row in fetch]
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 511, in _instance
loaded_instance, populate_existing, populators)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/orm/loading.py", line 611, in _populate_full
dict_[key] = getter(row)
  File "/~path/lib/python3.6/site-packages/sqlalchemy/sql/sqltypes.py", line 1588, in process
return loads(value)
_pickle.UnpicklingError: invalid load key, '<'.

我不知道我在做什么错。即使我腌制ins_network对象中的某些对象，也不应该腌制整个对象，对吧？

test_id = Node.query.order_by(desc(Node.id)).first()是一种魅力。

P.S我正在使用DB2作为数据库。

提前谢谢！

使用Flask-SQLAlchemy查询时出现开箱错误

0 个答案: