Долгие запросы MySql

CREATE TABLE `cms_con_anec` (
 `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
 `title` VARCHAR(255) DEFAULT NULL,
 `content` text DEFAULT NULL,
 `photo` text DEFAULT NULL,
 `slug` VARCHAR(100) DEFAULT NULL,
 `seo_keys` VARCHAR(256) DEFAULT NULL,
 `seo_desc` VARCHAR(256) DEFAULT NULL,
 `seo_title` VARCHAR(256) DEFAULT NULL,
 `tags` VARCHAR(1000) DEFAULT NULL,
 `date_pub` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP(),
 `date_last_modified` TIMESTAMP NULL DEFAULT NULL,
 `date_pub_end` TIMESTAMP NULL DEFAULT NULL,
 `is_pub` tinyint(1) UNSIGNED NOT NULL DEFAULT 1,
 `hits_count` INT(11) UNSIGNED NOT NULL DEFAULT 0,
 `user_id` INT(11) UNSIGNED DEFAULT NULL,
 `parent_id` INT(11) UNSIGNED DEFAULT NULL,
 `parent_type` VARCHAR(32) DEFAULT NULL,
 `parent_title` VARCHAR(100) DEFAULT NULL,
 `parent_url` VARCHAR(255) DEFAULT NULL,
 `is_parent_hidden` tinyint(1) UNSIGNED DEFAULT NULL,
 `category_id` INT(11) UNSIGNED NOT NULL DEFAULT 1,
 `folder_id` INT(11) UNSIGNED DEFAULT NULL,
 `is_comments_on` tinyint(1) UNSIGNED NOT NULL DEFAULT 1,
 `comments` INT(11) UNSIGNED NOT NULL DEFAULT 0,
 `rating` INT(11) NOT NULL DEFAULT 0,
 `is_deleted` tinyint(1) UNSIGNED DEFAULT NULL,
 `is_approved` tinyint(1) UNSIGNED NOT NULL DEFAULT 1,
 `approved_by` INT(11) UNSIGNED DEFAULT NULL,
 `date_approved` TIMESTAMP NULL DEFAULT NULL,
 `is_private` tinyint(1) UNSIGNED NOT NULL DEFAULT 0,
 PRIMARY KEY (`id`),
 KEY `dataset_best` (`is_pub`,`is_parent_hidden`,`is_deleted`,`is_approved`,`rating`),
 KEY `dataset_best_yearly` (`date_pub`,`is_pub`,`is_parent_hidden`,`is_deleted`,`is_approved`,`rating`),
 KEY `slug` (`slug`),
 KEY `date_pub` (`is_pub`,`is_parent_hidden`,`is_deleted`,`is_approved`,`date_pub`,`parent_id`,`rating`) USING BTREE,
 KEY `user_id` (`user_id`,`date_pub`,`is_deleted`) USING BTREE,
 KEY `dataset_random` (`is_pub`,`is_parent_hidden`,`is_deleted`,`is_approved`,`title`),
 KEY `parent_id` (`parent_id`),
 FULLTEXT KEY `content` (`title`,`content`)
) ENGINE=MyISAM AUTO_INCREMENT=128905 DEFAULT CHARSET=utf8 AVG_ROW_LENGTH=446

SELECT i.*, u.nickname AS user_nickname, f.title AS folder_title
FROM cms_con_anec i
FORCE INDEX FOR ORDER BY (date_pub)
INNER JOIN cms_users AS u FORCE INDEX (PRIMARY) ON u.id = i.user_id
LEFT JOIN cms_content_folders AS f ON f.id = i.folder_id
WHERE (i.is_parent_hidden IS NULL) AND (i.rating > '-20') AND (i.is_deleted IS NULL) AND (i.is_pub = '1')
ORDER BY i.date_pub DESC
LIMIT 0, 30
Время выполнения 0.00471 секунд

/system\controllers\comments\model.php => 298 => modelComments->getComments()
SELECT i.*, r.score AS is_rated, u.nickname AS user_nickname, u.avatar AS user_avatar
FROM cms_comments i
LEFT JOIN cms_users AS u ON u.id = i.user_id
LEFT JOIN cms_comments_rating AS r ON r.comment_id = i.id AND r.user_id='86'
WHERE (i.user_id = '86') AND (i.is_deleted IS NULL)
ORDER BY i.is_approved DESC, i.date_pub DESC
LIMIT 0, 20
Время выполнения 15.11935 секунд

 Отображение строк 0 - 19 (20 всего, Запрос занял 0.0310 сек.) [date_pub: 2018-02-10 01:19:23... - 2018-02-08 20:10:31...]
SELECT i.*, r.score AS is_rated, u.nickname AS user_nickname, u.avatar AS user_avatar FROM cms_comments i LEFT JOIN cms_users AS u ON u.id = i.user_id LEFT JOIN cms_comments_rating AS r ON r.comment_id = i.id AND r.user_id='86' WHERE (i.user_id = '86') AND (i.is_deleted IS NULL) ORDER BY i.date_pub DESC LIMIT 0, 20

 
# Query_time: 51.697987  Lock_time: 0.000473  Rows_sent: 20  Rows_examined: 1843896
SET TIMESTAMP=1520069949;
SELECT   i.*, r.score AS is_rated, u.nickname AS user_nickname, u.avatar AS user_avatar
                FROM cms_comments i
                LEFT JOIN cms_users AS u ON u.id = i.user_id
LEFT JOIN cms_comments_rating AS r ON r.comment_id = i.id AND r.user_id='0'
WHERE (i.is_private = '0')  AND  (i.is_deleted IS NULL)  AND  (i.is_approved = '1')
ORDER BY i.date_pub DESC
LIMIT 922000, 20;

// Получаем количество и список записей
        $total = !empty($this->count) ? $this->count : $this->model->getCommentsCount();
		$this->model->limit($perpage)->join .= ("JOIN (SELECT id FROM cms_comments ORDER BY id DESC LIMIT ".($page-1)*$perpage.", $perpage ) c ON c.id = i.id ");
        $items = $this->model->getComments();

/system\controllers\comments\model.php => 296 => modelComments->getComments()
SELECT i.*, r.score AS is_rated, u.nickname AS user_nickname, u.avatar AS user_avatar
FROM cms_comments i
JOIN (SELECT id FROM cms_comments ORDER BY id DESC LIMIT 958740, 20 ) c ON c.id = i.id LEFT JOIN cms_users AS u ON u.id = i.user_id
LEFT JOIN cms_comments_rating AS r ON r.comment_id = i.id AND r.user_id='86'
WHERE (i.is_deleted IS NULL) AND (i.is_approved = '1')
ORDER BY i.date_pub DESC
LIMIT 20
Время выполнения 0.22628 секунд

// Получаем количество и список записей
        $total = !empty($this->count) ? $this->count : $this->model->getCommentsCount();
		if (strpos($_SERVER['REQUEST_URI'], 'comments/all')) {$this->model->limit($perpage)->join .= ("JOIN (SELECT id FROM cms_comments ORDER BY id DESC LIMIT ".($page-1)*$perpage.", $perpage ) c ON c.id = i.id ");}
        $items = $this->model->getComments();