wordpress sort post by recent comment and new post

Based on this answered question: Ordering Wordpress posts by most recent comment

I want to sort wordpress post by recent comment and new post. I need to put this in my themes function but I always get "Page not found". Anybody can help to fix this code?

function intercept_query_clauses( $pieces ) {
global $wpdb;

$pieces['fields'] = "wp_posts.*,
  coalesce(
  (
      select max(comment_date)
      from " . $wpdb->comments ." wpc
      where wpc.comment_post_id = wp_posts.id AND wpc.comment_approved = 1
  ), 
  wp_posts.post_date 
  ) as mcomment_date
  from " . $wpdb->posts . " wp_posts
  where post_type = 'post' 
  and post_status = 'publish'";
$pieces['orderby'] = "mcomment_date desc limit 10";

return $pieces;
}
add_filter( 'posts_clauses', 'intercept_query_clauses', 20, 1 );

Any help and guide really appreciate.. Thank you.