更新 AWS dynamoDB 中的 JSON 数组 [英] updating a JSON array in AWS dynamoDB

问题描述

我的文档如下所示:

{
  "data": {
      "eventId": "20161029125458-df-d",
      "name": "first",
      "purpose": "test",
      "location": "yokohama",
      "dateArray": [],
      "attendees": [
        {
          "attendeeId": "2016102973634-df",
          "attendeeName": "lakshman",
          "personalizedDateSelection": {}
        },
        {
          "attendeeId": "2016102973634-tyyu",
          "attendeeName": "diwaakar",
          "personalizedDateSelection": {}
        }
      ]
    }
}

比如说，我需要用 attendeeId: 2016102973634-df 更新参加者 JSON 数组.我尝试了很多方法使用更新和条件表达式，但没有成功.

Say, I need to update the attendee JSON array with attendeeId: 2016102973634-df. I tried many ways ways using update and condition expression, but no success.

这是我的尝试:

const params = {
  TableName: "event",
  Key: {
    "eventId": eventId 
  },
  UpdateExpression: "SET attendees[???] = ",
  ConditionExpression: attendees.attendeeId = "2016102973634-df", 
  ExpressionAttributeValues: {
    ":attendee" : attendeeList
  },
  ReturnValues: "ALL_NEW"
};


dynamo.update(params, (err, data) => {
  if (err) {
    return reject(err);
  }
  console.log(data.Attributes);
});

找不到用于更新数组中的 Json 的任何资源.

Could not find any resources for updating an Json in a array.

@notionquest 发表评论后:- 没有使用任何 JsonMarshaller.最初我将空数组添加到参加者字段，如下所示:

After @notionquest's comment: - Have not used any JsonMarshaller. Initially I added the empty array to attendees field like this:

{
  "eventId": "20161029125458-df-d",
  "name": "first",
  "purpose": "test",
  "location": "yokohama",
  "dateArray": [],
  "attendees": []
}

然后当新的 attendee 出现时，我将其添加到 attendees 属性中，如下所示:

and then When a new attendee comes I add it to the attendees property like this:

const attendee = {
  "attendeeName": "user1",
  "personalizedDateSelection": {"today": "free"}
}
const attendeeList = [attendee];
const eventId = "20161029125458-df-d";


const params = {
  TableName: "event",
  Key: {
    "eventId": eventId
  },
  UpdateExpression: "SET attendees = list_append(attendees, :attendee)",
  ExpressionAttributeValues: {
    ":attendee" : attendeeList
  },
  ReturnValues: "ALL_NEW"
};


dynamo.update(params, (err, data) => {
  if (err) {
    return reject(err);
  }
  console.log("in update dynamo");
  console.log(data.Attributes);
});

正如您在上面的代码片段中看到的，最初我添加了空的 [] 数组，并使用上面的代码添加了一个新的与会者.现在，如何更新数组中的特定 JSON.如果你说这是不可能的，我还能尝试什么?

As you have seen in the above snippets, initially I add empty [] array and add a new attendee using the above code. Now, How do I update a specific JSON in an array. If you say that is not possible, what else can I try?

我应该试试这个:

1. 获取完整的 JSON.
2. 操作 JSOn 并在我的 nodeJS 中更改我想要的东西.
3. 然后将新的 JSON 更新为 dynamoDB.
4. 但这会消耗对 dynamoDB 的两次调用，这似乎是低效的.

想知道是否有任何圆形方式?

Would like to know If there is any round way ?

推荐答案

我找不到任何答案来查询和更新 JSON 数组.我认为这可能是 AWS 不允许这些功能的盈利动机.如果您需要查询除主键之外的特定ID，则需要制作具有成本效益的二级索引.此二级索引成本是 dyn 的额外成本amoDB 表开销.

I could not find any answer to query and update the JSON-array. I think this may be AWS profitable motive to not allow those features. If you need to query on a particular ID other than primary key, you need to make a secondary index which is cost effective. This secondary index cost is additional to the dyn amoDB table cost.

由于我不想为二级索引支付额外费用，因此我将 dynamoDB 架构更改为以下内容:

Since, I did not want to pay extra bucks on secondary index, I changed my dynamoDB schema to the following:

{
  "data": {
      "eventId": "20161029125458-df-d",
      "name": "first",
      "purpose": "test",
      "location": "yokohama",
      "dateArray": [],
      "attendees": {
        "2016102973634-df": {
          "attendeeId": "2016102973634-df",
          "attendeeName": "lakshman",
          "personalizedDateSelection": {}
        },
        "2016102973777-df": {
          "attendeeId": "2016102973777-df",
          "attendeeName": "ffff",
          "personalizedDateSelection": {}
        }
      }
    }
}

将与会者从 [] 更改为 {}.这让我可以灵活地查询特定的 attendeeId 并更改与之关联的整个 JSON.尽管这是一个多余的步骤，但我不想在我的爱好项目上花费额外的钱.

Changing attendees from [] to {}. This allows me the flexibility to query particular attendeeId and change the entire JSON associated with that. Even though, this is a redundant step, I do not want to spend extra bucks on my hobby project.

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