Dynamodb - Update value of JSON object in array of objects

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"
  }
}

It's not possible in a single update request because Dynamo will not be able to "find" the correct index in the Item.rooms array for you. The only way to make it possible would be for you to change Item.rooms from an array to an object where each key is a room's uuid. Then you could use an update expression of something like SET rooms.#roomUUID.status = :roomStatus. — idbehold
– idbehold, Commented Dec 6, 2016 at 16:07
Ok, can you submit that as your answer? Seems I'll need to use underscore jsto help me. — user1322092
– user1322092, Commented Dec 6, 2016 at 23:47

user1322092 · Accepted Answer · 2016-12-08 01:44:42Z

3

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;
    }
  }
}

answered Dec 8, 2016 at 1:44

user1322092

4,3207 gold badges40 silver badges56 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Peter Fennema · Accepted Answer · 2016-12-06 07:40:08Z

-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.

answered Dec 6, 2016 at 7:40

Peter Fennema

1,71012 silver badges14 bronze badges

2 Comments

Peter Fennema Over a year ago

Just noticed that your question is about updating an entire array. My answer is about 1 element....

user1322092 Over a year ago

Hi Peter, my goal is to update a single object in the array, not the same field in all array objects.

Collectives™ on Stack Overflow

Dynamodb - Update value of JSON object in array of objects

2 Answers 2

Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related