Home Database Mysql Tutorial SQLSERVER中的ALLOCATION SCAN和RANGE SCAN

SQLSERVER中的ALLOCATION SCAN和RANGE SCAN

Jun 07, 2016 pm 05:38 PM
r scan sqlserver

SQLSERVER中的ALLOCATION SCAN和RANGE SCAN 写这篇文章的开始,我还不知道ALLOCATION SCAN的工作原理是怎样的,网上资料少得可怜 求助了园子里的某位大侠,他看了我的信息几天之后才回复我,不过他的回复里没有答案 这几天一直在苦思冥想,后来终于通过动手

SQLSERVER中的ALLOCATION SCAN和RANGE SCAN

写这篇文章的开始,我还不知道ALLOCATION SCAN的工作原理是怎样的,网上资料少得可怜

求助了园子里的某位大侠,他看了我的信息几天之后才回复我,不过他的回复里没有答案

这几天一直在苦思冥想,后来终于通过动手,验证出来了,知道ALLOCATION SCAN的工作原理是怎样的(结果中秋节过完就出差去了)

10月3日回到家马上开始动笔

在看下去之前请大家先看一下下面的文章

SQLSERVER聚集索引与非聚集索引的再次研究(上)
SQLSERVER聚集索引与非聚集索引的再次研究(下)
查看SQLSERVER内部数据页面的小插件Internals Viewer

SQLSERVER新建表的时候页面分配情况是怎样的?

存储引擎揭秘:基本结构之四——IAM页,IAM链和存储单元

SQL Server 2008存储结构之IAM结构

看这篇文章之前一定要非常清楚聚集索引页面/非聚集索引页面和IAM页面的作用

聚集索引页面:有指针,,有记录,可以准确定位到数据页面

非聚集索引页面:有指向堆中的指针,可以准确定位到数据页面

IAM页面:IAM页面只知道表中数据页面的分配情况,他不知道这些数据页面里都存储了哪些表中的记录

 

 

知识准备

我们回顾一下聚集索引的知识

一个数据页面只有一条记录

大家知道在聚集索引页面里,每一行都会指向一个数据页,如下图

SQL脚本

ct1(c1 INT, c2 VARCHAR (5000)); t1c1 ON ct1(c1); ; ; ) ct1 , 5000)) ct1 DBCCResult ( 30 PageFID NVARCHAR(200), 31 PagePID NVARCHAR(200), 32 IAMFID NVARCHAR(200), 33 IAMPID NVARCHAR(200), 34 ObjectID NVARCHAR(200), 35 IndexID NVARCHAR(200), 36 PartitionNumber NVARCHAR(200), 37 PartitionID NVARCHAR(200), 38 iam_chain_type NVARCHAR(200), 39 PageType NVARCHAR(200), 40 IndexLevel NVARCHAR(200), 41 NextPageFID NVARCHAR(200), 42 NextPagePID NVARCHAR(200), 43 PrevPageFID NVARCHAR(200), 44 PrevPagePID NVARCHAR(200) 45 ) .-- DBCCResult ) .TRACEON(3604,-1) PAGE(,1,175,3) 56 GO

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