我们去看看吧。如果我在dev install中获取任意附件并转储其post对象和自定义字段，我会得到以下结果：
object WP_Post (24) {
public ID -> integer 1687
public post_author -> string (1) "1"
public post_date -> string (19) "2013-09-18 14:37:07"
public post_date_gmt -> string (19) "2013-09-18 21:37:07"
public post_content -> string (0) ""
public post_title -> string (24) "dsc20050604_133440_34211"
public post_excerpt -> string (0) ""
public post_status -> string (7) "inherit"
public comment_status -> string (4) "open"
public ping_status -> string (6) "closed"
public post_password -> string (0) ""
public post_name -> string (24) "dsc20050604_133440_34211"
public to_ping -> string (0) ""
public pinged -> string (0) ""
public post_modified -> string (19) "2013-09-18 14:37:07"
public post_modified_gmt -> string (19) "2013-09-18 21:37:07"
public post_content_filtered -> string (0) ""
public post_parent -> integer 0
public guid -> string (76) "http://dev.rarst.net/wp-content/uploads/2013/09/dsc20050604_133440_34211.jpg"
public menu_order -> integer 0
public post_type -> string (10) "attachment"
public post_mime_type -> string (10) "image/jpeg"
public comment_count -> string (1) "0"
public filter -> string (3) "raw"
}
array(2) [
\'_wp_attached_file\' => array(1) [
string (36) "2013/09/dsc20050604_133440_34211.jpg"
]
\'_wp_attachment_metadata\' => array(1) [
string (687) "a:5:{s:5:"width";i:640;s:6:"height";i:480;s:4:"file";s:36:"2013/09/dsc20050604_133440_34211.jpg";s:5:"sizes";a:2:{s:9:"thumbnail";a:4:{s:4:"file";s:36:"dsc20050604_133440_34211-150x150.jpg";s:5:"width";i:150;s:6:"height";i:150;s:9:"mime-type";s:10:"image/jpeg";}s:6:"medium";a:4:{s:4:"file";s:36:"dsc20050604_133440_34211-300x225.jpg";s:5:"width";i:300;s:6:"height";i:225;s:9:"mime-type";s:10:"image/jpeg";}}s:10:"image_meta";a:10:{s:8:"aperture";d:2;s:6:"credit";s:0:"";s:6:"camera";s:9:"CYBERSHOT";s:7:"caption";s:0:"";s:17:"created_timestamp";i:1117892080;s:9:"copyright";s:0:"";s:12:"focal_length";s:3:"9.7";s:3:"iso";s:3:"100";s:13:"shutter_speed";s:6:"0.0125";s:5:"title";s:0:"";}}"
]
]
要点分别针对您的问题：
在guid 字段执行not 重要的是，它保存了一个计算URL的副本（但在WP上下文中，它并不是可靠的URL），大多数情况下应该被忽略not 工作，它将破坏中的序列化字符串_wp_attachment_metadata 元字段。您需要支持序列化的搜索/替换工具，有很多（WP CLI、search replace DB等）
