针对海量数据优化MySQL全外连接

Question

我们有以下 mysql 表（为了直奔主题而简化）

CREATE TABLE `MONTH_RAW_EVENTS` (
  `idEvent` int(11) unsigned NOT NULL,
  `city` varchar(45) NOT NULL,
  `country` varchar(45) NOT NULL,
  `ts` datetime NOT NULL,
  `idClient` varchar(45) NOT NULL,
  `event_category` varchar(45) NOT NULL,
  ... bunch of other fields
  PRIMARY KEY (`idEvent`),
  KEY `idx_city` (`city`),
  KEY `idx_country` (`country`),
  KEY `idClient` (`idClient`),
) ENGINE=InnoDB;

CREATE TABLE `compilation_table` (
  `idClient` int(11) unsigned DEFAULT NULL,
  `city` varchar(200) DEFAULT NULL,
  `month` int(2) DEFAULT NULL,
  `year` int(4) DEFAULT NULL,
  `events_profile` int(10) unsigned NOT NULL DEFAULT '0',
  `events_others` int(10) unsigned NOT NULL DEFAULT '0',
  `events_total` int(10) unsigned NOT NULL DEFAULT '0',
  KEY `idx_month` (`month`),
  KEY `idx_year` (`year`),
  KEY `idx_idClient` (`idClient`),
  KEY `idx_city` (`city`)
) ENGINE=InnoDB;

MONTH_RAW_EVENTS包含近 20M 行，用户在网站中执行操作，大小近 4GB

compilation_table每个月都有一个客户/城市摘要，我们用它在网站上实时显示统计数据

我们每月处理一次统计信息（从第一个表到第二个表），并且我们正在尝试优化执行此类操作的查询（因为到目前为止，我们正在 PHP 中处理所有内容，这需要很长时间）

这是我们提出的查询，它似乎在使用小数据子集时完成了工作，处理完整数据集需要超过 6 个小时的时间

INSERT INTO compilation_table (idClient,city,month,year,events_profile,events_others)


    SELECT  IFNULL(OTHERS.idClient,AP.idClient) as idClient,
            IF(IFNULL(OTHERS.city,AP.city)='','Others',IFNULL(OTHERS.city,AP.city)) as city,
        01,2014,
    IFNULL(AP.cnt,0) as events_profile,
        IFNULL(OTHERS.cnt,0) as events_others           

    FROM
    (
        SELECT idClient,CONCAT(city,', ',country) as city,count(*) as cnt 
        FROM `MONTH_RAW_EVENTS` WHERE `ts`>'2014-01-01 00:00:00' AND `ts`<='2014-01-31 23:59:59'
        AND `event_category`!='CLIENT PROFILE'
        GROUP BY idClient,city
    ) as OTHERS
 LEFT JOIN 
    (
        SELECT idClient,CONCAT(city,', ',country) as city,count(*) as cnt 
        FROM `MONTH_RAW_EVENTS` WHERE `ts`>'2014-01-01 00:00:00' AND `ts`<='2014-01-31 23:59:59'
        AND `event_category`='CLIENT PROFILE'
        GROUP BY idClient,city
    ) as CLIPROFILE 
    ON CLIPROFILE.city=OTHERS.city and CLIPROFILE.idClient=OTHERS.idClient

 UNION

    SELECT  IFNULL(OTHERS.idClient,CLIPROFILE.idClient) as idClient,
            IF(IFNULL(OTHERS.city,CLIPROFILE.city)='','Others',IFNULL(OTHERS.city,CLIPROFILE.city)) as city,
            01,2014,
            IFNULL(CLIPROFILE.cnt,0) as events_profile,
            IFNULL(OTHERS.cnt,0) as events_others           
    FROM
    (
        SELECT idClient,CONCAT(city,', ',country) as city,count(*) as cnt 
        FROM `MONTH_RAW_EVENTS` WHERE `ts`>'2014-01-01 00:00:00' AND `ts`<='2014-01-31 23:59:59'
        AND `event_category`!='CLIENT PROFILE'
        GROUP BY idClient,city
    ) as OTHERS
 RIGHT JOIN 
    (
        SELECT idClient,CONCAT(city,', ',country) as city,count(*) as cnt 
        FROM `MONTH_RAW_EVENTS` WHERE `ts`>'2014-01-01 00:00:00' AND `ts`<='2014-01-31 23:59:59'
        AND `event_category`='CLIENT PROFILE'
        GROUP BY idClient,city
    ) as CLIPROFILE 
    ON CLIPROFILE.city=OTHERS.city and CLIPROFILE.idClient=OTHERS.idClient

我们正在尝试做的是 Mysql 中的 FULL Outer Join，因此查询的基本模式如下：此处建议的模式

我们如何优化查询？我们一直在尝试不同的索引，不断地改变东西，但8小时后仍然没有完成运行，

MySQL服务器是Percona MySQL 5.5专用机器，具有2cpu、2GB RAM和SSD磁盘，我们使用Percona工具优化了此类服务器的配置，

任何帮助将非常感激，

谢谢

Answer 1

您正在执行 UNION，这会导致 DISTINCT 处理。

通常最好将 Full Join 重写为 Left Join 加上 Right Join 的不匹配行（如果是正确的 1:n join）

OTHERS LEFT JOIN CLIPROFILE 
ON CLIPROFILE.city=OTHERS.city and CLIPROFILE.idClient=OTHERS.idClient
union all
OTHERS RIGHT JOIN CLIPROFILE 
ON CLIPROFILE.city=OTHERS.city and CLIPROFILE.idClient=OTHERS.idClient
WHERE OTHERS.idClient IS NULL 

另外，您可能会在连接临时表之前将派生表的结果具体化，因此计算只完成一次（我不知道MySQL的优化器是否足够聪明，可以自动执行此操作）。

另外，将城市/国家作为单独的列进行分组和连接，并在外部步骤中将CONCAT(city,', ',country) 作为城市执行，可能会更有效。