mysql - CakePHP HAVING SUM 查询超慢 - 哪里有改进的空间？

Question

此查询会杀死整个页面(90% 的请求时间):

/**
 * Checks if a conversation exists containing these users (at least two!)
 * //TODO: fixme! SUPER-SLOW! 5s on a 6s page load total
 *
 * @param array $users Users to check on
 * @param int $limit Limit - needs at least 2 users
 * @return array Results
 */
public function partOfConversations($users, $limit = 5) {
    $options = array(
        'conditions' => array('ConversationUser.status <' => ConversationUser::STATUS_REMOVED),
        'group' => array('ConversationUser.conversation_id HAVING SUM(CASE WHEN ConversationUser.`user_id` in (\'' . implode('\', \'', $users) . '\') THEN 1 ELSE 0 END) = ' . count($users) . ''),
        'contain' => array('Conversation' => array('LastMessage')),
        'limit' => $limit,
        'order' => array('Conversation.last_message_id' => 'DESC')
    );
    return $this->ConversationUser->find('all', $options);
}

结果查询是

SELECT `ConversationUser`.`id`, `ConversationUser`.`conversation_id`,
    `ConversationUser`.`user_id`, `ConversationUser`.`status`, `ConversationUser`.`created`, 
    `Conversation`.`id`, `Conversation`.`user_id`, `Conversation`.`title`, 
    `Conversation`.`created`, `Conversation`.`last_message_id`, `Conversation`.`count` 
FROM `comm_conversation_users` AS `ConversationUser` 
LEFT JOIN `comm_conversations` AS `Conversation` 
    ON (`ConversationUser`.`conversation_id` = `Conversation`.`id`) 
WHERE `ConversationUser`.`status` < 7 GROUP BY `ConversationUser`.`conversation_id` 
HAVING SUM(CASE WHEN `ConversationUser`.`user_id` in 
    ('2ed23d7c-dcc8-4d3b-8e7b-0fe018b0f9bf', '297e0fcc-8880-4bc7-9b57-0ba418b0f9bf') 
    THEN 1 ELSE 0 END) = 2 
ORDER BY `Conversation`.`last_message_id` DESC 
LIMIT 5

它试图做的是查明 1..x 对话中是否有两个或更多用户参与(作为 $users 传递)。有什么办法可以加快速度吗？

对话 1:N ConversationUser N:1 用户

记录不是太多:70k Conversation，130k ConversationUser

事实上，这也使用 UUIds 而不是普通的 AIID 整数，这可能会让情况变得更糟。但应该还是不到5秒。

Answer 1

除了确保您的 sql 表通过该查询的索引进行优化之外，我认为您应该添加另一个条件 - 仅那些具有可接受的 user_id 的记录。

这是适当的 WHERE 子句

WHERE `ConversationUser`.`status` < 7 
  AND `ConversationUser`.`user_id` in 
    ('2ed23d7c-dcc8-4d3b-8e7b-0fe018b0f9bf', '297e0fcc-8880-4bc7-9b57-0ba418b0f9bf')

将 PHP 代码更改为:

public function partOfConversations($users, $limit = 5) {
    $options = array(
        'conditions' => array('ConversationUser.status <' => ConversationUser::STATUS_REMOVED
                              ,'ConversationUser.user_id' => $users),
        'group' => array('ConversationUser.conversation_id HAVING SUM(CASE WHEN ConversationUser.`user_id` in (\'' . implode('\', \'', $users) . '\') THEN 1 ELSE 0 END) = ' . count($users) . ''),
        'contain' => array('Conversation' => array('LastMessage')),
        'limit' => $limit,
        'order' => array('Conversation.last_message_id' => 'DESC')
    );
    return $this->ConversationUser->find('all', $options);
}