Filter query posts by the count of metas for a meta key

Question

I know it is possible to filter queries to order posts by the numeric value of a meta. For example, I store the number of total likes for a post in a single meta key :

            $query->set('meta_key', 'total_likes' );
            $query->set('orderby','meta_value_num');
            $query->set('order', 'DESC');

But I would like to filter my query to order posts by the recently viewed items.
To achieve this, I store the time the item was liked in another meta key, which is not single. Each time a 'time_liked' meta is added, I check the other ones to remove those which are too old.

Does something like this exists; or how can I achieve it ?

            $query->set('meta_key', 'time_liked' );
            $query->set('orderby', ...); //something like meta_count ?
            $query->set('order', 'DESC');

Answer 1

Finally found out using two (single) posts metas :

• likes_log where I keep up to date an array where each entry is the time the item was liked. Entries are removed if they are too old (here, >1 month)

• likes_log_count where I update the number of entries in the previous log.

  function update_likes_monthly_count(){
  
      if ( get_post_status($this->post_id) != 'publish') return;
  
      $log = array();
      $time = current_time( 'timestamp' );
      $time_remove = strtotime('-1 month',$time); 
  
      if ($existing_log = get_post_meta($this->post_id, 'likes_log', true)){ //get month log
          $log = $existing_log;
      }
  
      //remove entries that are too old from log metas (multiple)
      foreach ((array)$log as $key=>$log_time){
          if ($log_time <= $time_remove){
              unset($log[$key]);
          }
      }
  
      //update log
      $log[] = $time;
      update_post_meta($this->post_id, 'likes_log', $log);
  
      //update likes count
      $count = count($log);
      return update_post_meta($this->post_id, 'likes_log_count', $count );
  }
  

then, I can use 'likes_log_count to filter my query !

        $query->set('meta_key', 'likes_log_count' );
        $query->set('orderby','meta_value_num');
        $query->set('order', 'DESC');