Firebase Firestore - OR query alternative

Question

In this question Firebase Firestore - OR query they said there is no OR query. This means I can\'t easily query for items that have an ID that is in an array I got earlier.

Answer 1

You could combine the Observables using rxjs;

orQuery(){

    const $one = this.afs.collection("items", ref => ref.where("itemId","==","1")).valueChanges();
    const $two = this.afs.collection("items", ref => ref.where("itemId","==","3")).valueChanges();

    return combineLatest($one,$two).pipe(
        map(([one, two]) => [...one, ...two])
    )
}

getOr(){
    this.orQuery().subscribe(data => console.log(data))
}

Answer 2

This seems like a good case for duplicating some of the item data. I assume that some item properties like "name" are immutable and can therefore be stored in the PurchasedItems subcollection without worrying about future updates.

So if you add some of the data to PurchasedItems:

Users/uid/PurchasedItems/itemid

    // Existing 
    payedInMoney: "$0.00"
    payedInCoins: "100"
    itemId: "itemid"
    timeStamp: timestamp

    // Add these
    name: "Item Name"
    url: "http://foo.bar/123"

Then you will have enough information to display the list of a user's purchased items in a single query without needing to also look up each item by ID.