Order posts by date and then by custom field

Question

I am trying to do something like this one. Ordering posts by day (not time) AND meta value

I want to list blog posts ordered by date (not time) and then within that day, I want to sort them by custom field my_post_rating. This simply outputs posts ordered by rating.

$args = array(
  'post_type' => 'post',
  'posts_per_page' => '-1',
  'meta_key' => 'my_post_rating',
  'orderby' => 'meta_value_num',
  'ignore_sticky_posts' => 1,
);

$new_query = new WP_Query( $args );

I have also tried suggested solution but it did not worked. Please suggest what is wrong?

Edit // Var dump added

string(344) "SELECT wp_posts.* FROM wp_posts INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) WHERE 1=1 AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') AND (wp_postmeta.meta_key = 'my_post_rating' ) GROUP BY wp_posts.ID ORDER BY wp_postmeta.meta_value+0 DESC "

Answer 1

  add_filter('posts_orderby', 'posts_orderby');

  function posts_orderby($orderby_for_query) {
        global $wpdb;
        $prefix = $wpdb->prefix;
        $orderby_for_query = "LEFT(" . $prefix . "posts.post_date, 10) DESC, " . $orderby_for_query;
        return $orderby_for_query;
    }   

This produces this query:

SELECT   wp_posts.* FROM wp_posts  INNER JOIN wp_postmeta ON (wp_posts.ID = wp_postmeta.post_id) WHERE 1=1  AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish') AND (wp_postmeta.meta_key = 'my_post_rating' ) GROUP BY wp_posts.ID ORDER BY LEFT(wp_posts.post_date, 10) DESC, wp_postmeta.meta_value+0 DESC