How to use begins_with in AWS DynamoDb js sdk?

Question

I have a use case to apply begins_with on the primary sort key of an AWS Dynamodb table,
I am able to query the table using begins_with key condition from the AWS Console,
I wish to achieve the same using the AWS Javascript SDK.

I have the following fields in my table -
1. user_id (Primary partition key)
2. user_relation (Primary sort key)

I tried the following code -

let AWS = require('aws-sdk');
let util = require('util');

AWS.config.update({
    region: 'us-east-1'
});

let connection = new AWS.DynamoDB.DocumentClient();

let params = {
    TableName: 'user_details',
    KeyConditionExpression: 'user_id = :user_id and user_relation begins_with :user_relation',
    ExpressionAttributeValues: {
        ':user_id': "1234",
        ':user_relation': "followed-by"
    }
};

console.log('getQuery Params => ', params);
let dynamoDb = util.promisify(connection.query).bind(connection);
let results = await dynamoDb(params);
console.log('results => ', results);

I am getting a syntax error, what is the correct way to use begins_with while querying an AWS DynamoDb table?

Error -

(node:40474) UnhandledPromiseRejectionWarning: ValidationException: Invalid KeyConditionExpression: Syntax error; token: "begins_with", near: "user_relation BE
GINS_WITH :user_relation"

References -
https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB/DocumentClient.html#query-property

DynamoDB,how to query with BEGINS_WITH

Can't Query DynamoDB with Begins_with for list of Items

Where are you getting the Syntax error, can you post the error as well? — uday8486
– uday8486, Commented Dec 5, 2019 at 10:30
user_id = :user_id and begins_with(user_relation, :user_relation) — hoangdv
– hoangdv, Commented Dec 5, 2019 at 10:55

uday8486 · Accepted Answer · 2019-12-05 10:51:56Z

36

Try :

const params = {
  TableName: 'user_details',
  KeyConditionExpression: '#user_id = :user_id and begins_with(#user_relation, :user_relation)',
  ExpressionAttributeNames:{
    "#user_id": "user_id",
    "#user_relation": 'user_relation'
  },
  ExpressionAttributeValues: {
    ":user_id": "1234",
    ":user_relation": "followed-by"
  }
}

edited Dec 5, 2019 at 10:51

answered Dec 5, 2019 at 10:36

uday8486

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3 Comments

Dev1ce Over a year ago

getting (node:40537) UnhandledPromiseRejectionWarning: ValidationException: Invalid KeyConditionExpression: Syntax error; token: "begins_with", near: "#user_relation b egins_with :user_relation"

uday8486 Over a year ago

Updated the answer, tested it. It works. begins_with is a function, called like begins_with(#user_relation, :user_relation)

Costa Michailidis Over a year ago

Wondering why we need all these extra properties. All of that information fits inside KeyConditionExpress, can we not put it all there? ExpressionAttributeNames, and ExpressionAttributeValues are just name fluff. This could be so much simpler : (

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