how to access firestore from firebase functions

Question

I have started a Firebase project for a serverless web application. From the client-side I can access the Firestore database. From the serverless-side I have written a function to be called on http request. The function is trying to access the database by means of a Firestore object but it is failing because the Firestore object has no collection() function as I think it should have. In the output I show the content of the Firestore object.

const functions = require('firebase-functions');

exports.noteList = functions.https.onRequest((req, res) => {
  db = functions.firestore;
  console.dir(db);
  db.collection("notes").listDocuments().then(documentRefs => {
   return db.getAll(documentRefs);
  }).then(documentSnapshots => {
   res.json(documentSnapshots);
  });
});

output:

{ provider: 'google.firestore',
  service: 'firestore.googleapis.com',
  defaultDatabase: '(default)',
  document: [Function: document],
  namespace: [Function: namespace],
  database: [Function: database],
  _databaseWithOpts: [Function: _databaseWithOpts],
  _namespaceWithOpts: [Function: _namespaceWithOpts],
  _documentWithOpts: [Function: _documentWithOpts],
  DatabaseBuilder: [Function: DatabaseBuilder],
  NamespaceBuilder: [Function: NamespaceBuilder],
  snapshotConstructor: [Function: snapshotConstructor],
  beforeSnapshotConstructor: [Function: beforeSnapshotConstructor],
  DocumentBuilder: [Function: DocumentBuilder] }
Function crashed
TypeError: db.collection is not a function

For comparison this is how I access the database from the client-side, this is working:

function main() {
  var db = firebase.firestore();
  db.collection("global").doc("public").get().then(
    function(r) {
      var number_span = document.getElementById("number_span");
      data = r.data();
      number_span.textContent = "" + data.counter;
    });
}

Of course the firebase object is obtained in different ways. Maybe some configuration is missing?

Answer 1

You need to use a Firestore SDK (typically via the Firebase Admin SDK) to access Firestore. The Cloud Functions SDK (firebase-functions) does not do this for you. All it does is help you specify the functions you want to deploy. The body of the function should use the Firestore SDK.

// require and initialize the admin SDK
const admin = require('firebase-admin');
admin.initializeApp();

// now use the SDK in the body of the function
admin.firestore().collection(...).doc(...)

The Admin SDK just wraps the Cloud Firestore Node SDK, so use its reference to navigate the APIs.