Error InvalidParameterType: Expected params.Item['pid'] to be a structure in DynamoDB

Question

Note: all these are happening on the local instance of DynamoDB.

This is the code that I've used to create a table from the DynamoDB Shell:

var params = {
    TableName: "TABLE-NAME",
    KeySchema: [
        { AttributeName: "pid", 
          KeyType: "HASH"
        }
    ],
    AttributeDefinitions: [
        { AttributeName: "pid",
          AttributeType: "S"
        }
    ],
    ProvisionedThroughput: {
        ReadCapacityUnits: 1,
        WriteCapacityUnits: 1
    }
};


dynamodb.createTable(params, function(err, data) {
    if (err)
        console.log(JSON.stringify(err, null, 2));
    else
        console.log(JSON.stringify(data, null, 2));
});

This is the function that is being called to add elements into the DB (in node.js):

function(request, response) {
  params = {
    TableName: 'TABLE-NAME',
    Item: {
      pid: 'abc123'
    }
  };
  console.log(params);
  dynamodb.putItem(params, function(err, data) {
    if (err)
      console.log(JSON.stringify(err, null, 2));
    else
      console.log(JSON.stringify(data, null, 2));
  });
}

The output that I get is:

{ TableName: 'TABLE-NAME',
  Item: { pid: 'abc123' } }   // THIS IS PARAMS
{
  "message": "There were 7 validation errors:\n* InvalidParameterType: Expected params.Item['pid'] to be a structure\n* UnexpectedParameter: Unexpected key '0' found in params.Item['pid']\n* UnexpectedParameter: Unexpected key '1' found in params.Item['pid']\n* UnexpectedParameter: Unexpected key '2' found in params.Item['pid']\n* UnexpectedParameter: Unexpected key '3' found in params.Item['pid']\n* UnexpectedParameter: Unexpected key '4' found in params.Item['pid']\n* UnexpectedParameter: Unexpected key '5' found in params.Item['pid']",
  "code": "MultipleValidationErrors",
  "errors": [
    {
      "message": "Expected params.Item['pid'] to be a structure",
      "code": "InvalidParameterType",
      "time": "2015-11-26T15:51:33.932Z"
    },
    {
      "message": "Unexpected key '0' found in params.Item['pid']",
      "code": "UnexpectedParameter",
      "time": "2015-11-26T15:51:33.933Z"
    },
    {
      "message": "Unexpected key '1' found in params.Item['pid']",
      "code": "UnexpectedParameter",
      "time": "2015-11-26T15:51:33.933Z"
    },
    {
      "message": "Unexpected key '2' found in params.Item['pid']",
      "code": "UnexpectedParameter",
      "time": "2015-11-26T15:51:33.933Z"
    },
    {
      "message": "Unexpected key '3' found in params.Item['pid']",
      "code": "UnexpectedParameter",
      "time": "2015-11-26T15:51:33.933Z"
    },
    {
      "message": "Unexpected key '4' found in params.Item['pid']",
      "code": "UnexpectedParameter",
      "time": "2015-11-26T15:51:33.934Z"
    },
    {
      "message": "Unexpected key '5' found in params.Item['pid']",
      "code": "UnexpectedParameter",
      "time": "2015-11-26T15:51:33.934Z"
    }
  ],
  "time": "2015-11-26T15:51:33.944Z"
}

I don't understand why or how it is getting keys 0, 1, 2, 3, 4 and 5 when they aren't present on being printed in the previous line.

Also, how do I fix the error Expected params.Item['pid'] to be a structure? I have declared it as a string and am trying to store a string!

Other notes: The same code that I've used in the function works just fine when I run it on the shell. I have also included the aws-sdk and have configured it as required:

var AWS = require('aws-sdk');
AWS.config.region = 'us-east-1';
AWS.config.endpoint = 'http://localhost:8000/'
var dynamodb = new AWS.DynamoDB();

Answer 1

The putItem() method on the AWS.DynamoDB class is expecting the params.Item object to be formatted as a AttributeValue representation. That means you would have to change this:

params = {
  TableName: 'TABLE-NAME',
  Item: {
    pid: 'abc123'
  }
};

Into this:

params = {
  TableName: 'TABLE-NAME',
  Item: {
    pid: {
      S: 'abc123'
    }
  }
};

---

If you want to use native javascript objects you should use the AWS.DynamoDB.DocumentClient class, that automatically marshals Javascript types onto DynamoDB AttributeValues like this:

• String -> S
• Number -> N
• Boolean -> BOOL
• null -> NULL
• Array -> L
• Object -> M
• Buffer, File, Blob, ArrayBuffer, DataView, and JavaScript typed arrays -> B

It provides a put() method, that delegates to AWS.DynamoDB.putItem().