firestoreWritePerformance.js

//
// This script compares the performance of three common ways to perform
// bulk write operations on Firestore.
// 
// In test run of this script, it took:
// 
// 1. `~105.4s` when using sequential individual write operations
// 2. `~  2.8s` when using sequential batched write operations
// 3. `~  1.5s` when using parallel individual write operations
// 4. `~  1.5s` when using parallel batched write operations
// 
// For a full comparison, see 
// [What is the fastest way to write a lot of documents to Firestore?](https://stackoverflow.com/q/58897274).
//
// To use this script you will need to set the `GOOGLE_APPLITION_CREDENTIALS
// as described in the Firebase documentation on 
// [initializing the SDK](https://firebase.google.com/docs/admin/setup#initialize_the_sdk)
//

(async function() {

  var admin = require('firebase-admin');

admin.initializeApp({
  credential: admin.credential.applicationDefault()
});

let datas = [];
for (let i=0; i < 1000; i++) {
  let data = {};
  for (let j=0; j < 10; j++) {
    const random = Math.random();
    if (random < 0.2) {
      data["field"+j] = "";
      for (let k=0; k < Math.random()*10; k++) {
        data["field"+j] += Math.random().toString(36).substring(2, 15)
        if (Math.random() < 0.5) data["field"+j] += " ";
      }
    }
    else if (random < 0.4) {
      data["field"+j] = Math.random()
    }
    else if (random < 0.6) {
      data["field"+j] = Math.round(Math.random() * 100000);
    }
    else if (random < 0.8) {
      data["field"+j] = Math.random() < 0.5;
    }
    else if (random < 0.9) {
      data["field"+j] = new Date(Math.random() * Date.now());
    }
    else {
      data["field"+j] = admin.firestore.FieldValue.serverTimestamp()
    }
  }
  datas.push(data);
}

//console.log(datas);
let collection = admin.firestore().collection("58891568");

console.log(`Testing performance of writing ${datas.length} documents...`)
console.log(`There are now ${await getDocumentCount()} documents...\n`)

let timstamp;


timestamp = Date.now();
await testSequentialIndividualWrites(JSON.parse(JSON.stringify(datas)));
console.log(`sequential writes took ${Date.now() - timestamp} ms`);
console.log(`There are now ${await getDocumentCount()} documents...\n`)
  
timestamp = Date.now();
await testBatchedWrites(JSON.parse(JSON.stringify(datas)));
console.log(`Batched writes took ${Date.now() - timestamp} ms`);
console.log(`There are now ${await getDocumentCount()} documents...\n`)

timestamp = Date.now();
await testParallelBatchedWrites(JSON.parse(JSON.stringify(datas)));
console.log(`Parallel batched writes took ${Date.now() - timestamp} ms`);
console.log(`There are now ${await getDocumentCount()} documents...\n`)

timestamp = Date.now();
await testParallelIndividualWrites(JSON.parse(JSON.stringify(datas)));
console.log(`Parallel writes took ${Date.now() - timestamp} ms`);
console.log(`There are now ${await getDocumentCount()} documents...\n`)



async function testSequentialIndividualWrites(datas) {
  while (datas.length) {
    await collection.add(datas.shift());
  }
}

async function testBatchedWrites(datas) {
  let batch = admin.firestore().batch();
  let count = 0;
  while (datas.length) {
    batch.set(collection.doc(Math.random().toString(36).substring(2, 15)), datas.shift());
    if (++count >= 500 || !datas.length) {
      await batch.commit();
      batch = admin.firestore().batch();
      count = 0;
    }
  }
}

async function testParallelIndividualWrites(datas) {
  await Promise.all(datas.map((data) => collection.add(data)));
}

async function testParallelBatchedWrites(datas) {
  let batches = [];
  let batch = admin.firestore().batch();
  let count = 0;
  while (datas.length) {
    batch.set(collection.doc(Math.random().toString(36).substring(2, 15)), datas.shift());
    if (++count >= 500 || !datas.length) {
      batches.push(batch.commit());
      batch = admin.firestore().batch();
      count = 0;
    }
  }
  await Promise.all(batches);
}


async function getDocumentCount() {
  return (await collection.get()).size;
}


})();