Trouble making a Query of DynamoDB with Lambda (Node.js)

Question

I want to make a query to return all entries with a certain userID, in this case Will666. I have a primaryKey and a sortKey.

const AWS = require('aws-sdk');
const dynamodb = new AWS.DynamoDB({region: 'eu-west-2', apiVersion: '2012-08-10'});

exports.handler =  (event, context, callback) => {


    const params = {

        TableName: "signalepisodes",
        KeyConditionExpression: "userID = :a",
        ExpressionAttributeValues: {
        ":a": "Will666"
    }

    };
    dynamodb.query(params, function(err, data){
          if (err) {
            console.log(err);
            callback(err);
        } else {
            console.log(data);
              const items = data.Items.map(
                (dataField) => {
                  return { userID: dataField.userID.S, uploadDate: dataField.uploadDate.N, epTitle: dataField.epTitle.S };
              } 

                );

            callback(null, items);

        }
    });
    };

i get this error message when i test it. I guess my syntax is wrong but i can't work it out.

"errorType": "MultipleValidationErrors",

my dynamoDB table looks like this:

jarmod · Accepted Answer · 2020-03-28 17:16:24Z

The DynamoDB SDK has two types of client:

low-level client: new AWS.DynamoDB(...)
high-level client: new AWS.DynamoDB.DocumentClient(...)

You are currently using #1, but you are supplying attributes to your query as if you were using the document client #2.

So, either switch to the DocumentClient, and continue to use:

{":a": "Will666"}

Or stick with the low-level client and change your attributes to indicate value types, for example:

{":a": {"S": "Will666"}}

I'd recommend the DocumentClient because it significantly simplifies the marshalling and unmarshalling of data.

I would also recommend updating your code from the old callback style asynchronous code to the newer Promise-based options. For example, something like this:

exports.handler = async (event, context) => {
    const params = {
        TableName: "signalepisodes",
        KeyConditionExpression: "userID = :a",
        ExpressionAttributeValues: { ":a": "Will666" }
    };

    const items = await dynamodb.query(params).promise();

    for (const item of items) {
        console.log('Item:', item);
    }

    return items;
}

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