How to prevent creating a new item in UpdateItem if the item does not exist

Question

I am running an AWS Lambda service written in Node.js that interacts with a DynamoDB database. One of my methods performs an update (AWS.DynamoDB.DocumentClient().update) on

Answer 1

I bumped into a somehow similar problem using attribute_exists, the only difference is, I need to query from the table and get only the record that does have the attribute I need. Using ConditionExpression did not work for me. Thought of sharing it here in case someone is in need.

Here, if the subscriberKey is equal to given param and the attribute_exists (mobileNumber) within the record, it returns true, false otherwise.

var params = {
    TableName : table_name,
    IndexName: "subsciberKey-index",
    KeyConditionExpression: "subscriberKey = :subscriberKey",
    FilterExpression: "attribute_exists(mobileNumber)",
    ExpressionAttributeValues: {
        ":subscriberKey": subscriberNo
    }
};