个人中心
gpt4 book ai didi

Comparing fields of 2 documents from same collection to produce a diff(比较来自同一集合的两个文档的字段以生成差异)

转载 作者：bug小助手 更新时间：2023-10-25 11:32:32 24 4
gpt4 key购买 nike



I have a system that
I wish to produce history of changes that happened to the documents in a collection at a particular timestamp

我有一个系统，我希望生成在特定时间戳对集合中的文档进行更改的历史


So let's say we have a document in a collection

因此，假设我们在集合中有一个文档


[
  {
    "property1" : "A",
    "property2" : "B",
    "createdAt" : "2023-05-18T06:36:00.000+00:00"
  }
]

which gets changed to:

它将更改为：


[
  {
    "property1" : "A1",
    "property2" : "B",
    "createdAt" : "2023-05-18T07:36:00.000+00:00"
  }
]

then for createdAt value "2023-05-18T07:36:00.000+00:00" I wish to produce output like

然后，对于createdAt值“2023-05-18T07：36：00.000+00：00”，我希望生成如下输出


[
  {
    "propertyChanged" : "property1",
    "oldValue": "A"
    "newValue": "A1"
  }
]

Still trying to figure the aggregate pipeline operators best for this

我仍在努力计算最适合这一点的聚合管道运算符


更多回答

Will the same document get updated or a new one will be inserted into the db?

是更新相同的文档还是将新的文档插入数据库？

Similar to @CharchitKapoor - how will you be getting the old document in order to compare with the new document? Will it be stored in another collection or are you doing a find then comparing that result with a proposed update?

类似于@ChArchitKapoor--为了与新文档进行比较，您将如何获取旧文档？它是否会存储在另一个集合中，或者您正在执行查找，然后将结果与建议的更新进行比较？

Hi @CharchitKapoor the new document would be inserted

Hi@ChArchitKapoor将插入新文档

Hi @jQueeny , The new document would be in the same collection . I wish to find what changed in 2 consecutive documents when sorted by createdat field.

Hi@jQueeny，新文档将位于同一集合中。我希望找出在按创建日期字段排序时，连续两个文档中发生了什么变化。

优秀答案推荐

How about something along these lines:

不如这样说吧：



  1. Use $match to filter the documents based on the timestamp


    db.collection.aggregate([
      {
        $match: {
          createdAt: "2023-05-18T07:36:00.000+00:00"             }
      },

       //2. Use lookup to perform a self-join on the collection to find the previous version of the document based on the createdAt field.
      {
        $lookup: {
          from: "collection",
          let: { createdAt: "$createdAt" },
          pipeline: [
            {
              $match: {
                $expr: {
                  $lt: ["$$createdAt", "$createdAt"]
                }
              }
            },
            { $sort: { createdAt: -1 } },
            { $limit: 1 }
          ],
          as: "previousVersion"
        }
      },
      //3. Use unwind to destructure the arrays from the last operation
      {
        $unwind: "$previousVersion"
      },

      //4. Finally you can use project to compare the fields
      {
         $project: {
           propertyChanged: {
             $setDifference: [
               { $objectToArray: { $arrayElemAt:      ["$previousVersion", 0] } },
               { $objectToArray: { $arrayElemAt: ["$$ROOT", 0]    } }
             ]
          }
       }
     },
     {
       $unwind: "$propertyChanged"
     },
     {
       $project: {
         propertyChanged: "$propertyChanged.k",
         oldValue: {
         $arrayElemAt: [
           { $objectToArray: { $ifNull: ["$previousVersion", {}]    } },
           { $indexOfArray: [ { $objectToArray: { $arrayElemAt: ["$previousVersion", 0] } }, "$propertyChanged.k" ] }
           ]
         },
         newValue: {
         $arrayElemAt: [
           { $objectToArray: { $ifNull: ["$$ROOT", {}] } },
           { $indexOfArray: [ { $objectToArray: { $arrayElemAt: ["$$ROOT", 0] } }, "$propertyChanged.k" ] }
           ]
        }
      }]);



更多回答

Hi @ChidiEkuma , Thanks for replying I tried this aggregate pipeline and this works fine till the last stage where we are projecting to get the output . In the last stage i'm getting following error $arrayElemAt's first argument must be an array, but is object

嗨@ChidiEkuma，感谢您的回复我尝试了这个聚合管道，这工作正常，直到最后一个阶段，我们预计得到的输出.在最后一个阶段，我得到以下错误$arrayElemAt的第一个参数必须是数组，但对象

@LakhanSINGH I've updated the solution Let me know if it resolves your errors

@LakhanSINGH我已经更新了解决方案，请告诉我它是否解决了您的错误

Hi @ChidiEkuma, so just before step number 4 where we are unwinding $previousVersion it turns previousVersion into an object now inthe first $project stage in step 4 , we cannot use it as an array in the following line { $objectToArray: { $arrayElemAt: ["$previousVersion", 0] } }, I'm getting the same error now at this line error: $arrayElemAt's first argument must be an array, but is object

Hi@chadiEkuma，就在我们展开$previousVersion的第4步之前，它将previousVersion转换为对象，现在处于第4步的第一个$project阶段，我们不能在以下行中将其用作数组：{$objectToArray：{$arrayElemAt：[“$previousVersion”，0]}}，现在我在此行收到相同的错误：$arrayElemAt的第一个参数必须是一个数组，但它是Object

@LakhanSINGH, I updated the original code but forgot to tag you.

@LakhanSINGH，我更新了原始代码，但忘了给你加标签。

24 4 0
文章推荐： flatten a singly linked list(扁平化单链表)
文章推荐： group mysql results by id for looping(按ID对MySQL结果进行分组以进行循环)
文章推荐： Connecting an HC05 bluetooth module to a Pololu A-Star 32U4 Prime SV microSD(将HC05蓝牙模块连接到Pololu A-Star 32U4 Prime SV microSD)
文章推荐： How to edit data in crud operations in django(如何在django中编辑crud操作中的数据)
bug小助手
个人简介

我是一名优秀的程序员,十分优秀！

作者热门文章
滴滴打车优惠券免费领取
滴滴打车优惠券
全站热门文章
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com