How do we set a different database / namespace in Firestore? This would be helpful in building multi-tenancy SaaS products.
Based on the recent announcements by google, it looks this will become a thing:
Cloud Firestore, currently available in beta, is the next generation of Cloud Datastore, and offers compatibility with the Datastore API and existing client libraries. With the newly introduced Datastore mode on Cloud Firestore, you don’t need to make any changes to your existing Datastore apps to take advantage of the added benefits of Cloud Firestore. After general availability of Cloud Firestore, we will transparently live-migrate your apps to the Cloud Firestore backend, and you’ll see better performance right away, for the same pricing you have now, with the added benefit of always being strongly consistent. It’ll be a simple, no-downtime upgrade. Read more here about Cloud Firestore.
It's something being considered, but no firm plans yet.
The current method would require you to create separate projects. A collection name scheme might be possible, but you'll run into composite index limits for the project.
来源：https://stackoverflow.com/questions/46701324/namespaces-for-multi-tenancy-in-cloud-firestore