Firebase - Structuring Data For Efficient Indexing - firebase

I've read almost everywhere about structuring one's Firebase Database for efficient querying, but I am still a little confused between two alternatives that I have.
For example, let's say I want to get all of a user's "maxBenchPressSessions" from the past 7 days or so.
I'm stuck between picking between these two structures:
In the first array, I use the user's id as an attribute to index on whether true or false. In the second, I use userId as the attribute NAME whose value would be the user's id.
Is one faster than the other, or would they be indexed a relatively same manner? I kind of new to database design, so I want to make sure that I'm following correct practices.
PROGRESS
I have come up with a solution that will both flatten my database AND allow me to add a ListenerForSingleValueEvent using orderBy ONLY once, but only when I want to check if a user has a session saved for a specific day.
I can have each maxBenchPressSession object have a key in the format of userId_dateString. However, if I want to get all the user's sessions from the last 7 days, I don't know how to do it in one query.
Any ideas?

I recommend to watch the video. It is told about the structuring of the data very well.
References to the playlist on the firebase 3
Firebase 3.0: Data Modelling
Firebase 3.0: Node Client

As I understand the principle firebase to use it effectively. Should be as small as possible to query the data and it does not matter how many requests.
But you will approach such a request. We'll have to add another field to the database "negativeDate".
This field allows you to get the last seven entries. Here's a video -
https://www.youtube.com/watch?v=nMR_JPfL4qg&feature=youtu.be&t=4m36s
.limitToLast(7) - 7 entries
.orderByChild('negativeDate') - sort by date
Example of a request:
const ref = firebase.database().ref('maxBenchPressSession');
ref.orderByChild('negativeDate').limitToLast(7).on('value', function(snap){ })

Then add the user, and it puts all of its sessions.
const ref = firebase.database().ref('maxBenchPressSession/' + userId);
ref.orderByChild('negativeDate').limitToLast(7).on('value', function(snap){ })

Related

How to get highest 10 scores with RestClient Unity from Firebase Realtime Database

I want to retrieve highest 10 scores from firebase . When i search stackoverflow i found some answers on here Firebase retrieve highest 100 score but i can not imagine how to implement them with REST API . My code is like this. I send request to end point and get response .
RestClient.Get<User>(databaseURL + getScoreText.text + ".json").Then(response =>
{
user = response;
UpdateScore();
});
Also for 2nd way, i can get all users' info by some json parser package and parse them and get the highest scores . But if my database gets bigger , i think i ll have problems . I need a way like "orderby". Do you know any way to implement "orderby" method to my restclient code ?
Reading the firebase docs:
Filtered data is returned unordered: When using the REST API, the filtered results are returned in an undefined order since JSON interpreters don't enforce any ordering. If the order of your data is important you should sort the results in your application after they are returned from Firebase.
It seems like scaling is a real limitation of the realtime database.
Firestore can do this pretty easily if you want to switch.
If you're sticking with realtime DB, I would save a separate database-reference that only ever contains the top 10 scores.
So when a player gets a new score, they would only upload it to this reference if it's higher than the 10th top score. This would mean you would only have a DB reference containing 10 or less top scores, and scaling wouldn't be a problem. I'm not very familiar with realtime DB, but I'm sure you could write a security to rule to enforce this in a secure, server authoritative manner, at the very least a cloud function.

Cloud Firestore and data modeling: From RDBMS to No-SQL

I am building an iOS app that is using Cloud Firestore (not Firebase realtime database) as a backend/database.
Google is trying to push new projects towards Cloud Firestore, and to be honest, developers with new projects should opt-in for Firestore (better querying, easier to scale, etc..).
My issue is the same that any relational database developer has when switching to a no-SQL database: data modeling
I have a very simple scenario, that I will first explain how I would configure it using MySQL:
I want to show a list of posts in a table view, and when the user clicks on one post to expand and show more details for that post (let say the user who wrote it). Sounds easy.
In a relational database world, I would create 2 tables: one named "posts" and one named "users". Inside the "posts" table I would have a foreign key indicating the user. Problem solved.
Poor Barry, never had the time to write a post :(
Using this approach, I can easily achieve what I described, and also, if a user updates his/her details, you will only have to change it in one place and you are done.
Lets now switch to Firestore. I like to think of RDBMS's table names as Firestore's collections and the content/structure of the table as the documents.
In my mind i have 2 possible solutions:
Solution 1:
Follow the same logic as the RDBMS: inside the posts collection, each document should have a key named "userId" and the value should be the documentId of that user. Then by fetching the posts you will know the user. Querying the database a second time will fetch all user related details.
Solution 2:
Data duplication: Each post should have a map (nested object) with a key named "user" and containing any user values you want. By doing this the user data will be attached to every post it writes.
Coming from the normalization realm of RDBMS this sounds scary, but a lot of no-SQL documents encourage duplication(?).
Is this a valid approach?
What happens when a user needs to update his/her email address? How easily you make sure that the email is updated in all places?
The only benefit I see in the second solution is that you can fetch both post and user data in one call.
Is there any other solution for this simple yet very common scenario?
ps: go easy on me, first time no-sql dev.
Thanks in advance.
Use solution 1. Guidance on nesting vs not nesting will depend on the N-to-M relationship of those entities (for example, is it 1 to many, many to many?).
If you believe you will never access an entity without accessing its 'parent', nesting may be appropriate. In firestore (or document-based noSQL databases), you should make the decision whether to nest that entity directly in the document vs in a subcollection based on the expect size of that nested entity. For example, messages in a chat should be a subcollection, as they may in total exceed the maximum document size.
Mongo, a leading noSQL db, provides some guides here
Firestore also provided docs
Hope this helps
#christostsang I would suggest a combination of option 1 and option 2. I like to duplicate data for the view layer and reference the user_id as you suggested.
For example, you will usually show a post and the created_by or author_name with the post. Rather than having to pay additional money and cycles for the user query, you could store both the user_id and the user_name in the document.
A model you could use would be an object/map in firestore here is an example model for you to consider
posts = {
id: xxx,
title: xxx,
body: xxx,
likes: 4,
user: {refId: xxx123, name: "John Doe"}
}
users = {
id: xxx,
name: xxx,
email: xxx,
}
Now when you retrieve the posts document(s) you also have the user/author name included. This would make it easy on a postList page where you might show posts from many different users/authors without needed to query each user to retrieve their name. Now when a user clicks on a post, and you want to show additional user/author information like their email you can perform the query for that one user on the postView page. FYI - you will need to consider changes that user(s) make to their name and if you will update all posts to reflect the name change.

Efficiently storing and retrieving likes

In my Firebase database I have posts and then authenticated users can "like" posts. How can I efficiently get the number of likes a post has received. I know using MongoDB I can add/remove the user's id to a list and then use a MongoDB function to get the length of it very quickly and set that equal to the likes amount, but I'm not suer how to do that using Firebase. I could also add/remove it to the list and increment a likeCount variable, but that seems like it would cause concurrency issues unless Firebase has a function for that. What functions can I call to best handle this and scale well? Thanks in advance!
You can do both things:
1) Create a votes node with the UID as key and a value to sum up all the votes.
post:{
//All the data
likes:{
$user_1:1,
$user_2:-1,
}
}
And then just get a SingleValue Event or a Value event(depending if you want to keep track of changes) and sum up all the children
2)You can use a transaction block and just save a value and increase or decrease it depending on the votes
(here is a link where you can find transactions for android,iOS or java)
https://firebase.google.com/docs/database/web/save-data#save_data_as_transactions
post:{
//All the data,
likes:2,
}
It really depends on how much information you want to store, and what the user can do once he/she already voted for some post,
I would recommend using both, to keep flexibility for the user to like (like in Facebook) so he can unlike something and use the transaction with number to keep it scalable.. so if a post gets 1,000,000 likes you don't have to count the 1,000,000 likes every time someone loads the post

Firebase query for bi-directional link

I'm designing a chat app much like Facebook Messenger. My two current root nodes are chats and users. A user has an associated list of chats users/user/chats, and the chats are added by autoID in the chats node chats/a151jl1j6. That node stores information such as a list of the messages, time of the last message, if someone is typing, etc.
What I'm struggling with is where to make the definition of which two users are in the chat. Originally, I put a reference to the other user as the value of the chatId key in the users/user/chats node, but I thought that was a bad idea incase I ever wanted group chats.
What seems more logical is to have a chats/chat/members node in which I define userId: true, user2id: true. My issue with this is how to efficiently query it. For example, if the user is going to create a new chat with a user, we want to check if a chat already exists between them. I'm not sure how to do the query of "Find chat where members contains currentUserId and friendUserId" or if this is an efficient denormalized way of doing things.
Any hints?
Although the idea of having ids in the format id1---||---id2 definitely gets the job done, it may not scale if you expect to have large groups and you have to account for id2---||---id1 comparisons which also gets more complicated when you have more people in a conversation. You should go with that if you don't need to worry about large groups.
I'd actually go with using the autoId chats/a151jl1j6 since you get it for free. The recommended way to structure the data is to make the autoId the key in the other nodes with related child objects. So chats/a151jl1j6 would contain the conversation metadata, members/a151jl1j6 would contain the members in that conversation, messages/a151jl1j6 would contain the messages and so on.
"chats":{
"a151jl1j6":{}}
"members":{
"a151jl1j6":{
"user1": true,
"user2": true
}
}
"messages":{
"a151jl1j6":{}}
The part where this gets is little "inefficient" is the querying for conversations that include both user1 and user2. The recommended way is to create an index of conversations for each user and then query the members data.
"user1":{
"chats":{
"a151jl1j6":true
}
}
This is a trade-off when it comes to querying relationships with a flattened data structure. The queries are fast since you are only dealing with a subset of the data, but you end up with a lot of duplicate data that need to be accounted for when you are modifying/deleting i.e. when the user leaves the chat conversation, you have to update multiple structures.
Reference: https://firebase.google.com/docs/database/ios/structure-data#flatten_data_structures
I remember I had similar issue some time ago. The way how I solved it:
user 1 has an unique ID id1
user 2 has an unique ID id2
Instead of adding a new chat by autoId chats/a151jl1j6 the ID of the chat was id1---||---id2 (superoriginal human-readable delimeter)
(which is exactly what you've originally suggested)
Originally, I put a reference to the other user as the value of the chatId key in the users/user/chats node, but I thought that was a bad idea in case I ever wanted group chats.
There is a saying: https://en.wikipedia.org/wiki/You_aren%27t_gonna_need_it
There might a limitation of how many userIDs can live in the path - you can always hash the value...

Sync related data using angularfire/collection

I want to use angularfirecollection to keep one-way sync with a list of data. The structure is a list of 'things' with various properties (e.g. 'Likes') and users who each hold a subset of 'things' keys (e.g. -jsdzsdrestofkey: true). U
sing angularfirecollection (or firebase native 'on'), I can sync up all things that a particular user has... I can also grab (using firebase native 'once') each 'thing''s properties to display.
In angular, however, I need to use $apply() to inject the property data into scope for each item in the user's 'thing' list. To keep things in sync, I suppose I can use firebase's on change event... But this all requires me to create new references for each thing in a user's list.
What is the best way to approach grabbing relational data in firebase, while keeping both the list and the relational data in sync?
Thanks!
Irfaan
If I understand correctly, it sounds like you should use FirebaseIndex and feed the index directly into an angularFireCollection. Then you wouldn't need to use $apply since the thing data will already be in the $scope, and everything will stay synced:
var index = new FirebaseIndex(fb.child('users/789/thing_list'), fb.child('things'));
$scope.things = angularFireCollection(index);
// $scope.things will contain the user's things with the associated thing data

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