We have unstructured data and each document can have different subcollections.
We want to know get the names of all the subcollections present in a collection.

Currently we have to iterate over all the documents present in a collection and for each document we are pulling the list of subcollections present in it.
This process is very resource consuming and slow. We have to fire a query for each document present in the collection.

Please provide an api something like db.collection("collectioName").listSubCollectionNames();