如果要扩展查询，应通过pre_get_posts-滤器那就做一个"Custom Field" or meta query.

add_action( \'pre_get_posts\', \'wpse105969_extended_search\' );
function wpse105969_extended_search( $query )
{
    // Make sure we got a search query
    // and we\'re only modifying the main query.
    if (
        ! $query->is_main_query()
        AND \'\' === $query->get( \'s\' )
        AND \'your_custom_post_type\' === $query->get( \'post_type\' )
    )
        return $query;

    // Alter whatever you need: Make, Model, etc.
    $query->set( \'meta_query\', array(
        \'relation\' => \'OR\',
        array(
            \'key\'     => \'color\',
            \'value\'   => \'blue\',
            \'compare\' => \'NOT LIKE\'
        ),
        array(
            \'key\'     => \'price\',
            \'value\'   => array( 20, 100 ),
            \'type\'    => \'numeric\',
            \'compare\' => \'BETWEEN\'
        )
    ) );

    return $query;
}

这是代码。你可以改变$post_type 和$custom_fields 根据您的需要。

function extend_admin_search( $query ) {

    // Extend search for document post type
    $post_type = \'document\';
    // Custom fields to search for
    $custom_fields = array(
        "_file_name",
    );

    if( ! is_admin() )
        return;

    if ( $query->query[\'post_type\'] != $post_type )
        return;

    $search_term = $query->query_vars[\'s\'];

    // Set to empty, otherwise it won\'t find anything
    $query->query_vars[\'s\'] = \'\';

    if ( $search_term != \'\' ) {
        $meta_query = array( \'relation\' => \'OR\' );

        foreach( $custom_fields as $custom_field ) {
            array_push( $meta_query, array(
                \'key\' => $custom_field,
                \'value\' => $search_term,
                \'compare\' => \'LIKE\'
            ));
        }

        $query->set( \'meta_query\', $meta_query );
    };
}

add_action( \'pre_get_posts\', \'extend_admin_search\' );