檢查多個ORM關係的字段是否包含值

Question

請求（我正在搜索的對象）由用戶分配的角色（由所述請求表示）組成。請看下圖：

class Request(db.Model): 
    __tablename__ = 'requests' 
    id = Column(Integer, primary_key=True) 
    user = Column(Integer, ForeignKey("users.id"), nullable=False) 
    role = Column(Integer, ForeignKey("roles.id"), nullable=False) 
    ... 

而且我們的關係：

# Define relationship between a User and their Requests 
requests = relationship('Request', backref='requested_by', lazy='dynamic') 

# Define relationship between a Role and Requests for this Role 
requests = relationship('Request', backref='requested_role', lazy='dynamic') 

最後，我們的目標：

# Return any requests made by a user or a role matching the search query 
data = Request.query.filter(or_(Request.requested_by.name.contains(search_query), 
           Request.requested_by.username.contains(search_query), 
           Request.requested_role.name.contains(search_query))).all() 

運行上面的代碼，結果如下：

AttributeError: Neither 'InstrumentedAttribute' object nor 'Comparator' object associated with Request.requested_by has an attribute 'name' 

這裏的想法是能夠根據用戶的相關細節或與其相關聯的角色查找請求對象。這可能嗎？

Answer 1

是的。你需要做一個連接：

Request.query.join(Request.requested_by) \ 
      .join(Request.requested_role) \ 
      .filter(or_(User.name.contains(search_query), 
         User.username.contains(search_query), 
         Role.name.contains(search_query))) 

注意，這會產生LIKE '%whatever%'查詢，如果你有一個大表，是令人難以置信的低效率。