在AWS dynamoDB中更新一个JSON数组。

My document looks like this:

我的文件是这样的:

{
  "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": {}
        }
      ]
    }
}

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.

例如，我需要用attendeeId: 2016102973634-df更新attendee JSON数组。我尝试了许多使用update和condition expression的方法，但是没有成功。

Here is my try:

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);
});

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

无法找到任何用于更新数组中的Json的资源。

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

@notionquest的评论:-没有使用任何JsonMarshaller。最初，我将空数组添加到参与者字段，如下所示:

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

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

然后当一个新的出席者到来时，我将它添加到参与者属性如下:

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);
});

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?

正如您在上面的代码片段中看到的，最初我添加了空[]数组，并使用上面的代码添加一个新的参与者。现在，如何在数组中更新特定的JSON。如果你说那是不可能的，我还能尝试什么?

Should I try this :

我应该试试这个吗?

Get the Full JSON.
得到完整的JSON。
Manipulate the JSOn and change the things I want in my nodeJS.
操作JSOn并更改nodeJS中需要的内容。
And then update the new JSON to dynamoDB.
然后将新的JSON更新到dynamoDB。
But this consumes two calls to dynamoDB which seems to be inefficient.
但是这消耗了对dynamoDB的两次调用，这似乎是低效的。

Would like to know If there is any round way ?

想知道是否有圆的路?

2 个解决方案

#1

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.

我找不到任何查询和更新json数组的答案。我认为这可能是AWS不允许这些功能的盈利动机。如果需要查询除主键之外的特定ID，则需要创建一个具有成本效益的辅助索引。这个次要的索引成本是dyn amoDB表成本的附加部分。

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

因为，我不想在二级索引上多花些钱，所以我将我的dynamoDB模式改为如下:

{
  "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": {}
        }
      }
    }
}

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.

改变参会者从[]到{}。这允许我查询特定的attendeeId并更改与之关联的整个JSON。尽管如此，这是一个多余的步骤，我不想花额外的钱在我的兴趣项目上。

#2

you can store the index of list. while updating the list we can use them. For example ,

可以存储列表的索引。在更新列表时，我们可以使用它们。例如,

{


"data": {
      "eventId": "20161029125458-df-d",
      "name": "first",
      "purpose": "test",
      "location": "yokohama",
      "dateArray": [],
      "attendees": [
        {  
          "index":0,  
          "attendeeId": "2016102973634-df",
          "attendeeName": "lakshman",
          "personalizedDateSelection": {}
        },
        {
           "index":1,
          "attendeeId": "2016102973634-tyyu",
          "attendeeName": "diwaakar",
          "personalizedDateSelection": {}
        }
      ]
    }
}
const params = {
  TableName: "event",
  Key: {
    "eventId": eventId 
  },
  UpdateExpression: "SET attendees[attendee.index].attendeeName = :value",
  ExpressionAttributeValues: {
    ":value" : {"S":"karthik"}
  },
  ReturnValues: "ALL_NEW"
};


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

#1