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A 'days' node with more than 1 child isn't getting removed. How can I fix this issue?

I need to ensure that my promise bubbles up to the last then() on the top-level. So I need a return before collectionRef.once. But that return statement now prevents the collectionRef.once from happening. I'm stuck!

Here's my code

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
const defaultDatabase = admin.database();

exports.deleteOldItems = functions.database.ref('/path/to/items/{pushId}')
.onWrite(event => {
  var ref = event.data.ref.parent; // reference to the items
  var now = Date.now();
  var cutoff = now - 2 * 60 * 60 * 1000;
  var oldItemsQuery = ref.orderByChild('timestamp').endAt(cutoff);
  return oldItemsQuery.once('value', function(snapshot) {
    // create a map with all children that need to be removed
    var updates = {};
    snapshot.forEach(function(child) {
      updates[child.key] = null
    });
    // execute all updates in one go and return the result to end the function
    return ref.update(updates);
  }).then(function() {;

    const theRef = event.data.ref;
    const collectionRef = theRef.parent.child('days');
    return collectionRef; // ILEGAL RETURN STATEMENT
    collectionRef.once('value').then(messagesData => {
        if(messagesData.numChildren() > 1) {

  let updates = {};
updates['/days'] = null;
return defaultDatabase.ref().update(updates); // 'days' doesn't get removed even if it has more than 1 child (as in the image)!
        }
    })
});

});

Data structure: https://i.stack.imgur.com/gVn8S.jpg

  • Can you please stop duplicating questions, stick to one topic, no need to spam with same [question](https://stackoverflow.com/questions/44743530/node-with-more-than-1-child-is-not-getting-removed) – Mihai Iorga Jun 30 '17 at 07:20
  • @MihaiIorga Nobody's answering. I'll accept the correct answer. –  Jun 30 '17 at 07:31

1 Answers1

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exports.deleteOldItems = functions.database.ref('/path/to/items/{pushId}')
  .onWrite(event => {
    var ref = event.data.ref.parent // reference to the items
    var now = Date.now()
    var cutoff = now - 2 * 60 * 60 * 1000
    var oldItemsQuery = ref.orderByChild('timestamp').endAt(cutoff)
    return oldItemsQuery.once('value', function(snapshot) {
      // create a map with all children that need to be removed
      var updates = {}
      snapshot.forEach(function(child) {
        updates[child.key] = null
      })
      // execute all updates in one go and return the result to end the function
      return ref.update(updates)
    }).then(function() {
      // const theRef = event.data.ref
      const collectionRef = defaultDatabase.ref().child('/days')
      // return collectionRef // ILEGAL RETURN STATEMENT
      collectionRef.once('value').then(messagesData => {
                console.log(`Hello messageData : ${messagesData.numChildren()}`)
              if(messagesData.numChildren() > 1) {
                    const updates = {}
                    updates['/days'] = null
                    return defaultDatabase.ref().update(updates); // 'days' doesn't get removed even if it has more than 1 child (as in the image)!
                }
      })
  })

use defaultDatabase.ref().child('/days') instead of using event.data.ref.parent

also please go through the documentation and learn how promises works it will help you future. For now these changes will work.Tested at my end.

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What's the difference between event.data.ref and event.data.adminRef? - #AskFirebase Asynchronous Programming (I Promise!) with Cloud Functions for Firebase - Firecasts

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Ashutosh Barthwal
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  • Great answer. Accepted! But, but how do I check if `const collectionRef = defaultDatabase.ref().child('/days')` exists? –  Jun 30 '17 at 12:16
  • If it exists at the moment of `.onWrite`, I want to remove 'days'. If it doesn't at the moment of the `.onWrite`, I don't want 'days' to be removed. –  Jun 30 '17 at 12:19
  • i didn't get your question but i will try to answer it . you cannot remove something which doesn't exist so you dont have to worry about removing something that doesn't exist. – Ashutosh Barthwal Jul 01 '17 at 04:00