Get a set of unique values of all properties in a table on Hasura

I am using Hasura and have a table with the following properties:

projects: {
  country // string
  type // boolean
  year // integer
}

What I would like to do is run a query that returns all unique values of each property across all projects. So in the end I have something like:

{ country: "a", country: "b", country: "c" } (... all unique countries)
{ type: true, type: false }
{ year: 2000, year: 2001, year: 2002 } (... all unique years)

I tried the following:

query Test {
  projects(distinct_on: [country, type, year] {
    country
    type
    year
  }
}

The problem with this is though, I get duplicated values, because it takes the whole set (country, type, year) as a unique value and returns that.

Do I need to alias those requests and run each query alone to really get all unique values, or is there another way?