分析问题
将数据库备份到一台测试的服务器上，查看一下数据库的数据文件和日志文件情况，发现日志文件比较大，貌似这也是一个SQL Server 存在的问题，具体原因不清楚，但是解决方法已经非常成熟，该问题暂时不影响使用，先不管它。
上一篇定位了问题，找出了多条Top SQL，其中这条最过分。
exec oa_SWLIST
’glzyf’,
’(s.fileSerialNumber like ’’%%’’ or s.title like ’’%%’’ or s.keywords like ’’%%’’ or s.fileZi like ’’%%’’) and ’,
’ ( ft.userid=’’glzyf’’ ) ’
分析一下这个存储过程，我习惯是先看看SQL语句的结构，而不是马上看执行计划，或者直接跑语句获得统计信息。
ALTER PROCEDURE [dbo].[oa_SWLIST]
@userID varchar(20),
@sql varchar(1000),
@userIDs varchar(1000)
AS
DECLARE @SQL1 nchar(4000) ;
DECLARE @SQL2 nchar(4000) ;
create table #employees(
[id] [int] IDENTITY(1,1) NOT NULL,parentId int,pkId int,status int,title nvarchar(1500),comeOrg nvarchar(100),
fileDate DateTime,fileName nvarchar(4000),filePath nvarchar(4000),readStatus nvarchar(10),optionStatus nvarchar(10),
depId nvarchar(20),urgencyLevel nvarchar(10));
set @SQL1=’insert into #employees (parentId,pkId,status,title,comeOrg,fileDate,fileName,filePath,readStatus,optionStatus,depId,urgencyLevel)
select distinct s.parentId,s.pkId,0,s.title,s.comeOrg,s.fileDate,
s.fileName,s.filePath,ft.readStatus,0,s.remark3,
case
when urgencyLevel=’’普通’’ then 0
when urgencyLevel=’’急件’’ then 1
when urgencyLevel=’’特办’’ then 2
when urgencyLevel=’’特急件’’ then 3
when urgencyLevel=’’限时’’ then 4
else 0
end as urgencyLevel
from ShouWen as s ,
FlowTurning as ft where ’+@sql+’ ft.status=0 and ft.type=’’sw’’
and s.pkid=ft.pkid and s.status<>’’4’’ and ’+@userIDs+’ order by urgencyLevel desc,s.filedate desc’
set @SQL2=’insert into #employees (parentId,pkId,status,title,comeOrg,fileDate,
fileName,filePath,readStatus,optionStatus,depId,urgencyLevel)
select distinct s.parentId,s.pkId,1,s.title,s.comeOrg,s.fileDate,
s.fileName,s.filePath,1,l.optionstatus,s.remark3,urgencyLevel
from shouwen as s, log as l where ’+@sql+’ s.status<>’’4’’ and s.pkid in
(
select distinct(mid) from log where uid=’’’+@userID+’’’ and typeid=’’shouwen’’
)and l.mid=s.pkid and uid=’’’+@userID+’’’ and typeid=’’shouwen’’
order by s.fileDate desc’
print (@SQL1);
exec (@SQL1)
print (’+++++++++++++++++++++++++++++++++++’);
print (@SQL2);
exec (@SQL2)
select * from #employees
delete from #employees
从结果来看该存储过程其实就是执行了两条动态SQL，分别存在@SQL1和SQL2。稍微修改了一下存储过程，加入了一些调试信息，打开统计器。
SET STATISTICS IO on;
SET STATISTICS TIME on;
执行存储过程，这里由于信息量比较大。
可见@SQL1的语句耗时并不多，@SQL2资源占用是非常厉害的。其中 Log 表扫描530次，这个表的数据量有257417条，说大不大，说小也不小了，而且还得扫描530次，唉，啥也不说了，而shouwen这张表就小很多也有25000+条记录。#p#分页标题#e#
我将@SQL2的语句整理出来，去掉那个讨厌的 insert into #employees。
select distinct s.parentId,s.pkId,1,s.title,s.comeOrg,s.fileDate,
s.fileName,s.filePath,1,l.optionstatus,s.remark3,urgencyLevel
from shouwen as s,
log as l
where
(s.fileSerialNumber like ’%%’ or s.title like ’%%’
or s.keywords like ’%%’ or s.fileZi like ’%%’)
and s.status<>’4’
and s.pkid in
(select distinct(mid) from log where uid=’glzyf’ and typeid=’shouwen’)
and l.mid=s.pkid and uid=’glzyf’ and typeid=’shouwen’
order by s.fileDate desc
看看这个select 语句的执行计划啦。
以下才是重点，两个在Log表上面的“聚集索引扫描”：
无论哪个RDBMS的语句调优，绝大部分的情况下都是将执行计划中的“扫描”转变为“查找”。
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