so here i have
So I am making dating app, and now i come to the moment, where i need to create a list of people to match with for user.
So I need a firebase query to look in to gender and check if the people already matched, if yes it should not be included in the list.
I tried, filtering data by gender. How I should edit this query to check if they already matched?
Matches are displayed in users/{userID}/matches/{matchedUserID}
This is what i tried:
async createUserListAndNavigate() {
let genderTolook = 'female';
let data = firebase
.database()
.ref('users/')
.orderByChild('gender')
.equalTo(genderTolook);
data.once('value', snapshot => {
console.log(JSON.stringify(snapshot.val()));
});
}
You can use the array-contains-any query to check if the matches array already contains the user_id.
var users = db.collection("users");
users.where('tempuser.matches', 'array-contains-any', [<USER_ID_TO_MATCH>]);
Based on the result you can make further queries/operations. You could also combine this query with other queries.
See the documentation for further details.
Related
I'm working on a Flutter app where each user can create projects, and share projects with other users. I've created a 'shares' collection, where each user's ID is a document, and within that document, all project IDs that have been shared with that user are collected like so, with a boolean that represents whether or not the share has been accepted yet:
Next, I created a collection of the projects themselves, like so:
Now, I'd like to query the 'projects' collection and return only the projects that are in a given user's 'shares' list. First off, how can I get each document in the share list's ID? And secondly, is it possible to compare that ID to the contents of a List using a .where() clause?
I've been trying something like this, but to no avail:
Stream<List<Map<String, dynamic>>> getListOfProjectsForUser({#required List<String> shares}) {
var ref = _firestore.collection('projects');
return ref
.where(shares, arrayContains: ref.id)
.snapshots()
.map((QuerySnapshot snapshot) => snapshot.docs.map((DocumentSnapshot doc) => doc.data()).toList());
}
I also tried this:
Stream<List<Map<String, dynamic>>> getListOfProjectsForUser({#required List<String> shares}) {
var ref = _firestore.collection('projects');
return ref
.where(shares, arrayContains: FieldPath.documentId)
.snapshots()
.map((QuerySnapshot snapshot) => snapshot.docs.map((DocumentSnapshot doc) => doc.data()).toList());
}
Is what I'm trying to do even possible? I've been messing with this for two days and my head's exploding. Any help would be greatly appreciated. Thanks in advance.
You'll need two operations.
Read the document for the user, to determine the list of project IDs.
Perform a in query for the project documents matching those IDs. The in operator accepts up to 10 IDs, so if you have more than 10 projects you'll need multiple queries and merge the results in your application code.
var citiesRef = db.collection("projects");
citiesRef.where(FieldPath.documentId, arrayContains: ['project1id', 'project2id']);
Also see:
The FlutterFire documentation for the where(field, whereIn:) operation
The FlutterFire documentation for the FieldPath.documentId field
First off, how can I get each document in the share list's ID?
For this, you're required to actually query the entire collection. You can iterate the results to collect the IDs of each document. There is no easy way to just get a list of IDs directly from web and mobile client code. See: How to get a list of document IDs in a collection Cloud Firestore?
And secondly, is it possible to compare that ID to the contents of a List using a .where() clause?
If you have a list of document ID strings in memory that could be any length, you will need to perform a query filtering projects for "projOwner" for each individual ID. There are no SQL-like joins in Firestore, so you can't simply join the two collections together with a single query.
Here's how you do a single one - you have to call out the name of the field to filter on:
firestore
.collection("projects")
.where("projOwner", isEqualTo: id)
If you have 10 or less share IDs in the list, you can use an "in" query to find matches from projects, and it will not work with any more.
firestore
.collection("projects")
.where("projOwner", whereIn: listOfIds)
So, if you think the list could ever be larger than 10, you should just start by performing individual queries for each share ID.
if 'arrayContains' is not working try 'whereIn'.
var citiesRef = db.collection("projects");
citiesRef.where(FieldPath.documentId, whereIn: ['project1id',
'project2id']);
I am trying to fetch all documents whose sub-collection contain a specific document ID. Is there any way to do this?
For example, if the boxed document under 'enquiries' sub-collection exists, then I need the boxed document ID from 'books' collection. I couldn't figure out how to go backwards to get the parent document ID.
I make the assumption that all the sub-collections have the same name, i.e. enquiries. Then, you could do as follows:
Add a field docId in your enquiries document that contains the document ID.
Execute a Collection Group query in order to get all the documents with the desired docId value (Firestore.instance.collectionGroup("enquiries").where("docId", isEqualTo: "ykXB...").getDocuments()).
Then, you loop over the results of the query and for each DocumentReference you call twice the parent() methods (first time you will get the CollectionReference and second time you will get the DocumentReference of the parent document).
You just have to use the id property and you are done.
Try the following:
Firestore.instance.collection("books").where("author", isEqualTo: "Arumugam").getDocuments().then((value) {
value.documents.forEach((result) {
var id = result.documentID;
Firestore.instance.collection("books").document(id).collection("enquiries").getDocuments().then((querySnapshot) {
querySnapshot.documents.forEach((result) {
print(result.data);
});
First you need to retrieve the id under the books collection, to be able to do that you have to do a query for example where("author", isEqualTo: "Arumugam"). After retrieving the id you can then do a query to retrieve the documents inside the collection enquiries
For example, if the boxed document under 'enquiries' sub-collection exists, then I need the boxed document ID from 'books' collection.
There is no way you can do that in a single go.
I couldn't figure out how to go backwards to get the parent document ID.
There is no going back in Firestore as you probably were thinking. In Firebase Realtime Database we have a method named getParent(), which does exactly what you want but in Firestore we don't.
Queries in Firestore are shallow, meaning that it only get items from the collection that the query is run against. Firestore doesn't support queries across different collections in one go. A single query may only use the properties of documents in a single collection. So the solution to solving your problem is to perform two get() calls. The first one would be to check that document for existence in the enquiries subcollection, and if it exists, simply create another get() call to get the document from the books collection.
Renaud Tarnec's answer is great for fetching the IDs of the relevant books.
If you need to fetch more than the ID, there is a trick you could use in some scenarios. I imagine your goal is to show some sort of an index of all books associated with a particular enquiry ID. If the data you'd like to show in that index is not too long (can be serialized in less than 1500 bytes) and if it is not changing frequently, you could try to use the document ID as the placeholder for that data.
For example, let's say you wanted to display a list of book titles and authors corresponding to some enquiryId. You could create the book ID in the collection with something like so:
// Assuming admin SDK
const bookId = nanoid();
const author = 'Brandon Sanderson';
const title = 'Mistborn: The Final Empire';
// If title + author are not unique, you could add the bookId to the array
const uniquePayloadKey = Buffer.from(JSON.stringify([author, title])).toString('base64url');
booksColRef.doc(uniquePayloadKey).set({ bookId })
booksColRef.doc(uniquePayloadKey).collection('enquiries').doc(enquiryId).set({ enquiryId })
Then, after running the collection group query per Renaud Tarnec's answer, you could extract that serialized information with a regexp on the path, and deserialize. E.g.:
// Assuming Web 9 SDK
const books = query(collectionGroup(db, 'enquiries'), where('enquiryId', '==', enquiryId));
return getDocs(books).then(snapshot => {
const data = []
snapshot.forEach(doc => {
const payload = doc.ref.path.match(/books\/(.*)\/enquiries/)[1];
const [author, title] = JSON.parse(atob(details));
data.push({ author, title })
});
return data;
});
The "store payload in ID" trick can be used only to present some basic information for your child-driven search results. If your book document has a lot of information you'd like to display once the user clicks on one of the books returned by the enquiry, you may want to store this in separate documents whose IDs are the real bookIds. The bookId field added under the unique payload key allows such lookups when necessary.
You can reuse the same data structure for returning book results from different starting points, not just enquiries, without duplicating this structure. If you stored many authors per book, for example, you could add an authors sub-collection to search by. As long as the information you want to display in the resulting index page is the same and can be serialized within the 1500-byte limit, you should be good.
The (quite substantial) downside of this approach is that it is not possible to rename document IDs in Firestore. If some of the details in the payload change (e.g. an admin fixes a book titles), you will need to create all the sub-collections under it and delete the old data. This can be quite costly - at least 1 read, 1 write, and 1 delete for every document in every sub-collection. So keep in mind it may not be pragmatic for fast changing data.
The 1500-byte limit for key names is documented in Usage and Limits.
If you are concerned about potential hotspots this can generate per Best Practices for Cloud Firestore, I imagine that adding the bookId as a prefix to the uniquePayloadKey (with a delimiter that allows you to throw it away) would do the trick - but I am not certain.
I'm working on a React Native application and I'm fetching profiles from a firebase collection.
And I want to add a search functionality where when I enter even the first 1 or 2 (or more) alphabets of a username and press the search button.
I should be able to fetch usernames starting with those 1 or 2 alphabets.
I did check Cloud Firestore queries but couldn't find one for my problem.
UPDATED QUESTION:
In the above code, I'm adding the below code as answered by Renaud Tarnec.
let queries = hashes.map(hash => rangeQueryParams(hash))
.map(range => profiles.where('hash', '>=', range.start).where('hash', '<', range.end)
.orderBy('displayName') // displayName is the name of Field here
.startAt(searchString)
.endAt(searchString + '\uf8ff')
.get());
But this doesn't seems to work. I guess it's because range filter and orderBy are on different fields here.
You should use a combination of orderBy(), startAt() and endAt(), see the documentation here: https://firebase.google.com/docs/firestore/query-data/order-limit-data?authuser=0
var searchString = 'Sh' //Example of value
firebase
.firestore()
.collection('yourCollectioName')
.orderBy('username')
.startAt(searchString)
.endAt(searchString + '\uf8ff')
.get()
.then(...)
The character \uf8ff used in the query is after most regular characters in Unicode, therefore the query matches all values that start with searchString.
An approach for full text search recommended by Firebase is to use Algolia https://firebase.google.com/docs/firestore/solutions/search
Using Firestore’s queries with start at and end at with an ordered collection certainly work. If you have a need for full text search within your app elsewhere that requires spelling tolerance etc for example then moving to Algolia is worth considering instead of using compound firestore queries
I'm running into an issue with Firestore that is pretty unintuitive to me and so I'm wondering if anyone can help me understand why Firestore is giving this result.
Let's say I have a collection called "people" with fields "firstName" and "lastName". Let's say I have 20 documents in that collection that have the lastName "Quaid". I then have a field "inCanada" that is only present in a subset of those 20 documents, let's say 5. The other 15 documents don't have that field.
What is surprising is that an orderBy clause using that optional field is actually filtering the result set rather than just sorting it, which doesn't make sense to me when compared with other databases.
In the below example, I expected both result sets to have 20 elements, however the second set that has the orderBy only has those 5 documents where that field is present.
Could someone please explain why Firestore does this?
const Admin = require('firebase-admin');
(async function () {
const initFirebase = require('../initFirebase');
initFirebase();
const people = Admin.firestore().collection('people');
const quaids = people.where('lastName', '==', 'Quaid')
const quaids1 = await quaids.get();
const quaids2 = await quaids.orderBy('inCanada', 'desc').get();
console.log(quaids1._size); // 20
console.log(quaids2._size); // 5
})();
In a nutshell, this is because Firestore queries are based on indexes: each time you create a doc Firestore creates an index for each field of the doc.
So since the field "inCanada" is only present "in a subset of the 20 documents", only this subset of documents is present in the "inCanada" index, resulting in the situation you mention.
This official video from Todd Kerpelman from the Firebase team explains it very well: https://www.youtube.com/watch?v=Ofux_4c94FI#t=4m17s. (This link will open the video at 4m17s i.e. when the explanations on the index mechanism start. However the part on the impact of indexes on the querying possibilities is more around 6m22s!)
If you want to include the other documents in your query results you should write a value for the field "inCanada" for those documents, for example use a false value (and use true for the docs that are "inCanada").
Using firebase and Swift. Is there any way of comparing the current user:
'let uid = Auth.auth().currentUser?.uid'
with the autogenerated id's under 'Users' or 'Advertiser' in the Firebase Structure?
I want to do a If statement and see if the currentUser matches with the Id's under Advertiser or Users.
If you're trying to check if a certain node exists in the database, that should be a fairly simple with something like:
Database.database().reference(withPath: "Advertiser").child(uid)
.observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.exists() ...
Also see:
Swift Firebase Check if user exists