问题
I understand that empty documents within collections are removed automatically by the system in Firestore. However, I have a situation now where the name of the document serves a purpose. I have a collection named usernames, and within this, many documents with the ID being the username. For instance, usernames/bob_marley is what I might see in the database. The problem here is that, since the documents do not have any fields in them, they get removed automatically thereby defeating the purpose of the set-up. How should I be structuring my database in these cases?
Thank you
回答1:
The easiest thing to do is simply not allow the document to ever become empty. Keep one property in it with (for example) "exists = true" and make sure it never gets removed. Use a security rule to prevent this, if you're concerned about users accidentally doing this to themselves.
Another thing to do is re-evaluate what exactly you're trying to do with an empty document in the system, and if it's worthwhile to think about how to structure your data in a way that best meets the queries you want to perform.
来源：https://stackoverflow.com/questions/48758395/creating-empty-documents-in-firestore