change posts_orderby of the callback wp_query?

Question

I found this answer that helps with ordering query results by the post type in my search query. But the issue is that it helps when I go to

https://example.com/?s=query%20string

that is if I search using native php search. And that's great. But I also have the search via ajax - when I type, the ajax will call my callback function that is registered on a custom rest endpoint.

So I am wondering if there is any way that I can identify that custom query so that I can reuse that filter? In the conditional:

if ( ! is_admin() && is_search() && is_my_custom_search_query() ) { 

The alternative is to try to rewrite the CASE orderby to WP_Query which I am not sure is possible tbh.

Search query for ajax looks like:

  $query_string   = sanitize_text_field( wp_unslash( $_GET['searchString'] ) );
  $page_no        = intval( $_GET['pageNo'] );
  $posts_per_page = 9;
  $offset         = ( $page_no - 1 ) * $posts_per_page;

  $search_args = array(
      'posts_per_page' => $posts_per_page,
      'post_status'    => 'publish',
      'perm'           => 'readable',
      's'              => $query_string,
      'offset'         => $offset,
  );

  $search_results = new WP_Query( $search_args );

Answer 1

Ok, found the answer! I added 'query_id'parameter in my query

$query_string   = sanitize_text_field( wp_unslash( $_GET['searchString'] ) );
$page_no        = intval( $_GET['pageNo'] );
$posts_per_page = 9;
$offset         = ( $page_no - 1 ) * $posts_per_page;

$search_args = array(
    'posts_per_page' => $posts_per_page,
    'post_status'    => 'publish',
    'perm'           => 'readable',
    's'              => $query_string,
    'offset'         => $offset,
    'query_id'       => 'my_custom_ajax_search',
);

$search_results = new WP_Query( $search_args );

After that in my filter

add_filter( 'posts_orderby', 'my_order_search_by_posttype', 10, 2 );

function my_order_search_by_posttype( $orderby, $wp_query ) {
    if ( ! is_admin() && ( is_search() || isset( $wp_query->query['query_id'] ) && $wp_query->query['query_id'] === 'my_custom_ajax_search' ) ) {
...
    }
}

And it works! :)