Firebase - Firestore Collection Utilities

firestoreUtils.js

/*
 * Utility functions for mass updates to Firebase's firestore collections
 * Methods: iterate, update, delete, copy
 */

/**
 * @callback IterateCollectionCb
 * @param {import('firebase-admin').firestore.DocumentSnapshot} doc
 * @param {import('firebase-admin').firestore.WriteBatch} [batch]
 */

/**
 * Iterate an entire collection
 * @param {import('firebase-admin').firestore.CollectionReference} collectionRef
 * @param {IterateCollectionCb} fn - Callback that takes arguments:
 * doc - a DocumentSnapshot instance; batch - a WriteBatch instance (only if
 * `writeBatch` parameter is `true`)
 */
exports.iterateCollection = async (
  collectionRef,
  fn,
  {
    noCursor = false,
    getData = false,
    writeBatch = false,
    batchSize = 300,
  } = {},
) => {
  let last;
  while (true) {
    let query = collectionRef.orderBy('__name__').limit(batchSize);

    if (!noCursor && last) query = query.startAfter(last);

    const snap = await (getData ? query : query.select()).get();

    if (snap.size === 0) break;

    last = snap.docs[snap.docs.length - 1];

    if (writeBatch) {
      // Max docs for batch write is 500
      const batch = collectionRef.firestore.batch();
      for (const doc of snap.docs) fn(doc, batch);
      await batch.commit();
    } else {
      for (const doc of snap.docs) fn(doc);
    }
  }
};

/**
 * Delete an entire collection
 * @param {import('firebase-admin').firestore.CollectionReference} collectionRef
 */
exports.deleteCollection = async (collectionRef) => {
  await exports.iterateCollection(
    collectionRef,
    (doc, batch) => {
      batch.delete(doc.ref);
    },
    {
      writeBatch: true,
      noCursor: true,
    },
  );
};

/**
 * Update all data in a collection
 * @param {import('firebase-admin').firestore.CollectionReference} collectionRef
 * @param {function|Object} updateData - Can be a plain data object, or a callback
 * function that takes DocumentReference and returns a plain data object
 */
exports.updateCollection = async (collectionRef, updateData) => {
  const isFunc = typeof updateData === 'function';

  await exports.iterateCollection(
    collectionRef,
    (doc, batch) => {
      const updated = isFunc ? updateData(doc) : updateData;
      if (updated) batch.update(doc.ref, updated);
    },
    {
      writeBatch: true,
      getData: isFunc,
    },
  );
};

/**
 * Copies an entire collection to a new collection with name <newName>
 * @param {import('firebase-admin').firestore.CollectionReference} collectionRef
 * @param {String} newName
 * @param {Boolean} [deleteSourceCollection=false]
 */
exports.copyCollection = async (
  collectionRef,
  newName,
  deleteSourceCollection = false,
) => {
  const newCollec = collectionRef.firestore.collection(newName);

  await exports.iterateCollection(
    collectionRef,
    (doc, batch) => {
      batch.set(newCollec.doc(doc.id), doc.data());
    },
    {
      writeBatch: true,
    },
  );

  if (deleteSourceCollection) await exports.deleteCollection(collectionRef);
};