In my firebase db I have 3 collections:
Users
{user_id}: {name: "John Smith"}
Items
{item_id}: {value: 12345}
Actions
{action_id}: {action: "example", user: {user_id}, items:{item_id}}
Basically, instead of storing the Users and Items under the Actions Collection, I just keep an ID. But now I need a list of all actions and this also needs info from the Users and Items Collection. How can I efficiently query firebase so I can get a result that looks like this:
{
action: "example",
user: {
name: "John Smith"
},
item: {
value: 1234
}
}
Unfortunately, there is no such thing in firebase or a similar database, basically, you are looking for a traditional join, which is no recommended thing to do in a NoSQL database.
If you want to do it in firebase, you will need:
Get the element you are looking for from your main collection Actions in this case.
Then you need to do another call to the Items collections where item_id == action.item_id.
Then assign in the actions["Item"] = item_gotten.
This is not a recommended use as I said, usually, when you are using a NoSQL Database you are expecting a denormalize structure, from your application you need to save the whole Item, in the Action JSON, and also in the Item. Yes, you will have duplicate data but this is fine for this kind of model. also you shouldn't expect too many changes in one specific object within your whole object key If you are managing a big set of changes you could be using the incorrect kind of DB.
For aggregation queries reference, you might check: https://firebase.google.com/docs/firestore/solutions/aggregation
Related
I can't manage to determine what is the better way of organizing my database for my app :
My users can create items identified by a unique ID.
The queries I need :
- Query 1: Get all the items created by a user
- Query 2 : From the UID of an item, get its creator
My database is organized as following :
Users database
user1 : {
item1_uid,
item2_uid
},
user2 : {
item3_uid
}
Items database
item1_uid : {
title,
description
},
item2_uid : {
title,
description
},
item3_uid : {
title,
description
}
For the query 2, its quite simple but for the query 2, I need to parse all the users database and list all the items Id to see if there is the one I am looking for. It works right now but I'm afraid that it will slow the request time as the database grows.
Should I add in the items data a row with the user id ? If yes the query will be simpler but I heard that I am not supposed to have twice the same data in the database because it can lead to conflicts when adding or removing items.
Should I add in the items data a row with the user id ?
Yes, this is a very common approach in the NoSQL world and is called denormalization. Denormalization is described, in this "famous" post about NoSQL data modeling, as "copying of the same data into multiple documents in order to simplify/optimize query processing or to fit the user’s data into a particular data model". In other words, the main driver of your data model design is the queries you plan to execute.
More concretely you could have an extra field in your item documents, which contain the ID of the creator. You could even have another one with, e.g., the name of the creator: This way, in one query, you can display the items and their creators.
Now, for maintaining these different documents in sync (for example, if you change the name of one user, you want it to be updated in the corresponding items), you can either use a Batched Write to modify several documents in one atomic operation, or rely on one or more Cloud Functions that would detect the changes of the user documents and reflect them in the item documents.
In a Firestore security rule, I'm trying to check if the user attempting to create/delete a document in one collection is also the owner of that object, as marked in another collection. Basically, my data looks something like this:
In the users collection, each user has a document like this:
{
name: 'john',
userItems: [
{
id: 'random-id',
...
},
...
],
...
}
In the items collection (which I am writing the rule for), all of the items from all of the users of the platform are there, and have Firestore IDs which correspond to the id keys in the elements of the items list of their owners. So if john created an item with the id random-id, his user document would look like the above, and there would be a new document in the items collection with the Firestore ID of random-id.
What I am trying to achieve is to create a security rule wherein a document in the items collection can only be updated if the user document of the currently authed user, which I can access with get(/databases/$(database)/documents/users/$(request.auth.uid)), has an element in their userItems list which has the id key equal to request.resource.id. If this were normal JS, I'd probably do something like:
match /items/{item} {
allow write: if get(/databases/$(database)/documents/users/$(request.auth.uid))
.data
.userItems
.some(userItem =>
userItem.id === request.resource.id
)
}
However, the Firestore List interface is very lacklustre, and doesn't support fancy operations like .some, or even basic/manual looping (as far as I'm aware). I've been trying to come up with some clever way around this, but even .joining the list and .matching the resulting string with some fancy RegExp wouldn't work, since I'm pretty sure that maps would parse as '[object Object]' instead of stringifying properly.
Is there any way to do this using standard Firestore rules, without reconfiguring my DB structure?
What you're trying to do isn't possible with security rules. You will need to either change that way you represent your data (which I recommend, as a list is probably not the best representation), or add more data to satisfy your requirements.
If the the random-id is unique in the list, you should consider using a map instead of a list to represent it, so that you can do simple lookups on the Map that becomes available in rules. If your userItems field was a map indexed by that ID, you could instead say:
allow write: if get(...).data.userItems.keys().hasAny([request.resource.id]);
If for some reason you can't change the field, you will need to duplicate the IDs into a new list field and check it like this:
allow write: if get(...).data.userItemIds.hasAny([request.resource.id]);
I have a real-time database on firebase which consists of ListFields. Among these fields, one field, participants is a list of strings and two usernames. I want to make a query to firebase database such that it will return the documents in which a particular username is present in the participants list.
The structure of my document is as follows :
I want to make a query such that Firebase returns all the documents in which the participants list consists aniruddh. I am using Flutter with the flutterfire plugins.
Your current data structure makes it easy to find the participants for a conversation. It does however not make it easy to find the conversations for a user.
One alternative data structure that makes this easier is to store the participants in this format:
imgUrls: {},
participants: {
"aniruddh": true,
"trubluvin": true
}
Now you can technically query for the the conversations of a user with something like:
db.child("conversations").orderByChild("participants/aniruddh").equalTo(true)
But this won't scale very well, as you'll need to define an index for each user.
The proper solution is to add a second data structure, known as an inverted index, that allows the look up of conversations for a user. In your case that could look like this:
userConversations: {
"aniruddh": {
"-LxzV5LzP9TH7L6BvV7": true
},
"trubluvin": {
"-LxzV5LzP9TH7L6BvV7": true
}
}
Now you can look up the conversations that a user is part of with a simple read operation. You could expand this data structure to contain more information on each conversation, such as the information you want to display in your list view.
Also see my answer heres:
Firebase query if child of child contains a value (for more explanation on why the queries won't work in your current structure, and why they won't scale in the first structure in my answer).
Best way to manage Chat channels in Firebase (for an alternative way of naming the chat rooms).
In firestore i have a collection called things.
Each thing is owned by a user.
Each thing can be shared by the owner with other specified users.
the structure of thing looks something like
{
id: "thing01",
sharedWith: {
"user1": true,
"user2": true,
},
dtCreated: 3458973948
}
When I want to retrieve all thing objects that are shared with user1, ordered by dtCreated desc,
i can't do this without having to create an index on things.thing.user1
i.e. for every unique userid i have to create an index on the things collection.
Obviously this is not practical. The docs talk about using full text search for this, but this doesn't seem like a problem we would want to use full text search for.
Is there a different way i should be structuring the data to achieve what i want?
Is firestore just the wrong technology choice for this?
It's working very well for storing the thing objects themselves.
---- update ----
this question is not a real duplicate of Firestore: Working with nested single queries because the answer provided there is very specific to the OP's context.
In my application 2 collections are there.
1.profile - Fields are : username,id,city and postalcode
2.material - id,version,descrption and usage
In single collection we use as shown below :
var query = {};
query.username = 'xxxx';
query.city= 'yyyy';
Need Multiple Collections Query as shown below data?
Need query for to pass username and city in profile and descrption in material?
MongoDB does not support joins in the way a relational DB (e.g., MySQL) does. There are a number of materials available on the subject, principally...
Discover Meteor's tutorial on reactive joins
Reactive and Non-Reactive Join with MongoDB
This HackPad about reactive join packages
What these all boil down to is this: It's not native in MongoDB, but with Meteor, you have three options:
Use a package to do it for you
De-normalize (include one collection entirely within the other)
Do it yourself with publication and routing
From your comment:
In Profile Id is there and material are also id there.So these two are same
it sounds like the id fields are what you'd like to join by -- the second option (de-normalize) here is really easy, if you can get away with it. Rather than having two Collections, have one Collection in the following format:
{
username,
material: {
version,
description,
usage
},
city,
postalcode
}
and then query like so:
Profiles.find({username: 'xxxx', city: 'yyyy', "material.description": "zzzz"});
This has obvious tradeoffs in terms of storage efficiency and re-usability (for instance, if your material Collection is used elsewhere, you can't really just embed it in the profile Collection). Note that this also works if you have many materials that have the same description.
If you need to keep them separate, you can narrow down the set of fields to look in manually (option 3) -- you can see how I did that on this MeteorPad, but the basic idea is in your publish function, query one Collection first, then use that information to query the other:
// Return all profiles with a certain material description -- includes multiple materials.
Meteor.publish('profiles', function(username, city, material) {
var materialIds = Materials.find({description: material}).map(function(mat) { return mat._id });
return Profiles.find({material: {$in: materialIds}, username: username, city: city});
});
There are a lot of choices for packages, so I will leave it up to you to find the one most suited to your needs and read the documentation if that's the route you choose.