DynamoDB Query Examples in Javascript

aws-dynamodb-query-examples.js

const AWS = require('aws-sdk');
const moment = require('moment');

const docClient = new AWS.DynamoDB.DocumentClient({
    region: process.env.AWS_REGION,
});

// Query where we have used a Reserved Word as the Partition Key
async function getCollectionList(collection) {
    /**
     * Get a list of items in a collection
     * @param {string} collection
     * @returns {object[]}
     */
    try {
        const params = {
            TableName: 'myTable',
            KeyConditionExpression: '#c = :c',
            ExpressionAttributeValues: {
                ':c': collection,
            },
            // ExpressionAttributeNames is required because we have used a reserved word "Collection"
            ExpressionAttributeNames: {
                '#c': 'Collection',
            },
        };
        const response = await docClient.query(params).promise();
        return response.Items;
    } catch (err) {
        throw err;
    }
}

// Query using an index with Partition Key "AssetId" and a date range in a Sort key "LogTime" (an ISO8601 string)
// We are also filtering for an 'ENABLED' AssetStatus
async function getAssetLogs(assetId) {
    /**
     * Get a list of items from the last 24hrs
     * @param {string} assetId
     * @returns {object[]}
     */
    try {
        const now = moment().toISOString();
        const start = moment().subtract(hours, '24').toISOString();
        const params = {
            TableName: 'myTable',
            IndexName: 'assetIdx',
            KeyConditionExpression: 'AssetId = :s and LogTime between :y and :n',
            FilterExpression = 'AssetStatus = :s', // Applied after the KeyConditionExpression
            ExpressionAttributeValues: {
                ':n': now,
                ':y': start,
                ':id': assetId,
                ':s': 'ENABLED'
            },
            ScanIndexForward: false, // Descending
        };
        const response = await docClient.query(params).promise();
        return response.Items;
    } catch (err) {
        throw err;
    }
}