降低逻辑读取



我使用的是stackoverflow2013数据库,我的查询是

select p.CreationDate, p.title,
c.Text,
c.Score
from comments c join posts p on c.PostId = p.id
where p.CreationDate between ‘2008-08-29 00:00:00’ and ‘2008-09-02 23:59:58’ order by c.score desc

在创建索引之前,我得到了以下信息——执行时间为18分26秒

(2055 rows affected)
Table ‘Worktable’. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table ‘Workfile’. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table ‘Comments’. Scan count 1, logical reads 1028410, physical reads 4, read-ahead reads 1027512, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table ‘Posts’. Scan count 1, logical reads 4184557, physical reads 0, read-ahead reads 4178310, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

然后我去创建了以下索引

create index forcomments on dbo.comments(postid asc ,  Score desc) include (text)
create index forposts on dbo.posts(creationdate asc) include (title)

创建这个之后,查询的性能是惊人的。总执行时间现在为0秒。

(2055 rows affected)
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Comments'. Scan count 4536, logical reads 19562, physical reads 0, read-ahead reads 1, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Posts'. Scan count 1, logical reads 26, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

我想问一下,我们如何才能使逻辑读取比我们更低已经有了?

要点-统计数据是最新的,在执行计划分析中没有观察到不正确的基数。

我想问一下,我们如何才能使逻辑读取比现有的更低?

唯一的方法是使用索引视图来实现联接。

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