We have a collection called customer that has all the details and another collection called merchant with a sub-sub-collection called merchant customers where we are paginating the customers.
We need to search the customer using the main customer document fields with pagination using the reference from merchant sub-collection.
Customer Main records
Sub-Sub-collection
Firestore queries can only filter (and thus also only paginate) on values that are present in the documents that it returns. There is no way to filer a document on values from somewhere else in the database.
So to allow the use-case, you will either have to replicate the relevant information from the subcollection into the main customer document, or replicate the information from the main customer document into the documents in the subcollection and then query that.
Related
I have a firestore DB where I'm storing polls in one collection and responses to polls in another collection. I want to get a document from the poll collection that isn't referenced in the responses collection for a particular user.
The naive approach would be to get all of the poll documents and all of the responses filtered by user ID then filter the polls on the client side. The problem is that there may be quite a few polls and responses so those queries would have to pull down a lot of data.
So my question is, is there a way to structure my data so that I can query for polls that haven't been completed by a user without having to pull down the collections in their entirety? Or more generally, is there some pattern to use when you need to query for documents in one collection that aren't referenced by another?
The documents in each of the collections look something like this:
Polls:
{
question: string;
answers: Answer[];
}
Responses:
{
userId: string;
pollId: string;
answerId: string;
}
Anyhelp would be much appreciated!
Queries in Firestore can only return documents from one collection (or from all collections with the same name) and can only contain conditions on the data that they actually return.
Since there's no way to filter based on a condition in some other documents, you'll need to include the information that you want to filter on in the polls documents.
For example, you could include a completionCount field in each poll document, that you initially set to 0, and then update only every poll completion. With that in place, the query becomes a simple query on the completionCount field of the polls collection.
For a specific user I'd actually add all polls to their profile document, and remove them from there. Duplicating data is usually the easiest (and sometimes only) way to implement use-cases such as this.
If you're worried about having to add each new poll to each new user profile when it is created, you can also query all polls on their creation timestamp when you next load a user profile and perform that sync at that moment.
load user profile,
check when they were last active,
query for new polls,
add them to user profile.
I'm currently working on an application where users can create groups and invite others in it.
I would like people in the same group to be able to see their first and last names.
To do that, I have a collection named Users where each of the users have a document contains all their personnal data, like first and last names, phone, position , ...
I have also another collection named Groups, where all of my groups are stored, with their name, and an array contaning the ID of the members.
When an user open the app, a first request is done for request his groups (he recieve the groups names and the arrays of members). After, if he want to know the user in a certain group, another request is done for search only the first and last name of all the members.
So, I imagine that there is a query that will return me only the fields that I would like to retrieve, and that there is a rule allowing a potential hacker to be refused access to the entire user document except if the user is the owner of the document.
// For retrieving my user's groups
Stream<List<Group>?> get organizations {
return firestore
.collection('Groups')
.where('members', arrayContains: this.uid)
.snapshots()
.map(_groupsFromSnapshot);
}
// For retrieving names of the members of a group
Stream<List<Member>?> getMembers(Group group){
return firestore
.collection('Users')
// and i dont know what to do here ...
}
With the Client SDKs and the Flutter plugin it is not possible to get only a subset of the fields of a Document. When you fetch a Document you get it with all its fields.
If you want to get only a subset of the fields of a document, you can implements the two following approaches:
Denormalize your data: You create another collection which contains documents that only contain the fields you want to expose. You need to synchronize the two collections (the Users collection, which is the "master", and the new collection): for that it's quite common to use a Cloud Function. Note also that it's a good idea to use the same documentID for the linked documents in the two collections.
Use the Firestore REST API to fetch the data: With the REST API you can use a DocumentMask when you fetch one document with the get method or a Projection when you query a Collection. The DocumentMask or the Projection will "restrict a get operation on a document to a subset of its fields". You can use the http package for calling the API from your Flutter app.
HOWEVER, the second approach is not valid if you want to protect the other users data: a malicious user could call the Firestore REST API with the same request but without a DocumentMask or a Projection. In other words, this approach is interesting if you just want to minimize the network traffic, not if you want to keep secret certain fields of a document.
So, for your specific use case, you need to go for the first solution.
I have a collection of "quizes" that users will participate in. When a user takes a quiz I create a document in "results" collection for with that userId and quizId. I want my app to pull all docs from "quizes" collection excluding the ones that the user taken. In SQL I would do "NOT IN" clause and accomplish that, but I have no idea how to best approach this in Firestore.
There's no equivalent query in Firestore. You would need to pull all the data and determine which docs are relevant on clientside.
Alternatively, you can create a list of all quizzes for each user and maintain this list. You could add and remove quizzes for each user as they become relevant/irrelevant to show them.
I have a collection in mongodb that stores activities of customers like product_view, added_to_cart etc with productId. I need this data to display products to my customer when he visits next.
Right now I am thinking to store all data of a customer in a single document,such as with customer_id as key and corresponding activities in array like product_view activities in product_view array etc.This will be fast to fetch for me as all data of a customer will be in one key only, but my consideration is that data size will go on increasing always this way. Moreover I may need to check say last 50-100 activities of a customer only. For that too I need to fetch the entire document.
What will be the best way to store this data. Request for data will be very very frequent. How can I manage response time ?
Your question answers itself. Have customer activity as separate collection with reference to customerId. Any time customer visits, you know customerId, hence can apply filter/aggregate operations to get whatever you want.
This way you can do paginated fetch of customer activities.
I have two collections - Tickets and Users. Where a user can have one to many tickets. The ticket collection is defined as follows
Ticket = {_id, ownerId, profile: {name}}
The ownerId is used to find all tickets that belong to a specific person. I need to write a query that gets me all users with no tickets.
How can i write this query without having to loop through all users, checking if the userID shows up in any Tickets?
Would a bidirectional storage cause me any performance problems ? For example, if i were to change my users collection and add an array of tickets: [ticketID, ticketID2, ...]?
I'd go with the array of tickets being stored in users. As far as I know, Mongo doesn't really have a way to query one collection based on the (lack of) elements in another collection. With the array, though, you can simply do db.users.find({tickets:[]}).