CODEWITHSUNDEEP
node.jsamazon-web-servicesamazon-dynamodbaws-sdk
Abdul Manaf
Abdul Manaf

Reputation: 5003

get min and max value from dynamoDb using node.js sdk

i used amazon dynamoDb for storing my data. i created database like this

Partition key : userid , Type : String

Sort key : score , Type : Number

and i inserted some rows.

manaf1 | 100

manaf2 | 500

manaf1 | 200

manaf1 | 600

i need to get max & min score for selected user. This is my code

var AWS = require("aws-sdk");

AWS.config.update({
    region: "myRegion"
});

var docClient = new AWS.DynamoDB.DocumentClient();

var params = {
    "TableName": "tableName",
    "KeyConditionExpression": "#userid = :userid ",
    "ExpressionAttributeNames": {
        "#userid": "userid"
    },
    "ExpressionAttributeValues": {
        ":userid": {
            "S": "manaf1"
        }
    }
};

docClient.query(params, function (err, data) {
    if (err) {
        console.error("Unable to query. Error:", JSON.stringify(err, null, 2));
    } else {
        console.log("Query succeeded.");
    }
});

But i got error when running this code.

Unable to query. Error: {
  "message": "One or more parameter values were invalid: Condition parameter type does not match schema type",
  "code": "ValidationException",
  "time": "2016-08-31T06:12:13.825Z",
  "requestId": "S1DFFJNDNVV4KQNSO5AEDASFMVJF66Q9ASHDFUAAJG",
  "statusCode": 400,
  "retryable": false,
  "retryDelay": 0
}

i need output like

manaf1 minimum score = 100

manaf1 maximum score = 600

  1. is it possible to get max or min of a number field from dynamoDb?
  2. what is the issue related with this code?

Upvotes: 4

Views: 10291

Answers (1)

notionquest
notionquest

Reputation: 39206

Please change the ExpressionAttributeValues as mentioned below. This should resolve the error.

ExpressionAttributeValues : {
        ':userid' : 'manaf1'        
    }

To sort the score in descending order, you can set the ScanIndexForward to false.

var params = {
    TableName : table,
    KeyConditionExpression : 'userid = :userid',
    ExpressionAttributeValues : {
        ':userid' : 'manaf1'        
    },
    ScanIndexForward: false
};

If ScanIndexForward is true, DynamoDB returns the results in the order in which they are stored (by sort key value). This is the default behavior. If ScanIndexForward is false, DynamoDB reads the results in reverse order by sort key value, and then returns the results to the client.

Type: Boolean

To sort the score in ascending order, you can set the ScanIndexForward to true.

Using ScanIndexForward you can get the MIN and MAX score record as first record in the result.

Upvotes: 6

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