MySQL的性能非常差_Mysql_Sql_Database_Performance_Distinct

MySQL的性能非常差

mysql sql database performance

MySQL的性能非常差,mysql,sql,database,performance,distinct,Mysql,Sql,Database,Performance,Distinct,我有一个具有多个左连接的独特Select语句，当where子句很大时，该语句的性能很差。以下是我的发言 SELECT DISTINCT u.*, ri.id as reg_id, d.id as dist_id FROM users u LEFT JOIN earned_points ep ON u.id = ep.user_id LEFT JOIN distributors d ON d.id = ep.distributor_id OR d.id

我有一个具有多个左连接的独特Select语句，当where子句很大时，该语句的性能很差。以下是我的发言

SELECT  DISTINCT u.*, ri.id as reg_id, d.id as dist_id
    FROM  users u
    LEFT JOIN  earned_points ep ON u.id = ep.user_id
    LEFT JOIN  distributors d ON d.id = ep.distributor_id
      OR  d.id = u.distributor_id
      OR  d.id = u.additional_distributor_id
    LEFT JOIN  registration_items_users riu ON u.id = riu.user_id
      AND  riu.distributor_id = d.id
      AND  riu.registration_item_id = 21
    LEFT JOIN  registration_items ri ON riu.registration_item_id = ri.id
    WHERE  d.id IN (201,281,321,631,901,971,1211,1601,1611,1621,
               1631,1641,1651,1661,1671,1681,1691,1701,1711,1721,1731,
               1741,1751,1761,1771,1781,2281,2291,2401,2781,2801,2931 );

此查询的解释如下：

完成此查询大约需要4秒钟。如果我把where降到一个id，那么它的速度将提高到170ms左右

如果您能就如何加快查询速度提出建议，我们将不胜感激

多谢各位

编辑

我能够根据里克·詹姆斯（接受答案）的建议提出解决方案。使用Union并去掉左连接和Distinct就成功了。与上面的4秒版本相比，这个新查询大约需要200毫秒

(SELECT  u.*, 
   (SELECT riu.registration_item_id 
       FROM registration_items_users riu 
       WHERE riu.user_id = u.id 
           AND riu.distributor_id = d.id 
           AND riu.registration_item_id = 21) as reg_id,
   d.id as dist_id
   FROM users u
   JOIN earned_points ep ON u.id = ep.user_id
   JOIN distributors d ON d.id = ep.distributor_id
       WHERE d.id IN (201,281,321,631,901,971,1211,1601,1611,1621,
            1631,1641,1651,1661,1671,1681,1691,1701,1711,1721,1731,
            1741,1751,1761,1771,1781,2281,2291,2401,2781,2801,2931))
   UNION
(SELECT  u.*, 
   (SELECT riu.registration_item_id 
       FROM registration_items_users riu 
       WHERE riu.user_id = u.id 
           AND riu.distributor_id = d.id 
           AND riu.registration_item_id = 21) as reg_id,
   d.id as dist_id
   FROM users u
   JOIN distributors d ON d.id = u.distributor_id
       WHERE d.id IN (201,281,321,631,901,971,1211,1601,1611,1621,
            1631,1641,1651,1661,1671,1681,1691,1701,1711,1721,1731,
            1741,1751,1761,1771,1781,2281,2291,2401,2781,2801,2931))
   UNION
(SELECT  u.*, 
   (SELECT riu.registration_item_id 
       FROM registration_items_users riu 
       WHERE riu.user_id = u.id 
           AND riu.distributor_id = d.id 
           AND riu.registration_item_id = 21) as reg_id,
   d.id as dist_id
   FROM users u
   JOIN distributors d ON d.id = u.additional_distributor_id
       WHERE d.id IN (201,281,321,631,901,971,1211,1601,1611,1621,
            1631,1641,1651,1661,1671,1681,1691,1701,1711,1721,1731,
            1741,1751,1761,1771,1781,2281,2291,2401,2781,2801,2931))

在

EXPLAIN

中，查看

行。它正在对大约6974行进行“表扫描”

除非“right”表是可选的，否则不要使用

LEFT

将

或

变为

接头

；这就是索引让你失望的地方。（

UNION ALL

比

UNION DISTINCT

快；选择有意义的一个。）

假设可以删除

左侧

，并假设

独立

可以从

选择

移动到

联合

：

SELECT  u.*, ri.id as reg_id, d.id as dist_id
    FROM  users u
    JOIN  earned_points ep ON u.id = ep.user_id  -- ep needed only for this
    JOIN  distributors d ON d.id = ep.distributor_id  -- This one line differs
    JOIN  registration_items_users riu ON u.id = riu.user_id
      AND  riu.distributor_id = d.id
      AND  riu.registration_item_id = 21
    JOIN  registration_items ri ON riu.registration_item_id = ri.id
    WHERE  d.id IN (201,281,321,631,901,971,1211,1601,1611,1621,
                1631,1641,1651,1661,1671,1681,1691,1701,1711,1721,1731,
                1741,1751,1761,1771,1781,2281,2291,2401,2781,2801,2931 
                   )
    UNION  DISTINCT 
SELECT  u.*, ri.id as reg_id, d.id as dist_id
    FROM  users u
    JOIN  distributors d ON d.id = u.distributor_id
    JOIN  registration_items_users riu ON u.id = riu.user_id
      AND  riu.distributor_id = d.id
      AND  riu.registration_item_id = 21
    JOIN  registration_items ri ON riu.registration_item_id = ri.id
    WHERE  d.id IN (201,281,321,631,901,971,1211,1601,1611,1621,
                1631,1641,1651,1661,1671,1681,1691,1701,1711,1721,1731,
                1741,1751,1761,1771,1781,2281,2291,2401,2781,2801,2931 
                   )
    UNION  DISTINCT 
SELECT  u.*, ri.id as reg_id, d.id as dist_id
    FROM  users u
    JOIN  distributors d ON d.id = u.additional_distributor_id
    JOIN  registration_items_users riu ON u.id = riu.user_id
      AND  riu.distributor_id = d.id
      AND  riu.registration_item_id = 21
    JOIN  registration_items ri ON riu.registration_item_id = ri.id
    WHERE  d.id IN (201,281,321,631,901,971,1211,1601,1611,1621,
                1631,1641,1651,1661,1671,1681,1691,1701,1711,1721,1731,
                1741,1751,1761,1771,1781,2281,2291,2401,2781,2801,2931 
                   ) ;

通常，在列之间展开数组不是一个好主意。这似乎就是

分销商的情况。而这场混乱可能就是这样的结果
编辑
更好的方法是将ri
和rui
从selects中取出，并将其转换为子查询。这里是要点；我没有精力写这一切：
SELECT x.*,
        ( SELECT ... ri and rui stuff ... ) AS reg_id
    FROM (
        --  from above, less the ri and rui stuff:
        SELECT ...
        UNION DISTINCT
        SELECT ...
        UNION DISTINCT
        SELECT ...
         ) AS x;

这不是意料之中的事吗？列表中有32个ID。32*170毫秒=5440毫秒。所以它的执行速度比线性的稍快。也就是说，IN（）运算符可能会很慢。你可以尝试将ID列表转储到一个临时表中，加入临时表并在表上创建索引。我以前没做过临时表格。你能给我指一下正确的方向吗？ThanksI会先尝试索引，它们可以让临时表mootI觉得我已经拥有了所有表所需的索引。你对我遗漏的东西有什么建议吗？你有什么索引？您应该查看执行计划，以获得有关所需索引的提示。这是非常棒的东西！左连接是必需的。我将采纳你的建议，等我想出办法时再看一看。我会让你知道结果的。谢谢，你给我指明了正确的方向。我能够接受你所说的，并提出一个更快的问题。我能够删除所有左连接和独立连接。我将用我的查询更新我的问题，并将您的答案标记为已接受的解决方案。非常感谢。