Sandeep Patel sandeep-cs-dev

Starting with MongoDB 4.2, you can use [aggregation pipelines to update documents][$pipelines]. Which leads to some really cool stuff.

For example, prior to this you could easily add sub-documents to an array using [$addtoSet][$addtoSet], and you could remove documents from an array using [$pull][$pull], but you couldn't do both in the same operation, you had to send two separate update commands if you needed to remove some and add some.

With 4.2, now you can, because you can format your update as a pipeline, with multiple $set and $unset stages, which makes those things possible. However, since this is so new I had a really hard time finding examples of many of the things I wanted to do, so I started to collect some here for my reference (and yours).


	import javax.crypto.*;
	import javax.crypto.spec.GCMParameterSpec;
	import javax.crypto.spec.PBEKeySpec;
	import javax.crypto.spec.SecretKeySpec;
	import java.nio.ByteBuffer;
	import java.nio.charset.StandardCharsets;
	import java.security.InvalidAlgorithmParameterException;
	import java.security.InvalidKeyException;
	import java.security.NoSuchAlgorithmException;

	const net = require('net');

	process.on('message', (message, serverHandle) => {
	if (message === 'server') {
	createServerAndListen(serverHandle);
	}
	});

	function createServerAndListen(serverHandle) {
	const server = net.createServer(handleConenction);

	const {
	fork
	} = require('child_process');
	const net = require('net');
	const os = require('os');
	const numCPUs = os.cpus().length;

	const workers = [];

	// Fork workers

	const net = require('net');

	const handleConenction = (socket) => {
	console.log("New connection");

	socket.on('close', () => {
	console.log('Client has disconnected');
	});

	// Handle 'data' event to process data from the client

	const { fork } = require('child_process');
	const net = require('net');
	const os = require('os');
	const numCPUs = os.cpus().length;
	const workers = [];
	let workerIndex = 0;

	// Fork workers
	for (let i = 1; i <=numCPUs; i++) {
	const worker = fork('worker-round-robin-policy.js'); // Fork the worker process

	postgres:
	image: postgres:9.4
	volumes:
	- ./init.sql:/docker-entrypoint-initdb.d/init.sql

	console.time('eventlooplag');
	//event-loop timer phase
	setTimeout(() =>console.timeEnd('eventlooplag'), 100);
	/*blocking code, stalling event loop, delaying the execution of the setTimeout ie lag in the event loop
	*/
	const min = 2;
	const max = 3e6;
	const primes = [];
	function generatePrimes(start, range) {
	let isPrime = true;

	let stop = false;

	//event-loop timer phase
	//set stop to true after 100 ms
	setTimeout(() => stop = true, 100);

	/*blocking code
	Event loop timer phase or any other phase could not be executed
	*/

	--log_gc (Log heap samples on garbage collection for the hp2ps tool.)
	type: bool default: false
	--expose_gc (expose gc extension)
	type: bool default: false
	--max_new_space_size (max size of the new generation (in kBytes))
	type: int default: 0
	--max_old_space_size (max size of the old generation (in Mbytes))
	type: int default: 0
	--max_executable_size (max size of executable memory (in Mbytes))
	type: int default: 0