How to structure a search list in Firestore? - ios

Question

I want to show a list of artists in my app which the user will be able to search through. I'm not sure however how to save this in Firestore?
First I created a collection "searchLists" with a document for each DJ but that means a lot of document reads so that's out of the question.
Now I created a document called "artists" which has a field "artistsDictionary" which contains all the artists.
| searchLists (collection)
* artists (document)
- artistsArray (array)
0: (map)
name: "Artist 0" (string)
1: (map)
name: "Artist 1" (string)
2: (map)
name: "Artist 2" (string)
And I retrieve and parse the array as followed:
let docRef = db.collection("searchLists").document("artists")
docRef.getDocument { (document, error) in
if let document = document, document.exists {
guard let documentData = document.data() else { return }
let artistsDictionaryArray = documentData["artistsArray"] as? [[String: Any]] ?? []
let parsedArtists = artistsDictionaryArray.compactMap {
return SimpleArtist(dictionary: $0)
}
self.artistsArray = parsedArtists
} else {
print("Document does not exist")
}
}
(SimpleArtist is a struct containing a "name" field.)
And I mean, it works, but I'm still new to Firestore and this seems kinda off. Is it? Or is this how I should/could do it?

Answer 1

First I created a collection "searchLists" with a document for each DJ but that means a lot of document reads so that's out of the question.
This is the right approach, so you should go ahead with it.
Why do I say that?
According to the official documentation regarding modeling data in a Cloud Firestore database:
Cloud Firestore is optimized for storing large collections of small documents.
Storing data in an array is not a bad option but this is most likely used, let's say to store favorite djs. I say that because the documents have limits in Firestore. So there are some limits when it comes to how much data you can put into a document. According to the official documentation regarding usage and limits:
Maximum size for a document: 1 MiB (1,048,576 bytes)
As you can see, you are limited to 1 MiB total of data in a single document. When we are talking about storing text, you can store pretty much but as your array getts bigger, be careful about this limitation.

Answer 2

First off, Alexs' answer is 100% correct.
I want to add some additional data points that may help you in the long run.
The first item is arrays. Arrays are very challenging in NoSQL databases - while they provide a logical sequence data via the index, 0, 1, 2 they don't behave like an array in code - so for example; Suppose you wanted to insert an item at an index. Well - you can't (*you can but it's not just a simple 'insert' call). Also, you can't target array elements in queries which limits their usefulness. The smallest unit of change in a Firestore array field is the entire field - smaller changes to individual elements of a field can't be made. The fix is to not use arrays and to let FireStore create the documentID's for you data 'objects' on the fly e.g. the 'keys' to the node
The second issue - (which may not be an issue currently) is how the data is being handled. Suppose you release your app and a user has 2 million artists in their collection - with your code as is, all of that data is downloaded at one time which will probably not be the best UI experience but additionally, it could overwhelm the memory of the device. So working in 'chunks' of data it a lot easier on the device, and the user.
So I put together some sample code to help with that.
First a class to store your Artist data in. Just keeps track of the documentID and the artist name.
class ArtistClass {
var docId = ""
var name = ""
init(aDocId: String, aName: String) {
self.docId = aDocId
self.name = aName
}
}
and a class array to keep the artists in. This would be a potential dataSource for a tableView
var artistArray = [ArtistClass]()
This is to write an artist as a document instead of in an array. The documentID is a FireStore generated 'key' that's created for each artist.
func writeArtists() {
let artistsRef = self.db.collection("artists")
let floyd = [
"name": "Pink Floyd"
]
let zep = [
"name": "Led Zeppelin"
]
let who = [
"name": "The Who"
]
artistsRef.addDocument(data: floyd)
artistsRef.addDocument(data: zep)
artistsRef.addDocument(data: who)
}
and then function to read in all artists.
func readArtists() {
let artistsRef = self.db.collection("artists")
artistsRef.getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
let docId = document.documentID
let name = document.get("name") as! String
let artist = ArtistClass(aDocId: docId, aName: name)
self.artistArray.append(artist)
}
for a in self.artistArray { //prints the artists to console
print(a.docId, a.name)
}
}
}
}
So your data in Firestore looks like this
artists (collection)
8lok0a0ksodPSSKS
name: "Let Zeppelin"
WKkookokopkdokas
name: "The Who"
uh99jkjekkkokoks
name: "Pink Floyd"
so then the cool part. Suppose you have a tableView that shows 10 artists at a time with a down button to see the next 10. Make this change
let artistsRef = self.db.collection("artists").order(by: "name").limit(to: 10)
Oh - and you'll notice the function of sorting now goes the server instead of the device - so if there's a million artists, it's sorted on the server before being delivered to the device which will be significantly faster.
You can also then more easily perform queries for specific artist data and you won't need to be as concerned about storage as each artist is their own document instead of all artists in one.
Hope that helps!