发生此错误可能是因为在重写post子句时未检查post类型。

筛选器回调需要第二个参数，即WP_Query 实例，然后使用它检查post_type 是你需要的。如果不进行检查，您将覆盖网站在这些WooCommerce页面上发布的任何类型的帖子的每个数据库查询。

请尝试使用此已编辑的代码，并在其中检查我的注释：

class iWC_Orderby_Stock_Status
{

    public function __construct()
    {
        // Check if WooCommerce is active
        if ( in_array( \'woocommerce/woocommerce.php\', apply_filters( \'active_plugins\', get_option( \'active_plugins\' ) ) ) ) {
            // Added the fourth parameter 2 for the number of parameters to pass to the callback method
            add_filter( \'posts_clauses\', [ $this, \'order_by_stock_status\' ], 2000, 2 );
        }
    }

    /**
     * @param string[]  $posts_clauses
     * @param \\WP_Query $query
     *
     * @return string[]
     */
    public function order_by_stock_status( $posts_clauses, $query )
    {
        // Bail early if the post_type is not what we need
        if ( $query->get( \'post_type\' ) !== \'product\' ) {
            return $posts_clauses;
        }

        global $wpdb;
        // only change query on WooCommerce loops
        if ( is_woocommerce() && ( is_shop() || is_product_category() || is_product_tag() ) ) {
            $posts_clauses[\'join\'] .= " INNER JOIN $wpdb->postmeta istockstatus ON ($wpdb->posts.ID = istockstatus.post_id) ";
            $posts_clauses[\'orderby\'] = " istockstatus.meta_value ASC, " . $posts_clauses[\'orderby\'];
            $posts_clauses[\'where\'] = " AND istockstatus.meta_key = \'_stock_status\' AND istockstatus.meta_value <> \'\' " . $posts_clauses[\'where\'];
        }

        return $posts_clauses;
    }
}

new iWC_Orderby_Stock_Status;