Running a nested query in Cloud Firebase?-CodePudding

I'm messing around with Cloud Firestore. Trying to decide whether I should use it for my next project.

I would like to make a nested query, but all the tutorials and examples I found in the official documentation only query objects which are 2 levels deep and most of the time direct key/id calling.

I need something which is I believe called "nested query" I may be wrong on that one though, maybe it is not the correct phrase for such a thing in NoSQL which I just started to learn.

This is a skeleton/pilot app for a game where users can create characters. and I would like to query whether a character's name is already taken or not.

Here is my simple DB structure:

The main collection is named "users"

In "users" I have user documents.

In each user document, I have a collection named "characters"

In "characters" I have character documents.

In each character document there are two fields, name and level.

I tried it various ways with queries and the closest thing I could get was iterating through the whole thing which I believe is not the perfect solution.

Can somebody please help me to write an efficient nested query whether "Example Name" is already an existing character in the DB and tell me what is the correct way when you want to write like "infinitely deep" nested queries?

CodePudding user response：

If each user document contains a sub-collection that has the same ("characters") name, then I think you are looking for a collection group query. So a query should look like this:

val queryByName = db.collectionGroup("characters").whereEqualTo("name", "Adam");

Don't also forget to create an index.

Besides that, Firestore is as fast as it is at level 1 is also at level 100. So no worries.