how to search in sub collection with firebase firestore

Question

I want to search in all sub-collections in firebase

  return database
    .collection("students")
    .doc(/* usually I pass the student id here but want to get exams for all students */)
    .collection("exams")
    .where("score", ">=", 4)
    .get()

is this possible to do? is too late to change my database and store exams in one collection and students in another one. unfortunately. thank you

Answer 1

To search across multiple collections in Firestore you can use a collection group query , which queries all collections with a specific name.

So if you want to search the exams subcollections of all students, that'd be:

database
    .collectionGroup("exams")
    .where("score", ">=", 4)
    .get()