小编Pho*_*nix的帖子

这是我的表，其中包含约 10,000,000 行数据

CREATE TABLE `votes` (
  `subject_name` varchar(32) COLLATE utf8_unicode_ci NOT NULL,
  `subject_id` int(11) NOT NULL,
  `voter_id` int(11) NOT NULL,
  `rate` int(11) NOT NULL,
  `updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`subject_name`,`subject_id`,`voter_id`),
  KEY `IDX_518B7ACFEBB4B8AD` (`voter_id`),
  KEY `subject_timestamp` (`subject_name`,`subject_id`,`updated_at`),
  KEY `voter_timestamp` (`voter_id`,`updated_at`),
  CONSTRAINT `FK_518B7ACFEBB4B8AD` FOREIGN KEY (`voter_id`) REFERENCES `users` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

这是索引基数

所以当我做这个查询时：

SELECT SQL_NO_CACHE * FROM votes WHERE 
    voter_id = 1099 AND 
    rate = 1 AND 
    subject_name = 'medium'
ORDER BY updated_at DESC
LIMIT …