Question

我有这种结构的表格：

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

表有大约20,000行。我的表现有问题。我正在记录需要很长时间的SQL查询，并且从日志中我可以看到：

将INSERT放慢到表格中。

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

从表

中缓慢DELETE

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

我可以改善什么？

我想，更改索引会有所帮助，因为PRIMARY键由4列组成（有些甚至是varchars）。但是我该如何更改索引呢？

谢谢大家。

Answer 1

您应该只使用一个字段创建主键。这是一项基本的性能优化

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

另一种可能的改进可以是删除级联约束。检查它们是否真的有必要。

MySQL表 - 性能，索引计数

1 个答案: