Mysql需要很长时间才能获得更大限制

Question

我们有几个MySql查询在选择较少数量的记录时表现良好，即限制为0,100。

当我们将限制从100增加到1000，即限制为0,1000时，查询时间增加了近10倍到50倍。

EDITED 我们怎样才能优化这个？解释计划如下，

QUERY

 Select  
   concat(floor(TIMESTAMPDIFF(MINUTE,x.msgCreatedOn, NOW())/60),':',floor(TIMESTAMPDIFF(MINUTE,x.msgCreatedOn, NOW())%60)) as aging,
   x.`actionStartDate`,  
   concat(floor(TIMESTAMPDIFF(MINUTE,x.`actionStartDate`, NOW())/60),':',floor(TIMESTAMPDIFF(MINUTE,x.`actionStartDate`, NOW())%60)) as workflowAging 
from 
   (  
    Select 
        * 
    from  
        t_wk_dtls d left 
    join  t_s_dtls s  on  (d.id = s.`work_parentId` or d.`parentId` = s.`work_parentId`) and d.`currentlyActive` = true  
    left join t_w b on b.basketId=d.toBasketId  
    left join t_u u on d.toUserId= u.userId 
    left join t_s_m sch on d.sourceId=sch.schMsgId   
    left join t_l_s_a a on a.orgId='1002'  
            AND ((((a.`type`='TWITTER' and d.channel in (1,34)) 
or (a.`type`='FACEBOOK' and d.channel in (6,7)) 
or (a.`type`='GOOGLEPLUS' and d.channel in (5,25)) 
or (a.`type`='LINKEDIN' and d.channel =30) 
or (a.`type`='GOOGLEPLUS' and d.channel=36) 
or ((a.`type`='YOUTUBE' or a.`type`='GOOGLEPLUS') and d.channel=27) 
or (a.`type`='TUMBLR' and d.channel in (29,31)) 
or (a.`type`='INSTAGRAM' and d.channel=35) ) AND d.userChannelId=a.socialId)              OR (a.`type`='BLOG' and d.channel in (9,11,15,21) AND d.msgId=a.socialId)) 
     left join t_l l on l.leadId=a.leadId and l.orgId='1002' 
where 
     d.currentlyActive = true 
 and d.dataSource ='SOLR'   
 and d.profileId = '148' AND msgCreatedOn BETWEEN '2016-03-14 18:30:00' AND '2016-03-31 18:29:59'  
 order by d.msgCreatedOn desc limit 0,100000 ) as x

Answer 1

你真的需要一个子查询吗？就像现在一样，注意＆＃34;依赖子查询＆＃34;在解释结果中 - 它通常意味着子查询每返回一个外行执行一次（参见point 18.2.1.18.2 in "18.2.1.18 Subquery optimization"）。因此，随着返回更多行，您的执行时间会呈指数级增长。

既然您只是在子查询中执行select * from，那么这样的事情会不会这样做？

Select 
   concat(floor(TIMESTAMPDIFF(MINUTE,x.msgCreatedOn, NOW())/60),':',floor(TIMESTAMPDIFF(MINUTE,x.msgCreatedOn, NOW())%60)) as aging,
   x.`actionStartDate`,  
   concat(floor(TIMESTAMPDIFF(MINUTE,x.`actionStartDate`, NOW())/60),':',floor(TIMESTAMPDIFF(MINUTE,x.`actionStartDate`, NOW())%60)) as workflowAging 
from  
    t_wk_dtls d left 
join  t_s_dtls s  on  (d.id = s.`work_parentId` or d.`parentId` = s.`work_parentId`) and d.`currentlyActive` = true  
left join t_w b on b.basketId=d.toBasketId  
left join t_u u on d.toUserId= u.userId 
left join t_s_m sch on d.sourceId=sch.schMsgId   
left join t_l_s_a a on a.orgId='1002'  
        AND ((((a.`type`='TWITTER' and d.channel in (1,34)) 
or (a.`type`='FACEBOOK' and d.channel in (6,7)) 
or (a.`type`='GOOGLEPLUS' and d.channel in (5,25)) 
or (a.`type`='LINKEDIN' and d.channel =30) 
or (a.`type`='GOOGLEPLUS' and d.channel=36) 
or ((a.`type`='YOUTUBE' or a.`type`='GOOGLEPLUS') and d.channel=27) 
or (a.`type`='TUMBLR' and d.channel in (29,31)) 
or (a.`type`='INSTAGRAM' and d.channel=35) ) AND d.userChannelId=a.socialId)     OR (a.`type`='BLOG' and d.channel in (9,11,15,21) AND d.msgId=a.socialId)) 
 left join t_l l on l.leadId=a.leadId and l.orgId='1002' 
where 
 d.currentlyActive = true 
 and d.dataSource ='SOLR'   
 and d.profileId = '148' AND msgCreatedOn BETWEEN '2016-03-14 18:30:00' AND     '2016-03-31 18:29:59'  
 order by d.msgCreatedOn desc limit 0,100000;

（除了表格前缀从＆＃34; x＆＃34;更改为开头列列表中的真实前缀）