Must-use test file for Trac 56933.

mu-test.php

<?php

add_action( 'loop_start', 'test_56933', 12 );
// For testing https://core.trac.wordpress.org/ticket/56933.
function test_56933() {
	global $wpdb;

	$search_string = 'hello';

	$sql = $wpdb->prepare("(select $wpdb->posts.ID, post_title, {$wpdb->prefix}mgmlp_folders.folder_id, pm.meta_value as attached_file, 'a' as item_type 
from $wpdb->posts
LEFT JOIN {$wpdb->prefix}mgmlp_folders ON($wpdb->posts.ID = {$wpdb->prefix}mgmlp_folders.post_id)
LEFT JOIN $wpdb->postmeta AS pm ON (pm.post_id = $wpdb->posts.ID)
LEFT JOIN $wpdb->users AS us ON ($wpdb->posts.post_author = us.ID) 
where post_type = 'mgmlp_media_folder' and pm.meta_key = '_wp_attached_file' and SUBSTRING_INDEX(pm.meta_value, '/', -1) like '%%%s%%')
union all
(select $wpdb->posts.ID, post_title, {$wpdb->prefix}mgmlp_folders.folder_id, pm.meta_value as attached_file, 'b' as item_type
from $wpdb->posts 
LEFT JOIN {$wpdb->prefix}mgmlp_folders ON( $wpdb->posts.ID = {$wpdb->prefix}mgmlp_folders.post_id) 
LEFT JOIN $wpdb->postmeta AS pm ON (pm.post_id = $wpdb->posts.ID) 
LEFT JOIN $wpdb->users AS us ON ($wpdb->posts.post_author = us.ID) 
where post_type = 'attachment' and pm.meta_key = '_wp_attached_file' and SUBSTRING_INDEX(pm.meta_value, '/', -1) like '%%%s%%') order by attached_file", $search_string, $search_string);

	echo "<pre>";
	echo $sql;
	echo "</pre>";
	exit;
}