MatViewExperiment.js

function generateRandomString(length) {
  var randomString = ''
  while (randomString.length < length) {
    randomString += Math.random().toString(20).slice(2, length);
    if (randomString.length > length) return randomString.slice(0, length);
  }
  return randomString;
};

function generateRandomInt(min, max) {  // min and max included
  return Math.floor(Math.random() * (max - min + 1) + min)
}

const {MongoClient} = require('mongodb');
const Db = require('mongodb/lib/db');

const isDebugMode = false;
const numExperiments = 10000;
const connectionUrl = 'mongodb://localhost:27017'
const dbName = 'myTestDB'
const srcCollName = "srcColl";
const matViewCollName = "matViewColl";
const numDocs = 100000;

let client
let db
let adminDb

const init = () => MongoClient.connect(connectionUrl, {useNewUrlParser: true})
                       .then((theClient) => {
                         client = theClient;
                         adminDb = client.db('admin')
                         db = client.db(dbName);
                       })

async function runTest() {
  let coll = db.collection(srcCollName);
  console.log('Started preparation.');
  // Remove previous data.
  await db.collection(srcCollName).drop();
  await db.collection(matViewCollName).drop();

  // Insert some control documents.
  let data = []
  for (var i = 0; i < numDocs; ++i) {
    data.push({
      '_id': i+100,
      't': generateRandomInt(0, 10),
      'y': generateRandomInt(0, 1000),
      'w': generateRandomInt(0, 100),
      'a': generateRandomString(16)
    });
  }

  console.log('Created data.');

  await coll.insertMany(data);

  console.log('Inserted data.');


  try {
    console.log('Started running tests.');

    let startTime = new Date();

    for (var i = 0; i < numExperiments; ++i) {
      if(isDebugMode) console.log('Running test ' + (i+1) + '...');
      await runTestIteration(db, {debug: isDebugMode, sharded: false, transactional: false, updateView: true});
      if(isDebugMode) console.log('---------------------------------------------');
    }

    let endTime = new Date();
    let duration = endTime.getTime() - startTime.getTime();
    console.log('Ran experiment in ' + duration + ' ms.');
    console.log('Finished running tests.');
  } catch (e) {
    console.log('Errored while running tests.');
    throw e;
  }
}

async function printCollection(db, collName) {
  let coll = db.collection(collName);
  let arr = await coll.find().toArray()
  console.log(collName + ' = ' + JSON.stringify(arr));
}

async function runTestIteration(db, options) {
  let debug = options.debug;
  let sharded = options.sharded;
  let transactional = options.transactional;
  let updateView = options.updateView;
  let session = transactional ? client.startSession() : null;
  function addSession(opts) {
    if(transactional) {
      opts.session = session;
    }
    return opts;
  }
  let matViewUpdateFn = async () => {
    let coll = await db.collection(srcCollName);
    if(debug) await printCollection(db, srcCollName);
    await coll.updateOne({_id: 100 + generateRandomInt(0, numDocs-1)}, {$inc: { t: 2 }}, addSession({upsert: false, writeConcern: "majority"}));
    if(debug) await printCollection(db, srcCollName);

    if(updateView) {
      const matViewTempCollName = "matViewTempColl"+generateRandomString(10);
      await db.createCollection(matViewTempCollName, addSession({ writeConcern: "majority" }));
      if(sharded) {
        await adminDb.command({shardCollection: dbName+'.'+matViewTempCollName, key: {_id: 1}});
      }
      let matViewTempColl = await db.collection(matViewTempCollName);

      if(debug) console.log('created collection ' + matViewTempCollName);
      if(debug) await printCollection(db, matViewTempCollName);

      let aggOutRes
      if(!transactional) {
        aggOutRes = await coll.aggregate([{$group: {_id: "$y", t_avg: { $avg : "$t" }, w_avg: { $avg : "$w" }}}, {$merge: {into: matViewTempCollName, on: '_id'}}], addSession({'allowDiskUse': true})).toArray();
      } else {
        aggOutRes = await coll.aggregate([{$group: {_id: "$y", t_avg: { $avg : "$t" }, w_avg: { $avg : "$w" }}}], addSession({'allowDiskUse': true})).toArray();
        await matViewTempColl.insertMany(aggOutRes, addSession({ordered: false, writeConcern: "majority"}));
      }

      if(debug) console.log('The output keys for creating ' + matViewTempCollName + ' (using ' + srcCollName + ') = ' + JSON.stringify(aggOutRes));
      if(debug) await printCollection(db, matViewTempCollName);

      if(!transactional) {
        await matViewTempColl.rename(matViewCollName, addSession({dropTarget: true}));
        if(debug) await printCollection(db, matViewCollName);
        if(debug) console.log("Done with transaction.")
      }
    }
  }
  if(transactional) {
    await session.startTransaction();
      try{
        await matViewUpdateFn();
      } catch(err) {
        console.log(err);
      } finally {
        await session.commitTransaction();
        await session.endSession();
      }
  } else {
    await matViewUpdateFn();
  }
}