Support backfill documents in subcollections

[eysenshi]

Description

This is a request to support backfill all subcollections return from a collection group query. This could be helpful in use case like, backfill landmarks data from all cities under path: cities/{cityId}/landmarks.

[jasonbosco]

Note to myself: docs for listening on dynamic paths: https://firebase.google.com/docs/functions/firestore-events#wildcards-parameters

[elhe26]

@jasonbosco, this extension supports subcollection paths? (ie. cities/{cityId}/landmarks)

[ChauCM]

Subcollection like "cities/{cityId}/landmarks" worked for me on indexToTypesenseOnFirestoreWrite but not on backfill: backfillToTypesenseFromFirestore. Basically the backfill function runs without error but no record is imported.

[guenth39]

@jasonbosco Any plans to implement this? I would really need this feature!

[guenth39]

The issue should be fixed by changing this line in the backfill cloud function

firestore-typesense-search/functions/src/backfillToTypesenseFromFirestore.js

Lines 43 to 44 in 44e01a7

	const querySnapshot =
	await admin.firestore().collection(config.firestoreCollectionPath).get();

In the case of a subcollection, we have to use collectionGroup instead of collection.

[jsasitorn]

Added a PR that adds support for this in #99 with additional checks on the collection path. Concern with a quick .collectionGroup("landmarks") approach in backfill is that it may accidentally capture unrelated entities. So you not only get "cities/{cityId}/landmarks" but also "towns/{townId}/landmarks"