SQLAlchemy的许多一对多的关系，如何过滤收集

Question

class Tag(Base): 
    __tablename__ = 'tags' 

    id = Column(Integer, primary_key=True, autoincrement=True) 
    slug = Column(String(50), unique=True, nullable=False) 


class Post(Base): 
    __tablename__ = 'posts' 

    id = Column(Integer, primary_key=True, autoincrement=True) 
    title = Column(String(200), unique=True, nullable=False) 
    tags = relationship('Tag', secondary=posts_tags, backref='posts') 
    created_time = Column(Date, default=date.today()) 
    content = Column(Text) 

，我可以按标签过滤的帖子：tag.posts，但我无法过滤的帖子收集使用表达式tag.posts.filter(Post.id > 10).all()如Django模型。

那么如何过滤多对多的集合呢？

Answer 1

my_tag = session.query(Tag).get(1) 

# option-1: if data is already loaded into memory 
posts = [post for post in my_tag.posts if post.id > 10] 

# option-2: query database with filter if you have "my_tag" instance 
posts = session.query(Post).with_parent(my_tag).filter(Post.id > 10).all() 

# option-3: query database with filter if you have slug value 
posts = session.query(Post).join(Tag, Post.tags).filter(Tag.slug == "my_slug").filter(Post.id > 10).all() 

Answer 2

还有一个外键和一个映射器。 http://docs.sqlalchemy.org/en/rel_0_9/orm/relationships.html#many-to-many