DynamoDB : SET list_append not working using aws sdk

Question

I need to append a string to a string set in a dynamodb table using the corresponding key. This is the Update expression I use to do updateItem :

  var param         


        

Answer 1

maybe this will help someone. i was struggling with updating a list and was getting the same error message as the original poster. i managed to solve my problem when i finally understood the documentation (see the Adding Elements To a List example here http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.UpdateExpressions.html#Expressions.UpdateExpressions.ADD)

points to note are: 1) that the "list_append takes two lists as input, and appends the second list to the first." and 2) that ExpressionAttributeValues is a list! like this:

{
":vals": {
    "L": [
        { "S": "Screwdriver" },
        {"S": "Hacksaw" }
    ]
}

}

good luck!