NestedQuery: Filter _source

Elastic Stack Elasticsearch
1

Hi all!
I'm using nested mapping for my index. When I'm quering data with nested query elasticsearch returns whole _source document.

For example, nested query

{
"query": {
"nested": {
"path": "books",
"query": {
"term": {
"books.category_id": 2
}
}
}
}
}

returns matched document with source:

_source: {
id: 1,
author: me,
books: [
{
title: title1,
category_id: 1
},
{
title: title2,
category_id: 2
}
]
}

I'm interesting, can results return only with matched category_id, like

_source: {
id: 1,
author: me,
books: [
{
title: title2,
category_id: 2
}
]
}

For example, in Apache Solr it can be done with ChildTransormer.
Thanks for any help.