Firecode

Firecode is a Node.js library that lets you efficiently traverse Firestore collections.

When you have millions of documents in a collection, you can't just get all of them at once as your machine's memory will explode. Firecode's configurable traverser objects let you do this in a simple, intuitive and memory-efficient way using batching.

Firecode is an extremely light, well-typed, zero-dependency library that is useful in a variety of scenarios. You can use it in database migration scripts (e.g. when you need to add a new field to all docs) or a scheduled Cloud Function that needs to check every doc in a collection periodically or a locally run script that retrieves some data from a collection.

Installation

Firecode is designed to work with the Firebase Admin SDK so if you haven't already installed it, run

npm install firebase-admin

Then run

npm install @firecode/admin

Quick Start

Suppose we want to send an email to all our users. We have a users collection that needs to be traversed. The following piece of code uses a Firecode traverser to do this simply and efficiently.

import { firestore } from 'firebase-admin';
import { createTraverser } from '@firecode/admin';

const usersCollection = firestore().collection('users');

const traverser = createTraverser(usersCollection, {
  // We want each batch to have 500 docs. Obviously, the size of the very last batch may be less than 500
  batchSize: 500,
  // We want to wait before moving to the next batch
  sleepBetweenBatches: true,
  // We'll wait 500ms before moving to the next batch
  sleepTimeBetweenBatches: 500,
});

const { batchCount, docCount } = await traverser.traverse(async (snapshots) => {
  const batchSize = snapshots.length;

  const sendEmailToEachUserInBatch = () =>
    Promise.all(
      snapshots.map(async (snapshot) => {
        const { email, firstName } = snapshot.data();
        await sendEmail({ to: email, content: `Hello ${firstName}!` });
      })
    );

  await sendEmailToEachUserInBatch();

  console.log(`Successfully emailed ${batchSize} users in this batch.`);
});

console.log(`Traversal done! We emailed ${docCount} users in ${batchCount} batches!`);

We are doing 3 things here:

Create a reference to the users collection
Pass that reference to the createTraverser() function and create the traverser with our desired configuration
Invoke .traverse() with an async callback that is called for each batch of document snapshots

This pretty much sums up the core functionality of this library! The .traverse() method returns a Promise that resolves when the entire traversal finishes, which can take a while if you have millions of docs. The Promise resolves with an object containing the traversal details e.g. the number of docs you touched.

More Examples

Add a new field

const projectsCollection = firestore().collection('projects');
const migrator = createBatchMigrator(projectsCollection, { batchSize: 250 });

const { migratedDocCount } = await migrator.update('isCompleted', false);
console.log(`Successfully updated ${migratedDocCount} projects!`);

Add a new field derived from the previous fields

type UserDoc = {
  firstName: string;
  lastName: string;
};

const usersCollection = firestore().collection('users') as firestore.CollectionReference<UserDoc>;
const migrator = createBatchMigrator(usersCollection, { batchSize: 250 });

const { migratedDocCount } = await migrator.update((snap) => {
  const { firstName, lastName } = snap.data();
  return {
    fullName: `${firstName} ${lastName}`,
  };
});
console.log(`Successfully updated ${migratedDocCount} users!`);

Rename an optional field

type UserPostDoc = {
  text: string;
  postedAt?: firestore.Timestamp;
};

const userPostsCollectionGroup = firestore().collectionGroup(
  'posts'
) as firestore.CollectionGroup<UserPostDoc>;
const migrator = createBatchMigrator(userPostsCollectionGroup, { batchSize: 250 });

const { migratedDocCount } = await migrator.update(
  (snap) => {
    const { postedAt } = snap.data();
    return {
      publishedAt: postedAt!, // Safe to assert
      postedAt: firestore.FieldValue.delete(),
    };
  },
  (snap) => snap.data().postedAt !== undefined // Ignore if it doesn't have a `postedAt` field
);
console.log(`Successfully updated ${migratedDocCount} users!`);

API

You can find the full API reference for @firecode/admin here.

License

This project is made available under the MIT License.

Evilweed/firecode