How to query on ref in Faunadb? - faunadb

Question

I have data like this
{
"ref": Ref(Collection("categories"), "1"),
"data": {
"title": "Game"
}
}
And
[
{
"ref": Ref(Collection("courses"), "1"),
"data": {
"categoryRef": Ref(Collection("categories"), "1"),
"courseTitle": "101",
"description": "Some1"
}
},
{
"ref": Ref(Collection("courses"), "2"),
"data": {
"categoryRef": Ref(Collection("categories"), "1"),
"courseTitle": "102",
"description": "Some2"
}
},
{
"ref": Ref(Collection("courses"), "3"),
"data": {
"categoryRef": Ref(Collection("categories"), "2"),
"courseTitle": "103",
"description": "Some3"
}
}
]
I just want to get all courses that belong to the selected category, in this case game
So result will be these.
[
{
"ref": Ref(Collection("courses"), "1"),
"data": {
"categoryRef": Ref(Collection("categories"), "1"),
"courseTitle": "101",
"description": "Some1"
}
},
{
"ref": Ref(Collection("courses"), "2"),
"data": {
"categoryRef": Ref(Collection("categories"), "1"),
"courseTitle": "102",
"description": "Some2"
}
}
]
Is this just a simple index on categoryRef and search in it? should I pass ref as FQL like this? q.Ref(q.Collection('categories'), '1')
Or maybe something like this which I don't know how to finish it.
q.Map(
q.Paginate(q.Documents(q.Collection('courses'))),
q.Lambda('courseDoc',
q.Let({
course: q.Get(q.Var('courseDoc')),
categoryRef: q.Get(q.Select(['data', 'categoryRef'], q.Var('course'))),

Answer 1

You need an index to perform searching on collections of arbitrary size. Only small collections are amenable to the "table scan" approach.
If create an index, like this:
> CreateIndex({
name: "courses_by_category",
source: Collection("courses"),
terms: [
{ field: ["data", "categoryRef"] },
],
})
Then you can search for course documents with a query like this:
> Paginate(
Match(
Index("courses_by_category"),
Ref(Collection("categories"), "1")
)
)
{
data: [ Ref(Collection("courses"), "1"), Ref(Collection("courses"), "2") ]
}
To fetch the entire document for matching entries:
> Map(
Paginate(
Match(
Index("courses_by_category"),
Ref(Collection("categories"), "1")
)
),
Lambda("ref", Get(Var("ref")))
)
{
data: [
{
ref: Ref(Collection("courses"), "1"),
ts: 1663619044380000,
data: {
categoryRef: Ref(Collection("categories"), "1"),
courseTitle: '101',
description: 'Some1'
}
},
{
ref: Ref(Collection("courses"), "2"),
ts: 1663619067090000,
data: {
categoryRef: Ref(Collection("categories"), "1"),
courseTitle: '102',
description: 'Some2'
}
}
]
}