MySQL indexes

In this MySQL table we have indexes for `post_name`, `post_parent`, `post_author` and (`post_type`,`post_status`,`post_date`,`ID`):

CREATE TABLE `wp_posts` (

  `ID` bigint(20) unsigned NOT NULL auto_increment,

  `post_author` bigint(20) unsigned NOT NULL default '0',

  `post_date` datetime NOT NULL default '0000-00-00 00:00:00',

  `post_date_gmt` datetime NOT NULL default '0000-00-00 00:00:00',

  `post_content` longtext NOT NULL,

  `post_title` text NOT NULL,

  `post_excerpt` text NOT NULL,

  `post_status` varchar(20) NOT NULL default 'publish',

  `comment_status` varchar(20) NOT NULL default 'open',

  `ping_status` varchar(20) NOT NULL default 'open',

  `post_password` varchar(20) NOT NULL default '',

  `post_name` varchar(200) NOT NULL default '',

  `to_ping` text NOT NULL,

  `pinged` text NOT NULL,

  `post_modified` datetime NOT NULL default '0000-00-00 00:00:00',

  `post_modified_gmt` datetime NOT NULL default '0000-00-00 00:00:00',

  `post_content_filtered` text NOT NULL,

  `post_parent` bigint(20) unsigned NOT NULL default '0',

  `guid` varchar(255) NOT NULL default '',

  `menu_order` int(11) NOT NULL default '0',

  `post_type` varchar(20) NOT NULL default 'post',

  `post_mime_type` varchar(100) NOT NULL default '',

  `comment_count` bigint(20) NOT NULL default '0',

  PRIMARY KEY  (`ID`),

  KEY `post_name` (`post_name`),

  KEY `type_status_date` (`post_type`,`post_status`,`post_date`,`ID`),

  KEY `post_parent` (`post_parent`),

  KEY `post_author` (`post_author`)

) ENGINE=MyISAM DEFAULT CHARSET=utf8 ;

So this sql select will work in about 10 times faster:

SELECT * 

FROM {$wpdb->posts} 

WHERE  `post_parent`=0

than this one:

SELECT * 

FROM {$wpdb->posts}

WHERE  `menu_order`=0