NTU SDI 4.3: Mongo DB aggregation pipelines with restaurants sample data

mongodb-aggregations.js

// region Setup database client

const { MongoClient } = require( 'mongodb' );

// Server to connect to
const uri = "mongodb://localhost:27017";

const dbServer = new MongoClient( uri );

// endregion Setup database client


// region Connect to the database and test querying
(async () => {
	await dbServer.connect();
	const db = dbServer.db( 'sample_restaurants' );
	const restaurants = db.collection( 'restaurants' );

	console.log( '\n-----------------------------------------------\n' );

	// region $match and $project demo
	const pipeline = [
		// $match address.zipcode => 10466, cuisine => Chinese
		{ $match: { "address.zipcode": "10466", "cuisine": "Chinese" } },

		// $project name to restaurant_name
		{ $project: { restaurant_name: '$name', _id: false } },

		{$limit: 10},
	];

	const restaurantDocs = await restaurants.aggregate( pipeline ).toArray();

	console.log( 'Chinese restaurants in 10466: \n', restaurantDocs );	
	// endregion $match and $project demo

	console.log( '\n-----------------------------------------------\n' );

	// region $group demo
	const groupPipeline = [
		// Find number of restaurants by cuisine
		{ $group: { _id: '$cuisine', noOfOccurences: { $count: {} } } },

		// Additional feature, order cuisines by popularity
		{ $sort: { noOfOccurences: -1 } },

		// Top five most popular cuisines in our database
		{$limit: 5}
	];

	const cousineCount = await restaurants.aggregate( groupPipeline ).toArray();

	console.log( 'Restaurant count by cuisine: \n', cousineCount );

	// endregion $group demo

	console.log( '\n-----------------------------------------------\n' );

	// region $sort demo
	
	// Get first 10 alphabetically arranged restaurants
	const first10Pipeline = [
		// Filter out empty name docs
		{ $match: { 'name': {$ne: ''} } },

		// Sort by name
		{ $sort: { 'name': 1 } },

		// Limit to 10 results
		{ $limit: 10 },

		// Project restaurants name
		{ $project: { 'restaurant_name': '$name', _id: 0 } }
	];

	const first10RestaurantDocs = await restaurants.aggregate( first10Pipeline ).toArray();

	console.log( 'First 10 sorted restaurants: \n', first10RestaurantDocs );

	// endregion $sort demo

})();
// endregion Connect to the database and test querying