Faster Firestore via Data Aggregation 

This should be top comment. Absolutely not production ready app. This is not cost effective to query all comments each time.

I suggest putting a "limit 100" on your query. that way it's production ready. Then in the user interface, if you get back 100, just show "100+". If you're getting more than 100 comments, you have other issues such as spam detection you need to take care of.

I may be mistaken for I haven't gone in depth in the docs but, is the "querySnapshot" not a reference to the documents that match the query from the indexes? Meaning the query isn't actually incurring a charge for reading the documents until forEach is executed?

BAM5 size contains the number of documents returned firebase.google.com/docs/reference/android/com/google/firebase/firestore/QuerySnapshot.html#size() But it contains all the documents even before the foreach :( Have to limit the number of documents expected directly in the query request ;)

You can have the trick in the firebase channel. I forgot which videos, but I think it is one of the newest video about pricing. Basically you can just use math, save savedCommentsCount + 1 or something like that, u don't have to re-read all the doc in the collection

Thank you!

Hey Diago, Good approach, but correct me if i am wrong. Till this point that "we need to isolate reviews/comments in to a separate model" we are on the same channel, right? If we query by limit on othher document then n of population queries will be made to reviews/comments collection (here n is number of posts) and reffing in mongodb is not thhat performant as Joins in SQL. Is that still a good approach, if you could share your thoughts

Thank you! Bunch of great content right now, hard to keep up.

There is a danger of a race condition. If you have a user add and then a user delete smultaneously you could have a condition where they both start from the same document count and attempt to modify at once. Say we start at 100 posts -1 Delete. 99 posts. Now the Add function is also running in the background and it read the 100 posts before updating and your post count is now "101" instead of 100. It's still possible for the number to be off with parallel operators but it'll never be more off than the current number of active functions. If you have 9 people all try to delete simultaneously you might go from 100 -1 (9x times) and end up at 99 instead of 91 comments. Now when someone adds a document even if it was 99, it'll still recount and end back up at 92.

@@im.thatoneguy hi Gavin, what if you did it with a transaction ?

@@basdfgwe This is a bit late, however, this wouldn't work. Transactions are not cross-user. You'd be best using a queue for the actions (increment, decrement) which invokes a cloud function and performs that action on that document. That way you'd only be writing to that content one at a time.

For anyone looking for answer to this, maybe you can just increment/decrement the counter based on the action without even reading all the comments doc. But for certain interval, update the counter to match the size of comments in the firestore. This way is more "cheap" but requires you to set up another service for scheduling the counter "cache" refresh job. Edit: race condition on post-comment case is totally fine. But if you need something more reliable, for ticket reservation for example, probably use SQL instead of NoSQL db.

@@dionricky hi Don, I didn't think there was a way of getting a count like what we have in SQL.

Thank you! Follow the link in the description to get the full code on github.

I'm not 100% sure how he's doing it, maybe editing, but I also vaguely recall there being an extension that does something similar to this for demonstrative purposes. I remember a coworker saying it'd be funny to troll someone by pretending to be doing something super complex super fast with it

Given the mouse movements I'm more inclined to think it is actually an extension

Thank you! The one-time membership is not currently discounted, but the monthly/quarterly is. You can cancel anytime. But with the lifetime you also get a free t-shirt :)

Angular Firebase Ah the t-shirt. See I need the lifetime plan ^^ The discount was only during Google I/O ?

Yes, but I will likely discount it again in the future. Not definite timeline tho.

Angular Firebase Ok. I'll wait for it then. Great job on the videos. You're helping a LOT

For the most part yes, but there were some changes in v1.0 that is causing your error firebase.google.com/docs/functions/beta-v1-diff

@@Fireship Thanks mate, got it sorted.

You are using a newer version of Firebase SDK for Cloud Functions than he is in this video. Check out the changes needed: firebase.google.com/docs/functions/beta-v1-diff. Here is how I changed the code he provided to get this working: const functions = require('firebase-functions'); const admin = require('firebase-admin'); admin.initializeApp(); exports.aggregateComments = functions.firestore .document('posts/{postId}/comments/{commentId}') .onWrite((change, context) => { const commentId = context.params.commentId; const postId = context.params.postId; Pretty much the same from there on out.

he thinks he is teaching to experts

Most of these videos are directed towards those who are "experts." If you want to learn angular, he has a beginners tutorial series.

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-jm66TSlVtcc.html :)