Firebase Cloud function update all entries in database

Question

i have bunch of comments in Firebase database and i want to do some updates to the comments via Cloud Function ( this is simplified example, i will be doing some logic which doe

Answer 1

If you want to update all child nodes, you can do something like this:

var ref = firebase.database().ref("comments"); // or admin.database().ref("comments")
ref.once("value").then((snapshot) => {
  var updates = {};
  snapshot.forEach((commentSnapshot => {
    var comment = commentSnapshot.val();
    var newRating = comment.rating + 1000;
    updates[commentSnapshot.key+"/rating"] = newRating;
  });
  ref.update(updates);
})

This performs a single multi-location update for all comments. Note that the performance benefit over performing separate updates is quite small, since Firebase pipelines the multiple requests over a single connection.

Also note that you should not put this in a Cloud Functions trigger on /comments, since that will lead to an endless loop: every time the comments get written, your function triggers, which updates the comments, which triggers the function again.

If you need this in Cloud Functions, you'll want to use a HTTP-triggered function, which is triggered by HTTP calls instead of database writes.

exports.updateCommentRatings = functions.https.onRequest((req, res) => {
  var ref = admin.database().ref("comments")
  ref.once("value").then((snapshot) => {
    var updates = {};
    snapshot.forEach((commentSnapshot => {
      var comment = commentSnapshot.val();
      var newRating = comment.rating + 1000;
      updates[commentSnapshot.key+"/rating"] = newRating;
    });
    ref.update(updates).then(() => {
      res.status(200).send("Comment ratings updated");
    });
  })
})

You can then periodically call this URL/function with a service like cron-job.org. For more on this see Cloud Functions for Firebase trigger on time?.