Firestore cloud function to recursively update subcollection/collectionGroup

问题

I have this cloud function:

import pLimit from "p-limit";


const syncNotificationsAvatar = async (
  userId: string,
  change: Change<DocumentSnapshot>
) => {
  if (!change.before.get("published") || !change.after.exists) {
    return;
  }

  const before: Profile = change.before.data() as any;
  const after: Profile = change.after.data() as any;
  const keysToCompare: (keyof Profile)[] = ["avatar"];
  if (
    arraysEqual(
      keysToCompare.map((k) => before[k]),
      keysToCompare.map((k) => after[k])
    )
  ) {
    return;
  }

  const limit = pLimit(1000);

  const input = [
    limit(async () => {
      const notifications = await admin
        .firestore()
        .collectionGroup("notifications")
        .where("userId", "==", userId)
        .limit(1000)
        .get()

      await Promise.all(
        chunk(notifications.docs, 500).map(
          async (docs: admin.firestore.QueryDocumentSnapshot[]) => {
            const batch = admin.firestore().batch();
            for (const doc of docs) {
              batch.update(doc.ref, {
                avatar: after.avatar
              });
            }
            await batch.commit();
          }
        )
      );
    })
  ];

  return await Promise.all(input);
};

How can I recursively update the notifications collection but first limit the query to 1.000 documents (until there are not more documents) and then batch.update them? I'm afraid this query will timeout since collection could grow big over time.

回答1:

Posting a solution I worked out, not following the context of the question though but it can easily be combined. Hope it helps someone else.

import * as admin from "firebase-admin";

const onResults = async (
  query: admin.firestore.Query,
  action: (batch: number, docs: admin.firestore.QueryDocumentSnapshot[]) => Promise<void>
) => {
  let batch = 0;
  const recursion = async (start?: admin.firestore.DocumentSnapshot) => {
    const { docs, empty } = await (start == null
      ? query.get()
      : query.startAfter(start).get());
    if (empty) {
      return;
    }
    batch++;
    await action(
      batch,
      docs.filter((d) => d.exists)
    ).catch((e) => console.error(e));
    await recursion(docs[docs.length - 1]);
  };
  await recursion();
};

const getMessages = async () => {
  const query = admin
    .firestore()
    .collection("messages")
    .where("createdAt", ">", new Date("2020-05-04T00:00:00Z"))
    .limit(200);

  const messages: FirebaseFirestore.DocumentData[] = [];

  await onResults(query, async (batch, docs) => {
    console.log(`Getting Message: ${batch * 200}`);
    docs.forEach((doc) => {
       messages.push(doc.data());
    });
  });
  return messages;
};

来源：https://stackoverflow.com/questions/61454219/firestore-cloud-function-to-recursively-update-subcollection-collectiongroup