问MySQL为什么更新0行速度慢？

EN

SELECT id from content WHERE compliance_overridden = 1 AND compliance_overridden_date < DATE_SUB(NOW(), INTERVAL 30 DAY);

UPDATE content SET compliance_overridden = 0 WHERE compliance_overridden = 1 AND compliance_overridden_date < DATE_SUB(NOW(), INTERVAL 30 DAY);

CREATE TABLE `content` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) NOT NULL,
  `content_key` char(40) NOT NULL,
  `body` mediumtext,
  `original_body` mediumtext,
  `meta` mediumblob,
  `status` enum('approved','deleted','draft','library','flagged','in progress','pending','published','publishing error','queued','ready','retracted','scheduled','removed','for review','reviewed','disabled') NOT NULL DEFAULT 'in progress',
  `is_flagged` int(11) NOT NULL DEFAULT '0',
  `extraction_status` enum('queued','processing','processed','processing error') DEFAULT NULL,
  `type` enum('internal','external','library') NOT NULL DEFAULT 'internal',
  `compliance_status` enum('ok','error','warning','unchecked','fail','overridden-ok','overridden-error','queued') DEFAULT 'unchecked' COMMENT 'Status when content is reviewed against guidelines',
  `queued_for_compliance` tinyint(4) NOT NULL DEFAULT '0',
  `queued_date` timestamp NULL DEFAULT NULL,
  `review_retries` int(11) NOT NULL,
  `review_notes` varchar(255) DEFAULT NULL,
  `needs_review` tinyint(1) DEFAULT '0' COMMENT 'Indicates that the content items needs the compliance reviewed to be checked',
  `pushed_for_review` enum('no','yes','error') NOT NULL DEFAULT 'no' COMMENT 'Flags if content is pushed to Minerva.',
  `risk_score` tinyint(1) DEFAULT '0',
  `keywords` text,
  `track` varchar(60) DEFAULT NULL,
  `purpose` enum('arbitrary','compliance_file_check','compliance_text_check','document','promotion','reply','retweet','site','site_post','soa','status_update','url') NOT NULL DEFAULT 'site' COMMENT 'Changed to an enum with applicable values. This will allow us to optimise queries on this column.',
  `purpose_note` text COMMENT 'Optional note explaining the purpose of this item',
  `format` varchar(20) DEFAULT NULL,
  `media` varchar(255) DEFAULT NULL,
  `media_alternate` varchar(255) DEFAULT NULL,
  `mime_type` varchar(255) DEFAULT NULL,
  `user_id` int(11) DEFAULT NULL,
  `tag_id` int(11) DEFAULT NULL,
  `email_template_id` int(11) DEFAULT NULL,
  `social_account_id` int(11) DEFAULT NULL,
  `target_social_account_id` int(11) DEFAULT NULL,
  `parent_id` int(11) DEFAULT NULL,
  `notes` text,
  `options` text,
  `compliance_notes` text,
  `notified` tinyint(1) NOT NULL COMMENT 'Indicates if legal have been notified of the content change',
  `publish_immediately` tinyint(1) DEFAULT '0',
  `score` int(11) DEFAULT NULL,
  `insights` text,
  `publish_date` timestamp NULL DEFAULT NULL,
  `date_published` timestamp NULL DEFAULT NULL,
  `external_id` varchar(40) DEFAULT NULL,
  `feed_id` int(11) DEFAULT NULL,
  `site_id` int(11) DEFAULT NULL,
  `client_id` int(11) DEFAULT NULL,
  `has_changed` tinyint(1) DEFAULT '0' COMMENT 'Indicates if the content has ever changed',
  `was_flagged` tinyint(4) NOT NULL DEFAULT '0',
  `last_flagged` timestamp NULL DEFAULT NULL COMMENT 'Date content was last flagged',
  `compliance_overridden` tinyint(4) NOT NULL DEFAULT '0',
  `compliance_overridden_date` timestamp NULL DEFAULT NULL,
  `was_risky` tinyint(1) DEFAULT '0' COMMENT 'Indicates if the content was ever risky',
  `last_risky` timestamp NULL DEFAULT NULL COMMENT 'Date content was last assigned risk',
  `reference_urls` enum('none','ok','unchecked','error') NOT NULL DEFAULT 'none',
  `screenshot_url` text,
  `rescan` enum('no','manual-queued','compliance-changed','compliance-unchanged','compliance-unchecked') NOT NULL DEFAULT 'no',
  `rescan_rules` varchar(50) DEFAULT NULL,
  `applicable_rules` text COMMENT 'Applicable rules for a review',
  `lsh_hash` char(70) DEFAULT NULL,
  `comment_count` int(11) NOT NULL DEFAULT '0',
  `modified` timestamp NULL DEFAULT NULL,
  `created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  UNIQUE KEY `content_key` (`content_key`),
  KEY `fk_content_user` (`user_id`),
  KEY `fk_content_content` (`parent_id`),
  KEY `fk_content_email_template` (`email_template_id`),
  KEY `fk_content_target_social_account` (`social_account_id`),
  KEY `fk_content_feed` (`feed_id`),
  KEY `fk_content_site` (`site_id`),
  KEY `title` (`title`),
  KEY `status` (`status`),
  KEY `type` (`type`),
  KEY `needs_review` (`needs_review`),
  KEY `compliance_status` (`compliance_status`),
  KEY `risk_score` (`risk_score`),
  KEY `purpose` (`purpose`),
  KEY `extraction_status_idx` (`extraction_status`),
  KEY `client_id` (`client_id`),
  KEY `is_flagged_idx` (`is_flagged`),
  KEY `purpose_idx` (`purpose`),
  FULLTEXT KEY `content_index` (`title`,`body`),
  CONSTRAINT `content_ibfk_1` FOREIGN KEY (`client_id`) REFERENCES `client` (`id`),
  CONSTRAINT `fk_content_content` FOREIGN KEY (`parent_id`) REFERENCES `content` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `fk_content_feed` FOREIGN KEY (`feed_id`) REFERENCES `feed` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `fk_content_site` FOREIGN KEY (`site_id`) REFERENCES `site` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `fk_content_social_account` FOREIGN KEY (`social_account_id`) REFERENCES `social_account` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `fk_content_target_social_account` FOREIGN KEY (`social_account_id`) REFERENCES `social_account` (`id`),
  CONSTRAINT `fk_content_user` FOREIGN KEY (`user_id`) REFERENCES `user` (`user_id`)
) ENGINE=InnoDB AUTO_INCREMENT=247236 DEFAULT CHARSET=utf8