Nested query in Firebase Firestore - firebase

Question

I have a Firestore database structure like this:
(Articles is a collection, everything inside is arrays)
Articles:
[
{
"id": 1,
"reports": [
{
"locations": [
{
"location": "Sydney",
"country": "Australia"
},
{
"location": "Perth",
"country": "Australia"
}
],
},
{
"locations": [
{
"location": "King County, Washington",
"country": "USA"
}
],
}
]
},
{
"id": 2,
"reports": [
{
"locations": [
{
"location": "Brisbane",
"country": "Australia"
}
]
}
]
}
]
I'd like to create a query to return all Articles that mention a specific country.
Am I better off restructuring my database?

Answer 1

While Firestore's array-contains queries can get you close to this, you can't use them in your current data model as you're nesting arrays.
To allow the use-case you'll at the very least need to unnest one of those arrays into a subcollection of each article, so:
Articles (collection)
$article
reports (collection)
$report (document with a locations array)
At that point you can use a collection group query to search all reports collections, and then array-contains to find the relevant report documents:
var ref = firebase.firestore().collectionGroup("reports");
ref.where("locations", "array-contains", { location: "Sydney", country: "Australia" })
Never mind the below answer, which assumed you had only one level of array...
This type of query should be possible, as far as I can see, using the array-contains operator. Keeping in mind that you need to specify the entire array item.
So something like:
collectionRef.where("reports.locations", "array-contains",
{ location: "Sydney", country: "Australia" })