Trouble making a Query of DynamoDB with Lambda (Node.js) - amazon-web-services

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:

Answer 1

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;
}