MySQL表 - 性能，指標數

Question

我有表，這種結構：

CREATE TABLE `supplies` (
`cycle_id` int(11) NOT NULL, 
`subject_id` varchar(45) COLLATE utf8_unicode_ci NOT NULL, 
`market_id` int(11) NOT NULL, 
`price` int(11) NOT NULL, 
`currency_id` varchar(45) COLLATE utf8_unicode_ci DEFAULT NULL, 
`offered_order` bigint(20) DEFAULT NULL, 
PRIMARY KEY (`subject_id`,`market_id`,`cycle_id`,`price`), 
KEY `fk_supplies_subjects` (`subject_id`), 
KEY `fk_supplies_markets` (`market_id`), 
KEY `fk_supplies_currencies` (`currency_id`), 
CONSTRAINT `fk_supplies_currencies` FOREIGN KEY (`currency_id`) REFERENCES `currencies` (`currency_id`) ON DELETE CASCADE ON UPDATE CASCADE, 
CONSTRAINT `fk_supplies_subjects` FOREIGN KEY (`subject_id`) REFERENCES `subjects` (`subject_id`) ON DELETE CASCADE ON UPDATE CASCADE, 
CONSTRAINT `fk_supplies_markets` FOREIGN KEY (`market_id`) REFERENCES `markets` (`market_id`) ON DELETE CASCADE ON UPDATE CASCADE 
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci 

表有大約20000行。我的表現有問題。我日誌記錄正在服用時間長的SQL查詢和從日誌中我可以看到：

1. 慢INSERT s轉換表。

   INSERT INTO supplies VALUES (11, 'userName', 18, 30, 'pound', 20) ; 
   

2. 從錶慢DELETE小號

   DELETE FROM supplies WHERE cycle_id = 6 AND market_id = 18 AND subject_id = 'userName' ; 
   

我能怎麼改善？

我想，改變索引會有所幫助，因爲PRIMARY鍵是由4列組成（有些甚至是varchars）。但我應該如何更改索引？

謝謝大家。

Answer 1

您應該只創建一個只有一個字段的主鍵。這是基本的性能優化

CREATE TABLE `supplies` (
`supplies_id` int(11) NOT NULL AUTO_INCREMENT, 
`cycle_id` int(11) NOT NULL, 
`subject_id` varchar(45) COLLATE utf8_unicode_ci NOT NULL, 
`market_id` int(11) NOT NULL, 
`price` int(11) NOT NULL, 
`currency_id` varchar(45) COLLATE utf8_unicode_ci DEFAULT NULL, 
`offered_order` bigint(20) DEFAULT NULL, 
PRIMARY KEY (`supplies_id`), 
INDEX `index` (`subject_id` ASC,`market_id` ASC,`cycle_id` ASC,`price` ASC)) 
KEY `fk_supplies_subjects` (`subject_id`), 
KEY `fk_supplies_markets` (`market_id`), 
KEY `fk_supplies_currencies` (`currency_id`), 
CONSTRAINT `fk_supplies_currencies` FOREIGN KEY (`currency_id`) REFERENCES `currencies` (`currency_id`) ON DELETE CASCADE ON UPDATE CASCADE, 
CONSTRAINT `fk_supplies_subjects` FOREIGN KEY (`subject_id`) REFERENCES `subjects` (`subject_id`) ON DELETE CASCADE ON UPDATE CASCADE, 
CONSTRAINT `fk_supplies_markets` FOREIGN KEY (`market_id`) REFERENCES `markets` (`market_id`) ON DELETE CASCADE ON UPDATE CASCADE 
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci 

另一種可能的改進是可以去除級聯約束。檢查他們是否真的有必要。