Dynamodb - 更新对象数组中JSON对象的值

Question

Below is a sample item object/record stored in DynamoDb. I use NodeJS and AWS.DynamoDB.DocumentClient to access the database.

I'm building out a PUT function to update the status for an JSON object in an array. The function will have access to the Item's uuid and room's uuid . How can I simply (creatively) update the value of corresponding status field, given the array of JSON objects?

Params:

let params = {
  TableName: room-table,
  Key: {
    uuid: event.body.uuid
  },
  UpdateExpression : "??",
  ExpressionAttributeNames: {
      "??":"??"
  },
  ExpressionAttributeValues:{
    "??":"??"
  },
  ReturnValues:"ALL_NEW"
};

Item Object:

{
  "Item": {
    "uuid": "77b1e88e-5e60-44d9-b6ca-aec345c0dc99",
    "rooms": [
      {
        "room": "303",
        "status": "pending",
        "uuid": "b8f1c1a8-04a9-4c2e-82ad-bc3e81face35"
      },
      {
        "room": "302",
        "status": "pending",
        "uuid": "42fdc61a-4a25-4316-90c9-60209875d208"
      },
      {
        "room": "678",
        "status": "pending",
        "uuid": "7bedc115-20ed-4c3e-9cd7-7fed0520f4df"
      }
    ],
    "status": "pending"
  }
}

Answer 1

It's not possible to do this with ExpressionAttributeValues . I had to build a function to modify the object, similar to below:

function setStatus(jsonObj, uuid, newStatus) {
  for (var i=0; i<jsonObj.length; i++) {
    if (jsonObj[i].uuid === uuid) {
      jsonObj[i].status = newStatus;
      return jsonObj;
    }
  }
}

Answer 2

let params = {
  TableName: room-table,
  Key: {
    uuid: event.body.uuid
  },
  UpdateExpression : "SET #stat = :stat",
  ExpressionAttributeNames: {
      "#stat": "status"
  },
  ExpressionAttributeValues:{
    ":stat": "updatedStatusValue"
  },
  ReturnValues:"ALL_NEW"
};

ExpressionAttributeNames is needed because status is a DynamoDB reserved word . More info on Attribute Name and Attribute Value placeholders is available in the DynamoDB docs .