MongoDB從嵌套文檔檢索選定對象

Question

是否可以查詢嵌套文檔中的特定對象？繼承人的一個例子，

Collection : Threads 
{ 
    Documents : Messages 
    { 
     threadId = 1 
     messages = [ 
      { 
       user = amy 
       date = 01/01/2012 
       content = hey 
      }, 
      { 
       user = bell 
       date = 01/01/2012 
       content = hey 
      }, 
      { 
       user = bell 
       date = 01/02/2012 
       content = whats up 
      } 
     ] 
    }, 
    { 
     threadId = 2 
     messages = [ 
      { 
       user = courtney 
       date = 01/03/2012 
       content = first! 
      } 
     ] 
    } 
} 

我想我的查詢說{ threadId : 1, 'messages.date' : { $gt : 01/01/2012 } }, { fields : { messages : 1 } }。但它會返回所有的文件信息，當我真的想要結果是這樣的時，

messages = [ 
    { 
     user = bell 
     date = 01/02/2012 
     content = whats up 
    } 
] 

Answer 1

You cannot return just the selected subdocument。你會得到他們全部。所以你必須在客戶端進行過濾。