@H_502_1@我有一个大约9GB的Azure sql数据库.它提供一个Web应用程序,每小时处理大约135K请求.大多数数据都是短暂的,它会在几分钟到五天内存放在数据库中并被删除.每天大约10GB通过数据库移动.
我试图在表上运行删除查询,从350,000条记录中删除约250,000条记录.大约10％的记录有一个或两个nvarchar(max)值足够大,可以存储在LOB存储中.
在周末,我试图一次删除它们.它在我取消查询之前运行了四个小时,然后它又回来了8个小时 – 糟糕的举动.我真的没想到它会那么糟糕.
然后我尝试了另一种方法.这个批处理在晚上运行,当时Web应用程序每小时处理大约100K请求. tblJobs Id字段是唯一标识符,它是主键.
insert @tableIds select Id from dbo.tblJobs with(nolock)
where (datediff(day,SchedDate,getDate()) > 60)
or (datediff(day,ModifiedDate,getDate()) > 3 and ToBeRemoved = 1)
set @maintLogStr = 'uspMaintenance [tblJobs] Obsolete J records count @tableIds: ' + convert(nvarchar(12),(select count(1) from @tableIds))
insert dbo.admin_MaintenanceLog(LogEntry) values(@maintLogStr)
set @maintLogId = newid()
set @maintLogStr = 'uspMaintenance [tblJobs] Obsolete J records beginning loop...'
insert dbo.admin_MaintenanceLog(Id,LogEntry) values(@maintLogId,@maintLogStr)
while exists(select * from @tableIds)
begin
delete @tableIdsTmp
begin transaction
insert @tableIdsTmp select top 1000 id from @tableIds
delete p from @tableIdsTmp i join dbo.tblJobs p on i.id = p.Id
delete x from @tableIdsTmp t join @tableIds x on t.id = x.id
set @maintLogStr = 'uspMaintenance [tblJobs] Obsolete J records remaining count @tableIds: ' + convert(nvarchar(12),(select count(1) from @tableIds))
update dbo.admin_MaintenanceLog set LogEntry = @maintLogStr,RecordCreated = getdate() where Id = @maintLogId
commit transaction
if @dowaits = 1 WAITFOR DELAY '00:00:01.000'
end
SchedDate,ModifiedDate和ToBeRemoved没有编入索引,因此在@tableIds中收集ID大约需要3分钟 – 不错.
然后从日志条目中花费1小时55分钟从tblJobs中删除11,000条记录,此时从远程计算机调用的作业超时.
为什么需要这么长时间？我该怎么做才能加快速度？
