您如何解释SQL Server执行计划结果

Question

我网站上的网页运行缓慢。我已经确定这是由于下面的查询：

select distinct top 500 j.correlationid, j.timestamp
from jobs as j
inner join status as s
on j.statusid = s.id
inner join tasks as t
on j.taskid = t.id
inner join processes as p
on t.processid = p.id
where j.viewable = 1
and p.[group] = 'SapDocument'
and s.name in ('Dead', 'Process Complete') 
order by j.timestamp desc

我已经运行了估计执行计划，但我不确定如何解释。我希望有人可以帮我解释。我想我可能需要一个索引。非常感谢任何提示！