CODEWITHSUNDEEP
node.jsamazon-web-servicesaws-lambda
Grzegorz Brzęczyszczykiewicz
Grzegorz Brzęczyszczykiewicz

Reputation: 1676

Node.js- scan DynamoDB AWS- adding parameters

I get data from dynamoDB with Lambda AWS. I try to add parameter to my parameters which I send to Lambda from android app:

if (typeof event.high_lat != "undefined") {
            params.ExpressionAttributeValues = event.high_lat;
        }

But I get an error:

 [InvalidParameterType: Expected params.ExpressionAttributeValues to be a map]
  message: 'Expected params.ExpressionAttributeValues to be a map',

Anyone know how to solve it?

My whole code:

var AWS = require('aws-sdk');
var db = new AWS.DynamoDB();

exports.handler = function(event, context) {


   var params = {
    TableName: "Events", //"StreamsLambdaTable",
    ProjectionExpression: "ID, description, endDate, imagePath, locationLat, locationLon, #nm, startDate, #tp, userLimit",  //specifies the attributes you want in the scan result.
    FilterExpression: "locationLon between :lower_lon and :higher_lon and locationLat between :lower_lat and :higher_lat",
    ExpressionAttributeNames: {
        "#nm": "name",
        "#tp": "type",
    },

     ExclusiveStartKey: {
       "ID": {"S": event.LastEvaluatedKey}
     },

    ExpressionAttributeValues: {
        ":lower_lon": {"N": event.low_lon},
        ":higher_lon": {"N": event.high_lon}, 
        ":lower_lat": {"N": event.low_lat}
    }
};


if (typeof event.high_lat != "undefined") {
            params.ExpressionAttributeValues = event.high_lat;
        }


  db.scan(params, function(err, data) {
    if (err) {
      console.log(err); // an error occurred
      } 
    else {
      data.Items.forEach(function(record) {
           console.log(
                record.name.S + "");
        });
        context.succeed(data.Items);


      }
  });
};

Example of code sent from android app:

{
  "low_lon": "16",
  "high_lon": "17",
  "low_lat": "52",
  "high_lat": "53"
}

Upvotes: 1

Views: 818

Answers (1)

Mark B
Mark B

Reputation: 200562

You are blowing away your entire ExpressionAttributeValues map with a single value. You just need to look at the code you wrote above to see how you should add values to the ExpressionAttributeValues map.

Change this:

params.ExpressionAttributeValues = event.high_lat;

To this:

params.ExpressionAttributeValues[":higher_lat"] = {"N": event.high_lat};

Upvotes: 1

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