How to search for a particular word in whole document in firestore?

Question

I am trying to make an android app for college. I have a collection named users. All the students who create accounts are stored in this collection within a document named same as their particular UID. I have a field inside every document named admission_id which contains a unique id. Whenever a student creates an account, he/she needs to enter a unique admission_id. I need to check whether the entered admission id is unique or not.

collectionReference = (CollectionReference) fStore.collection("Users");
Query query = collectionReference
        .whereEqualTo("Admission", "1234");
query.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
    @Override
    public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
        Toast.makeText(CreateStudent.this, "Admission ID already exists", Toast.LENGTH_SHORT).show();
    }
});

I tried the above code but it always returns true. I want to check 1234 in all the collections "Admission" field and display toast if it exist.

Answer 1

The onSuccess will always be called, even when there are no results.

To check whether there are any results for the query, check queryDocumentSnapshots.isEmpty() .

query.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
    @Override
    public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
        if (!queryDocumentSnapshots.isEmpty()) {
            Toast.makeText(CreateStudent.this, "Admission ID already exists", Toast.LENGTH_SHORT).show();
        }
    }
});