How to filter post listing (in WP dashboard posts listing) using a custom field (search functionality)?

I coded a plugin just for that and never got around to publish it :

Usage:

In the dropdown you have a list of all custom fields, so just select the field you want to filter by and click filter. if you want to filter to a specific value of a custom field then select the field’s name , enter the value you want and click filter.

<?php
/*
Plugin Name: Admin Filter BY Custom Fields
Plugin URI: http://en.bainternet.info
Description: Filter posts or pages in admin by custom fields (post meta)
Version: 1.0
Author: Bainternet
Author URI: http://en.bainternet.info
*/



add_filter( 'parse_query', 'ba_admin_posts_filter' );
add_action( 'restrict_manage_posts', 'ba_admin_posts_filter_restrict_manage_posts' );

function ba_admin_posts_filter( $query )
{
    global $pagenow;
    if ( is_admin() && $pagenow=='edit.php' && isset($_GET['ADMIN_FILTER_FIELD_NAME']) && $_GET['ADMIN_FILTER_FIELD_NAME'] != '') {
        $query->query_vars['meta_key'] = $_GET['ADMIN_FILTER_FIELD_NAME'];
    if (isset($_GET['ADMIN_FILTER_FIELD_VALUE']) && $_GET['ADMIN_FILTER_FIELD_VALUE'] != '')
        $query->query_vars['meta_value'] = $_GET['ADMIN_FILTER_FIELD_VALUE'];
    }
}

function ba_admin_posts_filter_restrict_manage_posts()
{
    global $wpdb;
    $sql="SELECT DISTINCT meta_key FROM ".$wpdb->postmeta.' ORDER BY 1';
    $fields = $wpdb->get_results($sql, ARRAY_N);
?>
<select name="ADMIN_FILTER_FIELD_NAME">
<option value=""><?php _e('Filter By Custom Fields', 'baapf'); ?></option>
<?php
    $current = isset($_GET['ADMIN_FILTER_FIELD_NAME'])? $_GET['ADMIN_FILTER_FIELD_NAME']:'';
    $current_v = isset($_GET['ADMIN_FILTER_FIELD_VALUE'])? $_GET['ADMIN_FILTER_FIELD_VALUE']:'';
    foreach ($fields as $field) {
        if (substr($field[0],0,1) != "_"){
        printf
            (
                '<option value="%s"%s>%s</option>',
                $field[0],
                $field[0] == $current? ' selected="selected"':'',
                $field[0]
            );
        }
    }
?>
</select> <?php _e('Value:', 'baapf'); ?><input type="TEXT" name="ADMIN_FILTER_FIELD_VALUE" value="<?php echo $current_v; ?>" />
<?php
}