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

I thought I'd just throw this out there as another option for adding or appending an "object" to a list. It's a map being added an item to the list, and worked well for me:

var upsertExpr = (obj.comments == undefined) ? " :attrValue" : "list_append(#attrName, :attrValue)";

var params = {
    TableName: 'tableName',
    Key: {
        'id': {'S': id},
    },
    UpdateExpression : "SET #attrName = " + upsertExpr,
    ExpressionAttributeNames : {
      "#attrName" : "comments"
    },
    ExpressionAttributeValues : {
      ":attrValue" : {
            "L": [
                { "M" : 
                    {
                        "comment": {"S": comment},
                        "vote": {"N": vote.toString()}
                    }
                }
            ]
        }
    }
};