Mongodb在子陣列內更新操作

Question

我對mongodb非常陌生，在更新操作中遇到了一些麻煩。下面是文檔：

{ 
    "username" : "amitverma", 
    "notifications" : { 
     "notification_add_friend" : [ 
      { 
       "sender" : "macbook", 
       "action" : "", 
       "type" : "", 
       "objectType" : "request", 
       "objectUrl" : "", 
       "isUnread" : true 
      }, 
      { 
       "sender" : "safari", 
       "action" : "", 
       "type" : "", 
       "objectType" : "request", 
       "objectUrl" : "", 
       "isUnread" : true 
      }, 
      { 
       "sender" : "chrome", 
       "action" : "", 
       "type" : "", 
       "objectType" : "request", 
       "objectUrl" : "", 
       "isUnread" : true 
      } 
     ] 
    }, 
    "_id" : ObjectId("526598c86f45240000000001") 
} 
{ 
    "username" : "macbook", 
    "notifications" : { 
     "notification_add_friend" : [ 
      { 
       "sender" : "amitverma", 
       "action" : "", 
       "type" : "", 
       "objectType" : "a_r", 
       "objectUrl" : "", 
       "isUnread" : true 
      } 
     ] 
    }, 
    "_id" : ObjectId("526598d06f45240000000002") 
} 

我想與{"sender":"safari"}內"username":"amitverma" 我曾嘗試$ elemMatch與$集刪除子陣列，但就是無法得到正確的查詢。

Answer 1

你不想在這裏使用$set，但$pull（see docs），而你能使用$elemMatch進一步指定查詢，你不需要。

下會拉所有{"sender": "safari"}從文檔的子陣列匹配{"username": "amitverma"}

db.yourcollection.update({"username": "amitverma"}, { 
    $pull: {"notifications.notifications_add_friend": {"sender": "safari"}} 
}) 

至於您的評論添加好友通知，如果您想更新您的特定元素會使用$set組合與$elemMatch和positional operator $。對於你的例子，如：

db.yourcollection.update({ 
    "username": "amitverma", 
    "notifications.notifications_add_friend": { 
    $elemMatch: {"sender": "safari"} 
    } 
}, { 
    $set: { 
    "notifications.notifications_add_friend.$.isUnread": false 
    } 
})