Remove duplicates in an object in JSONiq

Question

This is an example object that I got:

{ "query1" : [ { "name" : "John", "id" : 1234 }, { "name" : "Rose", "id" : 3214 }, { "name" : "John", "id" : 1234 } ] }

How can I remove the duplicates using group by and array navigation / unboxing?

I tried implementing the group by clause after the where clause but did not get the correct answer

Answer 1

In JSONiq, you can indeed remove duplicates with a group by and array unboxing, like so:

let $data := {
  "query1" : [
    { "name" : "John", "id" : 1234 },
    { "name" : "Rose", "id" : 3214 },
    { "name" : "John", "id" : 1234 }
  ]
}
return {
 "query1" : [
    for $obj in $data.query1[]
    group by $n := $obj.name, $i := $obj.id
    return $obj[1]
  ]
}

There is also a generic approach that will work even with unknown fields and more nested values:

let $data := {
  "query1" : [
    { "name" : "John", "id" : 1234 },
    { "name" : "Rose", "id" : 3214 },
    { "name" : "John", "id" : 1234 }
  ]
}
return {
  "query1" : [
    for $obj at $i in $data.query1[]
    where
      every $other in $data.query1[][position() lt $i]
      satisfies not deep-equal($obj, $other)
    return $obj
  ]
}