解决了这个问题后，我想更新这个问题。这个问题源于以前版本的WP在上传媒体时没有包含\\u WP\\u attached\\u file meta key，而3.4现在似乎需要这样做。

下面是PHP代码，用于在数据库中循环，验证密钥和图像文件的存在，然后更新数据库。

// descend through the database
$updated = 0;
$skipped = 0;
$error = 0;
$upload_dir = wp_upload_dir();

$sql = sprintf("select * from %s where post_type = \'attachment\'", $wpdb->posts);
$all_attachments = $wpdb->get_results($sql);

foreach ($all_attachments as $attachment) {
    // get the meta value
    $meta = get_post_meta($attachment->ID, "_wp_attachment_metadata", true);
    $file = $meta[\'file\'];

    // verify that the file exists
    $file_path = $upload_dir[\'basedir\'] . \'/\' . $file;
    if (!file_exists($file_path)) {
        $error++;
    }
    else {
        // add the meta value, which returns false if it already exists
        $adding_meta = add_post_meta($attachment->ID, \'_wp_attached_file\', $file, true);
        if ($adding_meta)
            $updated++;
        else
            $skipped++;
    }
}
echo \'<div id="message" class="updated"><p>\' . sprintf("%d attachments were updated, %d were skipped and %d had errors.", $updated, $skipped, $error) . \'</p></div>\';