CODEWITHSUNDEEP
google-cloud-firestore
Dusan Dimitrijevic
Dusan Dimitrijevic

Reputation: 3219

Firestore: Order by sub-collection field

First of all, this is not a regular question. It's little complicated.

App summary

Recipes app where users can search recipes by selected ingredients (collection ingredients exists in firestore db). I want to store for every ingredient statistics how much did users search with that selected ingredient, so I can show them later at the top ingredients which they used mostly for searching recipes.

This is how my collection looks like:

http://prntscr.com/nlz062

And now I would like to order recipes by statistics that created logged in user.

first = firebaseHelper
                    .getDb()
                    .collection(Constants.INGREDIENTS_COLLECTION)
                    .orderBy("statistics." + firebaseHelper.getCurrentUser().getUid() + ".count")
                    .limit(25);

If logged in user hasn't yet searched recipes with ingredients, then it should order normally. Anyway the query above is not working. Is it possible this use case to be done with Firestore.

Note: Statistics may exists or may not for logged in user, it all depends on his search.

Upvotes: 0

Views: 690

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317968

You can't query and documents by fields that don't immediately exist within the document. Or, in other words, you can't use fields documents within subcollections that are not in the named collection being queried.

As of today (using the latest Firestore client libraries), you could instead perform a collection group query to query all of the subcollections called "statistics" for their count field. However, that will still only get you the statictics documents. You would have to iterate those documents, parse the ingredient document ID out of its reference, and individually get() each one of those documents in order to display a UI.

The collection group query would look something like this in JavaScript:

firestore
    .collectionGroup("statistics")
    .where(FieldPath.documentId())
    .orderBy("count")
    .limit(25)

You should be able to iterate those results and get the related documents with no problem.

Upvotes: 1

Related Questions