I'm totally new to Firebase, and I'm trying to get my head round the best db model design for 'relational' data, both 1-1 and 1-many.
We are using the Firestore db (not the realtime db).
Say we have Projects which can contain many Users, and a User can be in multiple Projects
The UI needs to show a list of Users in a Project which shows things like email, firstname, lastname and department.
What is the best way to store the relationship?
An array of User ids in the Project document?
A map of Ids in the Project document?
Ive read the above approaches were recommended, but was that for realtime database? Firestore supports Sub Collections, which sound more appropriate...
A sub collection of Users in the Project document?
A separate collection mapping Project id to User id?
A Reference data type? I've read here https://firebase.google.com/docs/firestore/manage-data/data-types about Reference data type, which sounds like what I want, but I cant find any more on it!
If its just a map or array of Ids, how would you then retrieve the remaining data about the user? Would this have to sit in the application UI?
If its a sub collection of Users documents, is there any way to maintain data integrity? If a user changed their name, would the UI / a cloudFunction then have to update every entry of that users name in the Sub collections?
any help / pointers appreciated...
The approach for modeling many-to-many relationships in Firestore is pretty much the same as it was in Firebase's Realtime Database, which I've answered here: Many to Many relationship in Firebase. The only difference is indeed that you can store the lookup list in a sub-collection of each project/user.
Looking up the linked item is also the same as before, it indeed requires loading them individually from the client. Such a client-side join is not nearly as slow as you may initially expect, so test it before assuming it can't possibly be fast enough.
Ensuring data integrity can be accomplished by performing batched writes or using transactions. These either completely succeed or completely fail.
Related
I have the following problem while trying to find the best data structure in firebase cloud firestore (NoSql) for a group travel app.
To put it as simple as I can... We have users. A user creates a new trip where he can include his friends. Those friends would also see the trip they where added to.
In a relational data base, we could represent this with 3 tables: Users - UsersTrips - Trips, where UsersTrips would have foreign key to UserId and TripId.
How can I map this problem to NoSql data base? In particulary, to firestore? I guess this is a many-to-many problem, because a trip could hold many users and a user can participate in many trips.
I had a wrong aproach of having a document "trips" that holds an array of the uids of users, but I find it a little bit strange.
I am building a firebase web application. Here is a simplified Firestore structure:
...
- ...
ITEMS
- item1
PHOTOS
- photo1
uid
VIDEOS
- item2
USERS
- uid1
displayName
...
- uid2
- ...
When someone accesses a photo or video I want to display the appropriate displayName and profilePhoto for that item.
I see two possible solutions:
Store only user UID in items. On every load, get user data from USERS collection or Then loop in user's UIDs and connect them with item UIDs. This would be done on every call. When users update displayName or profilePhoto, there wouldn't be any problem.
Store user UID, displayName, and profilePhoto path on the item. When users update data I would need to run a cloud function which would then update all items with new data.
How should I approach this and is there any other approach that I should consider? I lean towards the second solution.
What you have are the two most common approaches. The first is commonly referred to as performing a client-side join, while the second is duplicating/denormalizing the necessary data.
Neither is pertinently better than the other, but folks who are new to NoSQL databases are typically hesitant to duplicate data so tend to gravitate to performing client-side joins.
As you gain experience in NoSQL data models, you'll learn the right questions to ask yourself. For example: how often do a display name and profile photo change in my app? If that happens infrequently, duplicating those values in each item will make my reading code a lost simpler, faster, and more scalable.
For more good reading/watching on this:
How to write denormalized data in Firebase
NoSQL data modeling
Todd's excellent video series: Getting to know Cloud Firestore
is there any better way to get multiple specific data from collection in firestore?
Let's say have this collection:
--Feeds (collection)
--feedA (doc)
--comments (collection)
--commentA (doc)
users_in_conversation: [abcdefg, hijklmn, ...] //Field contains list of all user in conversation
Then, I'll need to retrieve the user data (name and avatar) from the Users collection, currently, I did 1 query per user, but it will be slow when there are many people in conversation.
What's the best way to retrieve specific users?
Thanks!
Retrieving the additional names is actually a lot faster than most developers expect, as the requests can often be pipelined over a single HTTP/2 connection. But if you're noticing performance problems, edit your question to show the code you use, the data you have, and the performance you're getting.
A common way to reduce the need to load additional documents is by duplicating data. For example, if you store the name and avatar of the user in each comment document, you won't need to look up the user profile every time you read a comment.
If you come from a background in relational databases, this sort of data duplication may be very unexpected. But it's actually quite common in NoSQL databases.
You will of course then have to consider how to deal with updates to the user profile, for which I recommend reading: How to write denormalized data in Firebase While this is for Firebase's other database, the same concepts apply to Firebase. I also in general recommend watching Getting to know Cloud Firestore.
I have tried some solution, but I think this solution is the best for the case:
When a user posts a comment, write a field of array named discussions in the user document containing the feed/post id.
When user load on a feed/post, get all user data which have its id in the user discussions (using array-contains)
it’s efficient and costs fewer transaction processes.
Like the title suggests, I have a use case where I will write data to both firestore and realtime database. I am using the realtime database for operations that require live feedback to users and firestore to store data that will not really change but can be queried for more complex operations later on.
Due to my need of both databases, I would like to use the same UID when creating data in both databases to make it easy to retrieve in the future. The issue I have is determining which generated ID will satisfy the other service.
My thought process is since Realtime Database push ID is based on timestamp, it could create hot partitions for Firestore so indexing performance as data grows could get hurt in the future if I used the same ID there. But if I use firestore's generated ID in the realtime database, I will not have the data in the sorted fashion that realtime database creates pushed data.
I was wondering what solutions people used to tackle this use case and what options are available to me. Thanks!
If you need to order data, then simply store timestamps as fields instead of depending on the time-based sort order of Realtime Database push IDs. You can do this easily in both databases. Firestore makes obsolete the idea that unique IDs have any meaning other than simply being unique.
If you make sure your unique ID's are truly random like Firestore's, then you won't have any problems with indexing or writing documents.
I have a collection, itemsCollection, which contains a very large amount of small itemDocs. Each itemDoc has a subcollection, statistics. Each itemDoc also has a field "owner" which indicates which user owns the itemDoc.
itemsCollection
itemDoc1
statistics
itemDoc2
statistics
itemDoc3
statistics
itemDoc4
statistics
...
I also have a collection, usersCollection, which contains basic user info.
usersCollection
user1
user2
user3
...
Since each itemDoc belongs to a specific user, it's necessary to display to each user which itemDocs they own. I have been using the query:
db.collection("itemsCollection").where("owner", "==", "user1")
I am wondering if this will scale effectively, i.e. whenever itemsCollection gets to be millions of records? If not, is the best solution to duplicate each itemDoc and its statistics subcollection as a subcollection in the user document, or should I be doing something else?
As Alex Dufter, the product manager from Firebase, explained in one of days at Firebase Dev Summit 2017 that Firestore was inspired in many ways by the feed-back that they had on the Firebase Realtime Database over the years. They faced two types of issues:
Data modelling and querying. Firebase Realtime Database cannot query over multiple properties because it ussaly involves duplication data or cliend-side filtering, which we all already know that is some kind of messy.
Realtime Database does not scale automatically.
With this new product, they say that you can now build an app and grow it to planetary scale without changing a single line of code. Cloud Firestore is also a NoSQL database that was build specifically for mobile and web app development. It's flexible to build all kinds of apps and scalable to grow to any size.
So because the new database was build knowing this iusses, duplication data is not nedeed anymore. So you will not have to worry about using that line of code, even if your data will grow to millions of records, it will scale automatically. But one thing you need to remember, if you will use multiple conditions, don't forget to use the indexes by simply adding them in the Firebase console. Here are two simple examples from the offical documentation:
citiesRef.whereEqualTo("state", "CO").whereEqualTo("name", "Denver");
citiesRef.whereEqualTo("state", "CA").whereLessThan("population", 1000000);