I am trying to do a collection group query from firebase firestore. But I am worried that there might be complications becauase most documents in a subcollection have the same ids as documents in other subCollections. So when I am querying all documents in collection group, I don't know if I will not run into errors or be able to distinguish between the documents.
return _fsInstance
.collectionGroup("subCollection").where('date' isEqualTo: "$date");
A single collection cannot have documents with same IDs but you can have documents with same ID in different (sub)collections. When you run your query, each document in the QuerySnapshot will have its own DocumentReference. For example:
/col/doc/(subCol1)/doc1
/col/doc/(subCol2)/doc1
Here, both subCol1 and subCol2 have document with ID doc1. The query won't cause any issues but when you read doc.id they'll be same.
Related
Is there any way to retrieve a collection along with its sub-collections from Firebase Firestore using Flutter?
fetchTestSite() async {
return await FirebaseFirestore.instance
.collection('sites')
.doc('4R3aOMBFTjumYCbETDU8')
.get()
.then((DocumentSnapshot doc) {
print('document: ${doc.data()}');
});
}
This code snippet only returns the main collection without the existing sub-collections
Is there any way to retrieve a collection along with its sub-collections from Firebase Firestore using Flutter?
No, there is no way you can do that. Queries in Firestore are shallow. This means that it can only return documents from the collection that the query is run against.
There is no way to get documents from a top-level collection and sub-collections in a single query. You can only get documents from a single collection.
However, there is a "hack" that can be made. If you want to get the data from the sub-collection that corresponds to a specific document, you can use a collectionGroup to get documents under a certain path. I explained in the following article:
How to query collections in Firestore under a certain path?
How you can do that and what limitations you might have.
If you consider at some point in time try using the Firebase Realtime Database, what you are looking for it's possible, because when you attach a listener on a specific node, you download all the data beneath it.
This is my data structure. Here are the list of users documents.
and here is the subcollection in every document.
The subcollection is containing strongly typed document which is form.
What I want is to fetch form document (not for the current user) from subcollection workerField from every users document.
what is the implementation method.
If you want to load documents from all workerField collections you can use a so-called collection group query.
So something like:
var docs = await FirebaseFirestore.instance
.collectionGroup('workerField')
.snapshots();
See my answer here for another example: Is wildcard possible in Flutter Firestore query? and more from these search results.
Cant seem to understand if arrayContains works on subCollections in Firestore.
This code does not return any data
Firestore.firestore()
.collection("all_chatrooms")
.whereField("postmoderators", arrayContains: userId)
However specifying the targeted collection path does...
Firestore.firestore()
.collection("all_chatrooms")
.document("randomId")
.collection("chatroom")
.whereField("postmoderators", arrayContains: userId)
is there a way to search for an array within subCollections without specifying a documentId?
Do you maybe have to store userIds within a map to be able to search within subColletions?
Firestore queries are shallow, meaning that when you query a specific collection "C1", only the documents from this collection are returned, and not the documents in the subcollections of the documents in "C1".
However, in your case, Collection Group queries may "come to the rescue". As indicated in the doc:
A collection group consists of all collections with the same ID. For
example, if each document in your cities collection has a
subcollection called landmarks, all of the landmarks subcollections
belong to the same collection group.
So if all the docs in the all_chatrooms collection have a subcollection named chatroom you can use a Collection Group query as follows:
Firestore.firestore().collectionGroup("chatroom").whereField("postmoderators", arrayContains: userId)
Of course, by doing so you will get ALL the docs (with userId in postmoderators) in ALL the chatroom subcollections of ALL the docs in the all_chatrooms collection.
I am querying my Firestore database as follows:
final Query roasters = Firestore.instance
.collection('retailers')
.where('retail_category', isEqualTo: 'Coffee Roasters');
I am receiving the result back of all documents in the retailers collection which have 'retail_category' set as 'Coffee Roasters'.
The Problem
I instead want to turn retail_category into a separate collection and instead reference it in the retailer field (which would negate the following reference):
"retail_categories/hEN5fzNl2hEc2tEs05Wi"
I have tried the following:
final Query roasters = Firestore.instance
.collection('retailers')
.where('retail_categories', isEqualTo: ' qretail_categories/hEN5fzNl2hEc2tEs05Wi');
Here is my Firestore configuration:
Retailers
Retail Categories
It's not possible to reference data in documents outside of the collection being used for the query. For this reason, it's very common to duplicate data between documents that need to be used in queries for each collection. If you don't want to do that, you will have to make separate queries for each referenced document.
I am trying to query subcollection in Firebase, but I always get an empty list...
This is my query:
Firestore.instance.collection('messages').where('idFrom', isEqualTo: userID).snapshots();
I know that I have subcollection with another subcollection here..
/messages/RWzG98s92mVTZniofez6YoYsNhA3-tT2Q16n1FMZoTNZQOejtWuJdCmD2/RWzG98s92mVTZniofez6YoYsNhA3-tT2Q16n1FMZoTNZQOejtWuJdCmD2/1579394957103
And my question is how to query these types of models?
Since Firstore queries are always shallow, you have to build the path to the subcollection to query.
Firestore.instance
.collection('messages')
.document(...) // ID of the nested document
.collection(...). // ID of the nested subcollection
.where('idFrom', isEqualTo: userID);
There is no way to avoid giving those nested IDs. If you can't identify the full path of the subcollection to query, you won't be able to access its documents.