Python 无法正确保持多对多关系
Python 无法正确保持多对多关系,python,sqlalchemy,Python,Sqlalchemy,Article和Image具有多对多关系,它们的中间表是ArticleImage。我希望在Article表中看到1行,在Image表中看到3行,在ArticleImage表中看到3行Article和ArticleImage部件按预期工作,但是,Image表中有0行,ArticleImage表中的外键列“Image\u id”为“NULL”。要正确保存Image表中的行,我缺少什么? (没有打印错误) 我的代码: db_session = some_function() # get connec
Article
和Image
具有多对多关系,它们的中间表是ArticleImage
。我希望在Article
表中看到1行,在Image
表中看到3行,在ArticleImage
表中看到3行Article
和ArticleImage
部件按预期工作,但是,Image
表中有0行,ArticleImage
表中的外键列“Image\u id”为“NULL”。要正确保存Image
表中的行,我缺少什么?
(没有打印错误)
我的代码:
db_session = some_function() # get connection to database here
try:
article = Article()
db_session.add(article)
article.name = 'new post #1'
article.author = 'pojan'
article.images.append(Image('img1.jpg'))
article.images.append(Image('img2.jpg'))
article.images.append(Image('img3.jpg'))
db_session.merge(article)
db_session.commit()
print db_session.query(Article).count() # 1
print db_session.query(ArticleImage).count() # 3
print db_session.query(Image).count() # 0 <- error here, images are not added
except Exception as e:
print e
我的模型:
class Image(EntityClass):
attributes = ['id', 'name', 'path']
id = Column(Integer, primary_key=True)
name = Column(String(255), nullable=False)
path = Column(String(255), nullable=False, unique=True)
def __init__(self, name):
self.name = name
self.path = '/root/' + name
class ArticleImage(EntityClass):
article_id = Column(Integer, ForeignKey('article.id'))
image_id = Column(Integer, ForeignKey('image.id'))
image = relationship(Image)
position = Column(Integer)
class Article(EntityClass):
attributes = ['id','name','author']
id = Column(Integer, primary_key=True)
_images = relationship(ArticleImage,
order_by=[ArticleImage.position],
collection_class=ordering_list('position'))
images = association_proxy('_images', 'image')
name = Column(String(255), nullable=False)
author = Column(String(255), nullable=False)
(该设计基于我在互联网上找到的一个,我做了一些小改动)与您给出的示例相比,您在
article image
中遗漏了主键
我会得到
sqlalchemy.exc.ArgumentError:映射器映射器| ArticleImage | ArticleU image无法为映射表“article_image”组装任何主键列
使用您的ArticleImage
代码。根据您参考的,您还应该在ArticleImage
中添加一个构造函数,以便在创建ArticleImage
项目时将ArticleImage
与Image
关联,否则,ArticleImage
将永远不知道它应该引用哪个图像行
class ArticleImage(EntityClass):
article_id = Column(Integer, ForeignKey('article.id'))
image_id = Column(Integer, ForeignKey('image.id'))
image = relationship(Image)
position = Column(Integer)
def __init__(self, image=None):
self.image = image
class ArticleImage(EntityClass):
article_id = Column(Integer, ForeignKey('article.id'))
image_id = Column(Integer, ForeignKey('image.id'))
image = relationship(Image)
position = Column(Integer)
def __init__(self, image=None):
self.image = image