優化SQL查詢

Question

我有查詢到最多40秒來執行，我想知道如何使它更快...

SELECT rp.`id` as rip,r.`id`, 
    rl.`id` as rlid, r.`number`, r.`type`, 
    a.`title` as atitle, a.`id` as aid, more, 
    more_valid 
FROM 
    `R_l_p` rp INNER JOIN 
    `Rl` rl ON rp.`rl_id` = rl.`id` INNER JOIN 
    `R` r ON r.`id` = rl.`r_id` INNER JOIN 
    `A` a ON a.`id` = r.`a_id` 
    LEFT JOIN 
    (SELECT `type`, `v`, `r_id`, COUNT(*) AS more 
    FROM `R_l` 
    WHERE `type` = 'stream' AND `v` = 1 
    GROUP BY `r_id`) stm ON stm.`r_id` = r.`id` 
    LEFT JOIN 
    (SELECT `type`, `v`, `r_id`, COUNT(*) AS more_valid 
    FROM `R_l` 
    WHERE `type` = 'stream' AND `v` = 0 
    GROUP BY `r_id`) morelink ON morelink.`r_id` = r.`id` 
WHERE rp.`link` = 'dead' AND rl.`type` = 'stream' 
ORDER BY rip ASC 
LIMIT 0, 1000 

 
+-----+--------------+---------------+---------+--------------------------+-------------+----------+---------------------------+--------+----------------------------------------------+ 
| id | select_type | table  | type |  possible_keys  | key  | key_len |   ref    | rows |     Extra      | 
+-----+--------------+---------------+---------+--------------------------+-------------+----------+---------------------------+--------+----------------------------------------------+ 
| 1 | PRIMARY  | r    | ALL  | PRIMARY,a_id    | NULL  | NULL  | NULL      | 21804 | Using temporary; Using filesort    | 
| 1 | PRIMARY  | a    | eq_ref | PRIMARY     | PRIMARY  | 4  | db453988339.r.a_id  |  1 |            | 
| 1 | PRIMARY  | rl   | ref  | PRIMARY,r_id,type  | r_id  | 4  | db453988339.r.id   |  1 | Using where         | 
| 1 | PRIMARY  | derived2  | ALL  | NULL      | NULL  | NULL  | NULL      | 21077 |            | 
| 1 | PRIMARY  | derived3  | ALL  | NULL      | NULL  | NULL  | NULL      |  1 |            | 
| 1 | PRIMARY  | rp   | eq_ref | rl_id     | rl_id  | 4  | db453988339.rl.id   |  1 | Using where         | 
| 3 | DERIVED  | R_link  | ALL  | type      | NULL  | NULL  | NULL      | 27580 | Using where; Using temporary; Using filesort | 
| 2 | DERIVED  | R_link  | ALL  | type      | NULL  | NULL  | NULL      | 27580 | Using where; Using temporary; Using filesort | 
+-----+--------------+---------------+---------+--------------------------+-------------+----------+---------------------------+--------+----------------------------------------------+ 

謝謝:)

Answer 1

一件事，我會用一個內嵌視圖替換兩個內聯視圖，通過將條件從WHERE子句移動到SELECT列表中的表達式中，從同一個內聯視圖中返回more和more_valid），並刪除more_link視圖。

我修改stm聯視圖是這樣的：

 (SELECT q.r_id 
       , SUM(q.v=1) AS `more` 
       , SUM(q.v=0) AS `more_valid` 
      FROM `R_l` q 
      WHERE q.type = 'stream' 
      GROUP BY q.r_id 
     ) stm 

我還提供覆蓋索引，以優化聯視圖查詢，例如：

CREATE INDEX R_1_IX1 ON R_1 (type, r_id, v) 

通過引用列type上的等式謂詞，MySQL可能能夠使用索引優化GROUP BY操作（避免使用「使用filesort」操作）。我們希望在解釋的額外列中看到「使用索引」。

不幸的是，派生表不會被編入索引。但至少在這種變化的情況下，你只能實現一個內聯視圖，避免額外的聯接操作。

---

也就是說，我會更換這些兩行：

LEFT JOIN (SELECT `type`, `v`, `r_id`, COUNT(*) AS more FROM `R_l` WHERE `type` = 'stream' AND `v` = 1 GROUP BY `r_id`) stm ON stm.`r_id` = r.`id` 
LEFT JOIN (SELECT `type`, `v`, `r_id`, COUNT(*) AS more_valid FROM `R_l` WHERE `type` = 'stream' AND `v` = 0 GROUP BY `r_id`) morelink ON morelink.`r_id` = r.`id` 

有了這個：

LEFT 
    JOIN (SELECT q.r_id 
       , SUM(q.v=1) AS `more` 
       , SUM(q.v=0) AS `more_valid` 
      FROM `R_l` q 
      WHERE q.type = 'stream' 
      GROUP BY q.r_id 
     ) stm 
    ON stm.r_id = r.id