explain UPDATE xmlsitemap SET subtype='navigation', loc='node/%/log', language='und', access='0', status='0', status_override='0', lastmod='0', priority='0.5', priority_override='0', changefreq='0', changecount='0'\nWHERE (type = 'menu_link') AND (id = '636');
+------+-------------+------------+-------+----------------------+---------+---------+------+------+-------------+
| id   | select_type | table      | type  | possible_keys        | key     | key_len | ref  | rows | Extra       |
+------+-------------+------------+-------+----------------------+---------+---------+------+------+-------------+
|    1 | SIMPLE      | xmlsitemap | range | PRIMARY,type_subtype | PRIMARY | 102     | NULL |    1 | Using where |
+------+-------------+------------+-------+----------------------+---------+---------+------+------+-------------+

explain select * from xmlsitemap where  (type = 'menu_link') AND (id = '636');
+------+-------------+------------+-------+----------------------+---------+---------+-------------+------+-------+
| id   | select_type | table      | type  | possible_keys        | key     | key_len | ref         | rows | Extra |
+------+-------------+------------+-------+----------------------+---------+---------+-------------+------+-------+
|    1 | SIMPLE      | xmlsitemap | const | PRIMARY,type_subtype | PRIMARY | 102     | const,const |    1 |       |
+------+-------------+------------+-------+----------------------+---------+---------+-------------+------+-------+

CREATE TABLE `xmlsitemap` (
  `id` int(10) unsigned NOT NULL DEFAULT '0' COMMENT 'Primary key with type; a unique id for the item.',
  `type` varchar(32) NOT NULL DEFAULT '' COMMENT 'Primary key with id; the type of item (e.g. node, user, etc.).',
  `subtype` varchar(128) NOT NULL DEFAULT '' COMMENT 'A sub-type identifier for the link (node type, menu name, term VID, etc.).',
  `loc` varchar(255) NOT NULL DEFAULT '' COMMENT 'The URL to the item relative to the Drupal path.',
  `language` varchar(12) NOT NULL DEFAULT '' COMMENT 'The languages.language of this link or an empty string if it is language-neutral.',
  `access` tinyint(4) NOT NULL DEFAULT '1' COMMENT 'A boolean that represents if the item is viewable by the anonymous user. This field is useful to store the result of node_access() so we can retain changefreq and priority_override information.',
  `status` tinyint(4) NOT NULL DEFAULT '1' COMMENT 'An integer that represents if the item is included in the sitemap.',
  `status_override` tinyint(4) NOT NULL DEFAULT '0' COMMENT 'A boolean that if TRUE means that the status field has been overridden from its default value.',
  `lastmod` int(10) unsigned NOT NULL DEFAULT '0' COMMENT 'The UNIX timestamp of last modification of the item.',
  `priority` float DEFAULT NULL COMMENT 'The priority of this URL relative to other URLs on your site. Valid values range from 0.0 to 1.0.',
  `priority_override` tinyint(4) NOT NULL DEFAULT '0' COMMENT 'A boolean that if TRUE means that the priority field has been overridden from its default value.',
  `changefreq` int(10) unsigned NOT NULL DEFAULT '0' COMMENT 'The average time in seconds between changes of this item.',
  `changecount` int(10) unsigned NOT NULL DEFAULT '0' COMMENT 'The number of times this item has been changed. Used to help calculate the next changefreq value.',
  PRIMARY KEY (`id`,`type`),
  KEY `loc` (`loc`),
  KEY `access_status_loc` (`access`,`status`,`loc`),
  KEY `type_subtype` (`type`,`subtype`),
  KEY `language` (`language`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='The base table for xmlsitemap links.'