MySQL的慢大型查詢

我有我想要優化這個大的查詢，我已經優化的，但它仍然是慢了一些次（> 1秒）：MySQL的慢大型查詢

select count(DISTINCT if(ps15.specification in ('All Season'),p.products_id,NULL)) as count1 ,count(DISTINCT if(ps15.specification in ('Winter'),p.products_id,NULL)) as count2 ,count(DISTINCT if(ps15.specification in ('Zomer'),p.products_id,NULL)) as count3 ,count(DISTINCT if(ps15.specification in ('Winter 2012'),p.products_id,NULL)) as count4 ,count(DISTINCT if(ps15.specification in ('Zomer 2013'),p.products_id,NULL)) as count5 ,count(DISTINCT if(ps15.specification in ('Winter 2013'),p.products_id,NULL)) as count6 ,count(DISTINCT if(ps15.specification in ('Zomer 2014'),p.products_id,NULL)) as count7 
from (products p) 
inner join (products_to_categories p2c) 
    on (p.products_id = p2c.products_id) 
inner join (products_attributes pa) 
    on (p.products_id = pa.products_id) 
inner join (products_options_values pv) 
    on (pa.options_values_id = pv.products_options_values_id) 
inner join (products_stock ps) 
    on (p.products_id=ps.products_id 
    and pv.products_options_values_id = ps.products_options_values_id2 
    and ps.products_stock_quantity>0) 
INNER JOIN products_specifications ps15 
    ON p.products_id = ps15.products_id 
    AND ps15.specifications_id = '15' 
    AND ps15.language_id = '1' 
INNER JOIN products_specifications ps10 
    ON p.products_id = ps10.products_id 
    AND ps10.specifications_id = '10' 
    AND ps10.language_id = '1' 
where p.products_status = '1' 
    and p2c.categories_id in (72,1,23,100,74,24,33,34,35,77,110,25,45,44,40,41,42,85,76,78,83,102,107,111,119,50,52,81,105,108,112,86,88,87,98,89,90,91,96,79,2,54,60,82,109,115,118,53,58,104,55,101,75,56,64,66,67,68,69,70,71,84,103,114,120,80,92,99,93,94,95,97,106,121) 
    AND ps10.specification in ('Meisje') 
    and products_options_values_name in (62,"3M/60cm","56-62","0-4 mnd","3m","0-3m","3-6m","3M","62/68","0-6m","50-62" , 68,"6M/67cm","9M/70cm","4-8 mnd","6m","3-6m","6M","62/68","0-6m" , 74,"4-8 mnd","8-12 mnd","6m","9m","6-9m","6M","9M","74/80","6-12m");

輸出爲：

+--------+--------+--------+--------+--------+--------+--------+ 
| count1 | count2 | count3 | count4 | count5 | count6 | count7 | 
+--------+--------+--------+--------+--------+--------+--------+ 
|  1 | 289 | 193 |  49 | 192 | 240 |  0 | 
+--------+--------+--------+--------+--------+--------+--------+

講解MySQL的輸出：

+----+-------------+-------+-------+-------------------------------------------+-------------------------------------+---------+---------------------------------------+------+--------------------------+ 
| id | select_type | table | type | possible_keys        | key         | key_len | ref         | rows | Extra     | 
+----+-------------+-------+-------+-------------------------------------------+-------------------------------------+---------+---------------------------------------+------+--------------------------+ 
| 1 | SIMPLE  | p  | index | PRIMARY,products_id      | products_id       | 5  | NULL         | 4539 | Using where; Using index | 
| 1 | SIMPLE  | p2c | ref | PRIMARY         | PRIMARY        | 4  | kikleding.p.products_id    | 1 | Using where; Using index | 
| 1 | SIMPLE  | ps15 | ref | products_id        | products_id       | 12  | kikleding.p2c.products_id,const,const | 1 | Using where    | 
| 1 | SIMPLE  | ps10 | ref | products_id        | products_id       | 12  | kikleding.p.products_id,const,const | 1 | Using where    | 
| 1 | SIMPLE  | pa | ref | idx_products_attributes_products_id  | idx_products_attributes_products_id | 4  | kikleding.p.products_id    | 6 |       | 
| 1 | SIMPLE  | pv | ref | PRIMARY         | PRIMARY        | 4  | kikleding.pa.options_values_id  | 2 | Using where    | 
| 1 | SIMPLE  | ps | ref | idx_products_stock_attributes,products_id | idx_products_stock_attributes  | 4  | kikleding.ps15.products_id   | 6 | Using where    | 
+----+-------------+-------+-------+-------------------------------------------+-------------------------------------+---------+---------------------------------------+------+--------------------------+

我試圖指數大部分表，裁判仍然給前的第一排NULL平原。

它現在輸出7列，有時我需要輸出50列。

有什麼建議嗎？

來源

2013-10-18 Md Dang

什麼是'products_options_values_names'？它屬於「產品」表嗎？如果是，它可能是一個選項來標準化您的數據模型，因此優化器可以使用外鍵。 – ErnestV

它包含在product_options_values表中 –

什麼是您的服務器的硬件規格，並且您確定您的緩衝區足夠大？（查詢很簡單，並且計算7 x 4k行不應該花很長的時間）。 – RandomSeed

ref = NULL僅意味着來自p表（即product）的行不與其他行相連。這些行是您的查詢中第一個被選中的行，並且來自其他表的行將被重新連接。我總是期望EXPLAIN的第一行顯示ref = NULL。

基本上，你的執行計劃說：從products

提取行匹配WHERE條件
然後提取行從（1）在products.products_id場
products_to_categories匹配的行等了所有表

建議的附加索引：

表（列）
產品（產品，products_status）
products_specifications（products_id，規格，LANGUAGE_ID，specifications_id）
products_to_categories（products_id，categories_id）

第一一個人應該明智地幫助，我不會對其他兩個人有太多的期待。

我認爲問題在於你的很多COUNT(IF())。這是駭人聽聞的，引擎並沒有真正針對這種查詢進行優化。相反，你的目標必須是返回結果集是這樣的：

 

+---------------+-------+ 
| specification | count | 
+---------------+-------+ 
| All Season |  1 | 
+---------------+-------+ 
| Winter  | 289 | 
+---------------+-------+ 
| ...   | ... | 
+---------------+-------+

您的查詢應該是這樣的：

SELECT 
    specification, 
    COUNT(*) 
FROM products 
JOIN ... -- your current JOIN list 
GROUP BY specification -- this is the important bit

...，應該是幾乎瞬間，即使沒有額外的索引（或者products_specifications(products_id, specification)）

來源

2013-10-18 12:55:41 RandomSeed

感謝您的意見，我已將您的建議編入索引。在4546行中只有7行的status = 0，我認爲Mysql決定不使用這個索引。也是規範，計數查詢沒有多大幫助。 1.07秒對1.06秒 –

請注意，通過「'products（product_id，products_status）''我是指'product_id' **和**'products_status'上的複合索引（兩列索引）（與兩個單獨索引）。我不認爲存在這樣的索引（您的索引稱爲「products_status」，這表明索引的第一列是「product_status」）。嘗試'ALTER TABLE產品ADD INDEX pid_pstatus（product_id，product_status）'然後再次檢查您的執行計劃。但是，如果大多數產品都有'product_status = 1'，那麼這肯定是無用的。 – RandomSeed

對具有GROUP BY的版本的相同備註：首先在'products_specifications（products_id，specification）'上添加一個複合索引。 – RandomSeed

MySQL的慢大型查詢

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