WordPress提高搜索结果的相关性(准确度)

//提高搜索结果相关性
if(is_search()){
add_filter('posts_orderby_request', 'search_orderby_filter');
}
function search_orderby_filter($orderby = ''){
	global $wpdb;
	$keyword = $wpdb->prepare($_REQUEST['s']);
	return "((CASE WHEN {$wpdb->posts}.post_title LIKE '%{$keyword}%' THEN 2 ELSE 0 END) + (CASE WHEN {$wpdb->posts}.post_content LIKE '%{$keyword}%' THEN 1 ELSE 0 END)) DESC,
{$wpdb->posts}.post_modified DESC, {$wpdb->posts}.ID ASC";
}