PHP 板慢 mysql

Question

我有多个 table 个 php 板。

我需要一个有效的查询，select 所有类别、所有主题、最后 post 个主题，以及 posted 用户。对于我的查询，运行需要 5-8 秒。我使用 last_post_id 字段对主题 table 进行了优化，但我需要一个更好的解决方案。

结构

forum_categories ~ 15 lines
id|name|...

forum_topics ~ 150 lines
id|name|category_id|...

forum_posts ~ 1.000.000 lines
id|body|topic_id|user_id|...

users ~ 30.000 lines
id|username|...


category 1
 - topic 1
    - last post1 | user1
 - topic 2
    - last post2 | user2
 ...
category 2
 - topic 3
   - last post3 | user3
 ...
...

上次查询（这是我朋友的帮助，但也太慢了。）

SELECT c.NAME     AS category, 
       t.NAME     AS topic, 
       p.body     AS post, 
       p.username AS username 
FROM   forum_categories AS c 
       JOIN forum_topics AS t 
         ON t.category_id = c.id 
       JOIN (SELECT * 
             FROM   (SELECT p.body, 
                            p.topic_id, 
                            u.username 
                     FROM   forum_posts AS p 
                            JOIN users AS u 
                              ON u.id = p.user_id 
                     ORDER  BY p.id DESC) AS t 
             GROUP  BY topic_id) AS p 
         ON t.id = p.topic_id

解释查询

查询统计

Headers分别是：排序、状态、时间|状态，所有时间， pct。时间，电话，时间

Answer 1

我认为 "last post of topics" 是您查询的关键点。这就是为什么您在大多数内部查询中使用 ORDER BY 但这会产生两个子查询。

更新版本

CREATE TEMPORARY TABLE last_post_per_topic_t ENGINE = MEMORY
SELECT topic_id, MAX(id) AS id -----+
FROM forum_posts                    --> find last post id per topic
GROUP BY topic_id; -----------------+

ALTER TABLE last_post_per_topic_t ADD INDEX (id, topic_id);

SELECT *
FROM forum_categories AS c INNER JOIN forum_topics t ON c.id = t.category_id
INNER JOIN forum_posts p ON p.topic_id = t.id
INNER JOIN last_post_per_topic_t ON last_post_per_topic_t.topic_id = t.id
  AND last_post_per_topic_t.id = p.id;
INNER JOIN users u ON p.user_id = u.id;

第一个版本

SELECT *
FROM forum_categories AS c INNER JOIN forum_topics t ON c.id = t.category_id
INNER JOIN forum_posts p ON p.topic_id = t.id
INNER JOIN (
    SELECT topic_id, MAX(id) AS id -----+
    FROM forum_posts                    --- find last post_id per topic
    GROUP BY topic_id    ---------------+
) last_post_per_topic_t ON last_post_per_topic_t.topic_id = t.id
  AND last_post_per_topic_t.id = p.id;

PHP 板慢 mysql

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更新版本

第一个版本