Mongoose 查询帮助：对嵌套数组进行分页、排序、限制

Posted 2023-03-07

【中文标题】Mongoose 查询帮助：对嵌套数组进行分页、排序、限制

【英文标题】：Mongoose Query Help: Paginate, Sort, Limit on Nested Array

【发布时间】：2016-09-23 00:56:09

【问题描述】：

我有一个聊天猫鼬模型，下面是示例数据。如果这仍然不清楚，请回复我您的问题。非常感谢任何帮助。

         
            "_id" : ObjectId("5745910831a1sd58d070a8faa"), 
            "messages" : [
                
                    "user" : "user1", 
                    "message" : "How are you user1?", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:36:00.468+0000"), 
                    "_id" : ObjectId("5745912c31a1c58d070a904d")
                , 
                
                    "user" : "user1", 
                    "message" : "Hello user1", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:38:53.893+0000"), 
                    "_id" : ObjectId("5745912531a1c58d070a902e")
                
            ], 
            "createDate" : ISODate("2016-05-25T11:35:20.534+0000"), 
            "users" : [
                "57450b4506561ff5052f0a66", 
                "57450d8108d8d22c06cf138f"
            ], 
            "__v" : NumberInt(0)
        ,
         
            "_id" : ObjectId("57458e9331a1c58d070a8e30"), 
            "messages" : [
                
                    "user" : "user2", 
                    "message" : "How are you user2", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:46:03.240+0000"), 
                    "_id" : ObjectId("574590f331a1c58d070a8ede")
                , 
                
                    "user" : "user2", 
                    "message" : "Hello user2", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:48:53.925+0000"), 
                    "_id" : ObjectId("574590e931a1c58d070a8eab")
                
            ], 
            "createDate" : ISODate("2016-05-25T11:35:20.534+0000"), 
            "users" : [
                "5745149e3aaab38706c00b64", 
                "57450d8108d8d22c06cf138f"
            ], 
            "__v" : NumberInt(0)
        
         
            "_id" : ObjectId("5745910831a1c58d070a8faa"), 
            "messages" : [
                
                    "user" : "user3", 
                    "message" : "How are you user3?", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:56:00.468+0000"), 
                    "_id" : ObjectId("5745912c31a1c58d070a904d")
                , 
                
                    "user" : "user3", 
                    "message" : "Hello user3", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:58:53.893+0000"), 
                    "_id" : ObjectId("5745912531a1c58d070a902e")
                
            ], 
            "createDate" : ISODate("2016-05-25T11:35:20.534+0000"), 
            "users" : [
                "57450b4506561ff5052f0a66", 
                "57450d8108d8d22c06cf138f"
            ], 
            "__v" : NumberInt(0)
        ,
         
            "_id" : ObjectId("5745910831a1c58d070a8faa"), 
            "messages" : [
                
                    "user" : "user4", 
                    "message" : "How are you user4?", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:66:00.468+0000"), 
                    "_id" : ObjectId("5745912c31a1c58d070a904d")
                , 
                
                    "user" : "user4", 
                    "message" : "Hello user4", 
                    "readInd" : "N", 
                    "createDate" : ISODate("2016-05-25T11:68:53.893+0000"), 
                    "_id" : ObjectId("5745912531a1c58d070a902e")
                
            ], 
            "createDate" : ISODate("2016-05-25T11:35:20.534+0000"), 
            "users" : [
                "57450b4506561ff5052f0a66", 
                "57450d8108d8d22c06cf138f"
            ], 
            "__v" : NumberInt(0)
        

下面是解释：

user1分别在11:36和11:38发送了2条消息 user2分别在11:46和11:48发送了2条消息 user3 分别在 11:56 和 11:58 发送了 2 条消息 user4 分别在 11:66 和 11:68 发送了 2 条消息

我的预期结果是：

分页/限制条件：

每页显示 2 条记录。 仅显示基于用户的最新消息。

示例输出：

第 1 页：

   "user" : "57450d8108d8d22c06cf138f",              
   "message" : "How are you user4?"

   "user" : "57450d8108d8d22c06cf138f", 
   "message" : "How are you user3?"

第2页：

   "user" : "57450d8108d8d22c06cf138f", 
   "message" : "How are you user2"

   "user" : "57450d8108d8d22c06cf138f", 
   "message" : "How are you user1?"

【参考方案1】：

试试这种查询方式，对你有帮助

查询第一页

db.getCollection('message').aggregate( [  $match :  user : "57450d8108d8d22c06cf138f"  ,
 $unwind : "$messages"  ,
 $sort :  'messages.createDate' : -1 ,
  $limit : 2 ,
  $project :  _id: 0,'message':'$messages.message','user':'$messages.user'  ])

查询下一页

db.getCollection('message').aggregate( [  $match :  user : "57450d8108d8d22c06cf138f"  ,
     $unwind : "$messages"  ,
     $sort :  'messages.createDate' : -1 ,
      $limit : 2 , $skip : 2 
      $project :  _id: 0,'message':'$messages.message','user':'$messages.user'  ])

【讨论】：

感谢您的反馈。下一页的小改动。应该改变 $limit 和 $skip 的顺序，以便 $skip 排在第一位，$limit 排在第二位。 $skip:1, $limit:1

没错。我只是发布了答案，但我没有检查过

有人可以回答如何使用猫鼬做同样的事情吗？

@SyedSouban 我希望这个链接对你有帮助 excellencenodejsblog.com/… ，不需要在查询中改变任何东西，只需创建一个收集模型然后使用模型名称而不是把这个“db.getCollection(message )"