添加到SQLAlchemy的多对多关系

Question

前提条件：从预定列表中搜索项目实例的公共注释（字符串）。在单个评论中可以有多个列表匹配。

我正在尝试使用多对多结构来跟踪这一点。

我创建使用SQLAlchemy的（Python的3.5）

reddit_assoc = Table('reddit_assoc', Base.metadata, 
    Column('comment_id', Integer, ForeignKey('reddit_comments.comment_id')), 
    Column('character_id', Integer, ForeignKey('characters.character_id')) 
    ) 

class characters(Base): 
    __tablename__ ='characters' 

    character_id = Column(VARCHAR(20),primary_key=True) 
    name = Column(VARCHAR(3072)) 
    added = Column('added', DateTime, default=datetime.datetime.now()) 
    reddit_mentions = relationship('reddit_comments', secondary='reddit_assoc', back_populates='character_mentions') 

class reddit_comments(Base): 
    __tablename__ = 'reddit_comments' 
    comment_id = Column(VARCHAR(50), primary_key=True) 
    comment_author = Column(VARCHAR(300)) 
    comment_created = Column(VARCHAR(300)) 
    link_id = Column(VARCHAR(50)) 
    subreddit_id = Column(VARCHAR(50)) 
    character_mentions = relationship('characters', secondary='reddit_assoc', back_populates='reddit_comments') 

并使用下面找到匹配

def char_counter(comment): 
    Session = DBSession() 
    reader = Session.query(characters).all() 

    for char in reader: 
     if char[0] in comment['comment_body'] or char[1] in comment['comment_body']: 
      # We have a match. Add to database. 
      Session.merge(reddit_comments(#relevant information from comment#)) 
      #How do I add to the Many to Many here? 
      Session.commit() 
     Session.close() 

问题以下数据库结构：寻找在评论以上片段，我不明白我如何添加可能多个字符匹配的关系从通信ent ['comment_body']字符串正确地转换为reddit_assoc关联表。有人可以请进一步建议吗？

Answer 1

您在本例中使用的关系表现为列表。所以你需要添加新创建的reddit评论列表reddit_mentions。

def char_counter(comment): 
    Session = DBSession() 
    reader = Session.query(characters).all() 

    for char in reader: 
     if char[0] in comment['comment_body'] or char[1] in comment['comment_body']: 
      # We have a match. Add to database. 
      rc = reddit_comments(#relevant information from comment#) 
      Session.flush() # to ensure you have primary key, although may not be needed 
      char.reddit_mentions.append(rc) # this will eventually fill your reddit_assoc table 
      Session.add(char) 

    # move this outside of loop   
    Session.commit() 
    Session.close()