postgresql - "Can' t adapt type"错误关于 SQLAlchemy/PostGreSQL 的外键属性

Question

我遇到了 PostGreSQL 8.4 和表反射的问题。我的元数据对象似乎没问题(它有外键、主键、每个列和表)。但是当我尝试通过外键将一个对象关联到另一个对象时，我得到:“sqlalchemy.exc.ProgrammingError: (ProgrammingError) can't adapt type 'EventParameters' 'INSERT INTO event (".

我正在使用 SQLAlchemy 0.6.3 (psycopg2 2.2.1) 和 PostGreSQL 8.4.5

在这里，我的代码:

#! /usr/bin/env python 

from sqlalchemy import MetaData, create_engine 
from sqlalchemy.orm import mapper, sessionmaker 

class EventParameters(object): 
    pass 

class Event(object): 
    pass 

engine = create_engine('postgresql://postgres:toto@127.0.0.1:5432/renass') 
metadata = MetaData() 
metadata.reflect(bind=engine) 
Session = sessionmaker(bind=engine) 
session = Session() 
mapper(EventParameters, metadata.tables['eventparameters']) 
mapper(Event, metadata.tables['event']) 

ep = EventParameters() 
ep.publicid = 'test' 

e = Event() 
e.publicid = 'test' 
e.eventparametersid=ep 

session.add(e) 
session.commit()

和我的数据库:

CREATE TABLE EventParameters ( 
    id SERIAL PRIMARY KEY, 
    publicID varchar(255) UNIQUE NOT NULL, 
    description varchar(255), 
    creationInfo_agencyID varchar(64), 
    creationInfo_agencyURI varchar(255), 
    creationInfo_author varchar(128), 
    creationInfo_authorURI varchar(255), 
    creationInfo_creationTime time, 
    creationInfo_version varchar(64) 
); 

CREATE TABLE Event ( 
    id SERIAL PRIMARY KEY, 
    eventParametersID integer NOT NULL REFERENCES EventParameters(id), 
    publicID varchar(255) UNIQUE NOT NULL, 
    preferredOriginID integer, 
    preferredMagnitudeID integer, 
    preferredFocalMechanismID integer, 
    type EventType, 
    typeCertainty EventTypeCertainty, 
    creationInfo_agencyID varchar(64), 
    creationInfo_agencyURI varchar(255), 
    creationInfo_author varchar(128), 
    creationInfo_authorURI varchar(255), 
    creationInfo_creationTime time, 
    creationInfo_version varchar(64) 
);

似乎 SQLAlchemy 没有将属性“eventparametersid”识别为关系......

提前谢谢你法比安

Answer 1

为了使您的代码正常工作，您应该更改 Event 类的映射器调用以包含两个类之间的映射

mapper(Event, metadata.tables['event'], properties={
    'eventparameters': relation(EventParameters)
})

然后使用该列来分配 EventParameters 实例

ep = EventParameters()
ep.publicid = 'test'

e = Event()
e.publicid = 'test'
e.eventparameters = ep