mysql - 缓慢的初始 mysql 查询

Question

运行 Mysql V5.6.22，在正确索引的数据库上运行复杂查询，最初的响应时间非常慢（10 秒）。随后的查询（针对不同的项目）响应速度非常快（50 毫秒）。所以我猜查询缓存正在做他们的工作——但是我如何最小化最初的慢响应？

该数据库是一个外部维护的医学数据库（SNOMED），我对当前快照使用推荐的视图——我认为这些视图是速度的限制。

奇怪的是重新启动 mysql 并没有什么不同——这似乎是一个时间问题——如果数据库在一段时间内没有使用，那么启动需要很长时间。

所以我的问题是，是否有一个 mysql 设置用于这些缓存的保留时间，或者我应该使用不同的方法而不使用视图（SNOMED 的数据每年更新 2 次，在另一个类似的药物数据库中有每月发布。？

你们中的一些人希望看到查询，所以就到这里。警告它确实有点棘手，基本查询的行数在评论中给出...... ;-)

SELECT DISTINCT concat(c.id, '::', c.effectiveTime) as id, `d1`.`term` as label, `d2`.`term`
FROM (`snomed`.`rf2_ss_refset` as refset)
JOIN `snomed`.`rf2_ss_concepts` as c ON `c`.`id` = `refset`.`referencedCOmponentId`
JOIN `snomed`.`rf2_ss_descriptions` as d1 ON `d1`.`conceptId` = `refset`.`referencedComponentId`
JOIN `snomed`.`rf2_ss_descriptions` as d2 ON `d2`.`conceptId` = `d1`.`conceptId`
JOIN `snomed`.`rf2_ss_language_refset` as lang ON `lang`.`referencedComponentId` = `d1`.`id`
WHERE `refset`.`refSetId` =  32570071000036102
AND `refset`.`active` =  1
AND `d2`.`typeId` =  900000000000013009
AND `d1`.`active` =  1
AND `d2`.`active` =  1
AND `d1`.`moduleId` =  900000000000207008
AND `d2`.`moduleId` =  900000000000207008
AND `lang`.`active` =  1
AND `lang`.`acceptabilityId` =  900000000000548007
AND `d2`.`term` like "hypertension%"
ORDER BY `d1`.`term`, `d2`.`term`

在哪里：

CREATE TABLE `rf2_ss_refset` (
  `id` char(36) COLLATE utf8_unicode_ci NOT NULL,
  `effectiveTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `active` smallint(1) NOT NULL,
  `moduleId` bigint(20) unsigned NOT NULL,
  `refSetId` bigint(20) unsigned NOT NULL,
  `referencedComponentId` bigint(20) unsigned NOT NULL,
  PRIMARY KEY (`id`,`effectiveTime`),
  KEY `moduleId_idx` (`moduleId`),
  KEY `refSetId_idx` (`refSetId`),
  KEY `referencedComponentId_idx` (`referencedComponentId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

CREATE ALGORITHM=UNDEFINED DEFINER=`snomed`@`localhost` SQL SECURITY DEFINER VIEW `rf2_ss_concepts`
AS SELECT
   `t1`.`id` AS `id`,
   `t1`.`effectiveTime` AS `effectiveTime`,
   `t1`.`active` AS `active`,
   `t1`.`moduleId` AS `moduleId`,
   `t1`.`definitionStatusId` AS `definitionStatusId`
FROM `rf2_full_concepts` `t1` where (`t1`.`effectiveTime` = (select max(`t2`.`effectiveTime`) from `rf2_full_concepts` `t2` where (`t1`.`id` = `t2`.`id`)));

CREATE ALGORITHM=UNDEFINED DEFINER=`snomed`@`localhost` SQL SECURITY DEFINER VIEW `rf2_ss_descriptions`
AS SELECT
   `t1`.`id` AS `id`,
   `t1`.`effectiveTime` AS `effectiveTime`,
   `t1`.`active` AS `active`,
   `t1`.`moduleID` AS `moduleID`,
   `t1`.`conceptId` AS `conceptId`,
   `t1`.`languageCode` AS `languageCode`,
   `t1`.`typeID` AS `typeID`,
   `t1`.`term` AS `term`,
   `t1`.`caseSignificanceId` AS `caseSignificanceId`
FROM `rf2_full_descriptions` `t1` where (`t1`.`effectiveTime` = (select max(`t2`.`effectiveTime`) from `rf2_full_descriptions` `t2` where (`t1`.`id` = `t2`.`id`)));

CREATE ALGORITHM=UNDEFINED DEFINER=`snomed`@`localhost` SQL SECURITY DEFINER VIEW `rf2_ss_language_refset`
AS SELECT
   `t1`.`id` AS `id`,
   `t1`.`effectiveTime` AS `effectiveTime`,
   `t1`.`active` AS `active`,
   `t1`.`moduleId` AS `moduleId`,
   `t1`.`refSetId` AS `refSetId`,
   `t1`.`referencedComponentId` AS `referencedComponentId`,
   `t1`.`acceptabilityId` AS `acceptabilityId`
FROM `rf2_full_language_refset` `t1` where (`t1`.`effectiveTime` = (select max(`t2`.`effectiveTime`) from `rf2_full_language_refset` `t2` where (`t1`.`id` = `t2`.`id`)));

CREATE ALGORITHM=UNDEFINED DEFINER=`snomed`@`localhost` SQL SECURITY DEFINER VIEW `rf2_ss_relationships`
AS SELECT
   `t1`.`id` AS `id`,
   `t1`.`effectiveTime` AS `effectiveTime`,
   `t1`.`active` AS `active`,
   `t1`.`moduleId` AS `moduleId`,
   `t1`.`sourceId` AS `sourceId`,
   `t1`.`destinationId` AS `destinationId`,
   `t1`.`relationshipGroup` AS `relationshipGroup`,
   `t1`.`typeId` AS `typeId`,
   `t1`.`characteristicTypeId` AS `characteristicTypeId`,
   `t1`.`modifierId` AS `modifierId`
FROM `rf2_full_relationships` `t1` where (`t1`.`effectiveTime` = (select max(`t2`.`effectiveTime`) from `rf2_full_relationships` `t2` where (`t1`.`id` = `t2`.`id`)));

#select count(*) from rf2_full_concepts # 507046
CREATE TABLE `rf2_full_concepts` (
  `id` bigint(20) unsigned NOT NULL,
  `effectiveTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `active` tinyint(4) DEFAULT NULL,
  `moduleId` bigint(20) unsigned NOT NULL,
  `definitionStatusId` bigint(20) unsigned NOT NULL,
  PRIMARY KEY (`id`,`effectiveTime`),
  KEY `moduleId_idx` (`moduleId`),
  KEY `definitionStatusId_idx` (`definitionStatusId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

#select count(*) from rf2_full_descriptions # 1486373
CREATE TABLE `rf2_full_descriptions` (
  `id` bigint(20) unsigned NOT NULL,
  `effectiveTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `active` tinyint(4) DEFAULT NULL,
  `moduleID` bigint(20) unsigned NOT NULL,
  `conceptId` bigint(20) unsigned NOT NULL,
  `languageCode` char(2) COLLATE utf8_unicode_ci NOT NULL DEFAULT 'en',
  `typeID` bigint(20) unsigned NOT NULL,
  `term` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
  `caseSignificanceId` bigint(20) unsigned NOT NULL,
  PRIMARY KEY (`id`,`effectiveTime`),
  KEY `moduleID_idx` (`moduleID`),
  KEY `conceptId_idx` (`conceptId`),
  KEY `typeID_idx` (`typeID`),
  KEY `caseSignificanceId_idx` (`caseSignificanceId`),
  KEY `term_idx` (`term`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

#select count(*) from rf2_full_relationships = 4582286 
CREATE TABLE `rf2_full_relationships` (
  `id` bigint(20) unsigned NOT NULL,
  `effectiveTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `active` tinyint(4) DEFAULT '1',
  `moduleId` bigint(20) unsigned NOT NULL,
  `sourceId` bigint(20) unsigned NOT NULL,
  `destinationId` bigint(20) unsigned NOT NULL,
  `relationshipGroup` bigint(20) unsigned NOT NULL,
  `typeId` bigint(20) unsigned NOT NULL,
  `characteristicTypeId` bigint(20) unsigned NOT NULL,
  `modifierId` bigint(20) unsigned NOT NULL,
  PRIMARY KEY (`id`,`effectiveTime`),
  KEY `moduleId_idx` (`moduleId`),
  KEY `sourceId_idx` (`sourceId`),
  KEY `destinationId_idx` (`destinationId`),
  KEY `relationshipGroup_idx` (`relationshipGroup`),
  KEY `typeId_idx` (`typeId`),
  KEY `characteristicTypeId_idx` (`characteristicTypeId`),
  KEY `modifierId_idx` (`modifierId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

#select count(*) from rf2_full_language_refset # 624467
CREATE TABLE `rf2_full_language_refset` (
  `id` char(36) COLLATE utf8_unicode_ci NOT NULL,
  `effectiveTime` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `active` smallint(1) NOT NULL,
  `moduleId` bigint(20) unsigned NOT NULL,
  `refSetId` bigint(20) unsigned NOT NULL,
  `referencedComponentId` bigint(20) unsigned NOT NULL,
  `acceptabilityId` bigint(20) unsigned NOT NULL,
  PRIMARY KEY (`id`,`effectiveTime`),
  KEY `moduleId` (`moduleId`),
  KEY `refSetId` (`refSetId`),
  KEY `referencedComponentId` (`referencedComponentId`),
  KEY `acceptabilityId` (`acceptabilityId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

score 2 · Accepted Answer

在没有所有部分的情况下诊断别人的服务器是很困难的，所以我会做出以下假设（如果我错了，请纠正我）：

这不是在 DB 级服务器上运行的
MySQL 配置尚未特别配置为此任务

对于您展示的示例，您的表看起来索引过度，并且由于数据集很大，我可以想象最大的索引文件太大而无法放入 MySQL 的索引缓存中。

如果没有有关环境的更多信息，您描述的行为似乎取决于配置的缓冲区。此时，操作系统会介入并在内存中缓冲 DB。

当您重新启动 MySQL 时，它会快速查询，因为操作系统仍将文件保存在其缓冲区中。当您停止访问数据库时，操作系统最终将取消缓冲文件，您将回到缓慢的初始查询。

我在超过配置的缓冲区大小的大型索引上看到了相同的行为，但这是一组更大的数据。将数据库配置为具有更大的索引和表数据缓冲区解决了我的特殊问题。就我而言，查询速度从 10-15 秒下降到毫秒。

http://dev.mysql.com/doc/refman/5.6/en/innodb-parameters.html#sysvar_innodb_buffer_pool_size

如果您有一些空闲 RAM，请尝试稍微增加缓冲池大小。默认大小为 128Mb，您最大的索引文件大约为 279Mb（64 字节 * 4,582,286 行）。首先，尝试将配置中的值设置为 512Mb。重启，重新测试。如果它仍然不是很好，添加另一个 128Mb 并重复，直到它工作。如果此数据库位于专用机器上，则根据您的设置，将值设置得相当高（总 RAM 的 50-75%）应该是安全的。

一个快速的谷歌想出了一个很好的指南，关于要摆弄什么配置值。 http://www.tocker.ca/2013/09/17/what-to-tune-in-mysql-56-after-installation.html

mysql - 缓慢的*初始* mysql 查询

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mysql - 缓慢的初始 mysql 查询