CODEWITHSUNDEEP
androidgoogle-cloud-firestore
DValdir Martins
DValdir Martins

Reputation: 181

How to query users collection using array of IDs from group collection

I have a collection where I store user groups. Each group has a group name, group limit and an array of users ID's.

I wonder how the best way to retrieve one group details and then users details, like name, photo, etc.

Right now, I am doing two queries to the database. First retrieving the group data(name, etc), second getting a list of users who has in the user details the information of the group ID:

"syncDesp = a4sQ27xb1wuD2rhONU2K"

I'm afraid of calling the database to many times.

// Get Group details
Preferencias prefs = new Preferencias(view.getContext());
listenGroups = pFirestore.collection("syncDesps").document(prefs.getSyncDesp()).addSnapshotListener((documentSnapshot, e) -> {
    if(e != null){
        Log.i("dados erro", Objects.requireNonNull(e).getMessage());
    }
    if(documentSnapshot != null){
        String nomeGrupo = Objects.requireNonNull(documentSnapshot.get("nomeGrupo")).toString();
        textNomeGrupo.setText(nomeGrupo);
        ArrayList membrosGrupo = (ArrayList) Objects.requireNonNull(documentSnapshot.get("syncDesp"));

    }
});

// Get User Details
FirebaseFirestore grupoFire = FirebaseFirestore.getInstance();
grupoFire.collection("usuarios")
        .whereEqualTo("syncDesp", prefs.getSyncDesp())
        .addSnapshotListener((queryDocumentSnapshots, e1) -> {
            listaUsuarios.clear();
            if(e != null){
                Log.i("dados erro", Objects.requireNonNull(e1).getMessage());
            }
            for(DocumentSnapshot usuarioSnapshot : Objects.requireNonNull(queryDocumentSnapshots).getDocuments()){
                String idU = (usuarioSnapshot.get("id") == null) ? "" : Objects.requireNonNull(usuarioSnapshot.get("id")).toString();
                String nomeUsuario = (usuarioSnapshot.get("nome") == null) ? "" : Objects.requireNonNull(usuarioSnapshot.get("nome")).toString();
                String fotoUsuario = (usuarioSnapshot.get("imgUsuario") == null) ? "" : Objects.requireNonNull(usuarioSnapshot.get("imgUsuario")).toString();

                UsuarioMeuGrupo usuarioMeuGrupo = new UsuarioMeuGrupo();//
                usuarioMeuGrupo.setIdUsuario(idU);
                usuarioMeuGrupo.setNome(nomeUsuario);
                usuarioMeuGrupo.setFoto(fotoUsuario);
                listaUsuarios.add(usuarioMeuGrupo);
            }

            adaptera.setOnItemClickRemoverListener(uMeuGrupo -> {
                Log.i("dados uMeuGrupo Clic", uMeuGrupo.getNome());
            });
            adaptera.notifyDataSetChanged();
        });

Group collection

I wonder if I should query the group collection separately from the users collection or if there is a way of making only one function to retrieve data from both collections.

Upvotes: 0

Views: 267

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317467

It's not possible to make a single query in Cloud Firestore span multiple collections. There is no join-like operation like you have in SQL. The only exception to this is collection group queries, which doesn't apply to your situation.

What you're doing right now is probably the best you can do with the database structure you have. If you want fewer queries, you'll have to do something to restructure your data to support that.

Upvotes: 1

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