将s3图像设置为wordpress帖子中的特色图像，同时以编程方式从外部源发布帖子

I am pretty much new to wordpress. My requirement is that i need to make a post from an external source using ajax to wordpress site. The post data merely contain "posttitle,description,etc..." and an "imageurl" which is pre-uploaded to amazon s3. I am succcessfully able to post the data using the following reference http://codex.wordpress.org/Function_Reference/wp_insert_post#Example

but i need to save the s3 url (external image) to worpress post tables and show it as a featured image without again uploading to wordpress server.

To figure out how the images are being saved, I logged into wp admin and created a post with featured image, searched wp tables for image path and it is saving image relative path in 'postmeta' table as below.

The images are stored with relative reference path.Then i thought even if i forcefully insert s3 url (which is absolute),wordpress might not be able to recoginize it as it might always be searching for local files.How do i achieve inserting s3 urls into wordpress tables and make them show up in my posts. I searched everywhere but couldn't find solution for this particular case. Any help is appreciated. Thanks in advance.

You can use a absolute path in the guid field in the posts table for the featured image with post_type set to attachment.

The image is set to Featured for a given post by adding it to the postmeta table with the post ID and the featured image post ID and meta_key = _thumbnail_id.

INSERT INTO $wp->post 
    (post_type, guid, status, post_mime_type) 
VALUES 
    ('attachment', '<imageUrl>', 'publish', 'image/jpeg');

INSERT INTO $wp->postmeta 
    (meta_value, meta_key, post_id) 
VALUES 
    ('<imagePostID>', '_thumbnail_id', '<postID>');