How can I change the admin search posts fields?

Question

I have a custom post type that includes many custom fields. I would like to add them as a search target to admin search.

Currently the admin search searches only the content and the title, I would like it to search these custom fields as well.

Is there a way to do that ?

Answer 1

It is possible, but you'll have to play a little bit with the actual query. As always, the furious posts_clauses filter comes to action:

function wpse_alter_posts_search( $pieces )
{
    global $wpdb;

    // Make the input save
    $search_string = like_escape( $_GET['s'] );

    // Your new WHERE clause
    $where  = $wpdb->prepare(
        "$wpdb->postmeta.%s LIKE %s",
        'YOUR_COLUMN', // Should match your col name 1)
        "%{$search_string}%"
    );

    // Not sure if this exactly the same on your install 2)
    $pieces['where'] = str_replace( 'AND (((', "AND ((({$where} ", $pieces['where'] );

    return $pieces;
}
add_filter( 'posts_clauses', 'wpse_alter_posts_search' );

---

NOTES

1. Could be that you need to unserialize some parts to be search able.
2. You better simply dump the $pieces to take a look into them, before altering the query (right after the $search_string was received).

Answer 2

kaiser's answer got me on the right track but I had to join the postmeta table and add a group by as well.

Now like_escape is $wpdb->esc_like. Replace [your_post_type] with your post type and [your_postmeta_key] with your meta key:

//join postmeta for search
add_filter( 'posts_join' , function($join){
    global $wpdb;
    if(is_search() && is_admin() && $_GET['post_type'] == '[your_post_type]')
    {
     $join .= " LEFT JOIN $wpdb->postmeta ON $wpdb->posts.ID = $wpdb->postmeta.post_id ";
    }
     return $join;
});

//search [your_postmeta_key] for search string
add_filter( 'posts_where', function( $where )
{
    global $wpdb;
    if(is_search() && is_admin() && $_GET['post_type'] == '[your_post_type]')
    {
        $searchstring = '%' . $wpdb->esc_like( $_GET['s'] ) . '%';
        //search [your_postmeta_key] as well
        $where .= $wpdb->prepare(" OR ($wpdb->postmeta.meta_key = '[your_postmeta_key]' AND $wpdb->postmeta.meta_value LIKE %s) ", $searchstring);   
    }
    return $where;
});

//group by post ID
add_filter( 'posts_groupby', function ($groupby, $query) {

    global $wpdb;
    if(is_search() && is_admin() && $_GET['post_type'] == '[your_post_type]')
    {
        $groupby = "{$wpdb->posts}.ID";
    }
    return $groupby;

}, 10, 2 );