Node.js- scan DynamoDB AWS- adding parameters

Question

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"
}

Mark B · Accepted Answer · 2016-06-22 01:00:47Z

1

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};

edited Jun 22, 2016 at 1:00

answered Jun 22, 2016 at 0:33

Mark B

203k27 gold badges339 silver badges332 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Grzegorz Brzęczyszczykiewicz Over a year ago

Now i get such an error: { [ValidationException: ExpressionAttributeValues contains invalid key: Syntax error; key: "high_lat"] message: 'ExpressionAttributeValues contains invalid key: Syntax error; key: "high_lat"',

Mark B Over a year ago

Ah sorry, I missed the syntax slightly. See my updated answer.

Grzegorz Brzęczyszczykiewicz Over a year ago

Better but now I get: [ValidationException: Invalid FilterExpression: An expression attribute value used in expression is not defined; attribute value: :higher_lat] message: 'Invalid FilterExpression: An expression attribute value used in expression is not defined; attribute value: :higher_lat',

Mark B Over a year ago

I assume the names like ":lower_lon" and ":higher_lat" aren't actual property names in your table. You need to add the mapping of each name in ExpressionAttributeNames. Add ":high_lat" = "high_lat", ":low_lat" = "low_lat", etc.

Grzegorz Brzęczyszczykiewicz Over a year ago

I don't even have such properties in my table. My table contains location latitude and longitude. low_lat, high_lat, etc are values (low latitude value, high latitude value) sent from android to find suitable items in DataBase and send them back to android app.

|

Collectives™ on Stack Overflow

Node.js- scan DynamoDB AWS- adding parameters

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related