我有这个函数来获取所有帖子类型的元键。

 public function pgggo_custom_post_type_keylist()
        {
            //gets the list of post types 
            $pgggo_custompostype_array = $this->pgggo_list_of_posttypes();

            $pgggo_getposts            = array();

            foreach ($pgggo_custompostype_array as $value) {
                $args = array(
                    \'numberposts\' => 1,
                    \'post_type\'   => $value,
                );
                if (!empty(get_posts($args)[0]->ID)) {
                    $pgggo_getposts[] = get_posts($args)[0]->ID;
                }

            }
            $new_array = array();
            foreach ($pgggo_getposts as $value) {
                $new_array[] = get_post_custom($value);
            }

            $result = array();
            foreach ($new_array as $sub) {
                $result = array_merge($result, $sub);
            }
            $result     = array_keys($result);
            $result     = array_unique($result);
            $result     = array_combine($result, $result);
            $result[\'\'] = \'NONE\';
            return $result;
        }

虽然它工作得很好，但会导致高数据库查询和重复查询。是否有任何方法可以改进此解决方案或替代解决方案？

public function get_metadata_keys(){
    global $wpdb;

    $meta_query = $wpdb->get_results(
        "
        SELECT DISTINCT meta_key
        FROM {$wpdb->postmeta}
        "
    , ARRAY_A );

    $meta_keys = wp_list_pluck( $meta_query, \'meta_key\' );
    return $meta_keys;
}