SQL Server表分区只支持range分区这一种类型,往往会被大家吐槽

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人家MySQL支持四种类型:RANGE分区、LIST分区、HASH分区、KEY分区
共同点是MySQL跟SQL Server也有分区对齐的问题,都是水平切分,大家都允许分区列存在NULL值
这次我们测试SQL Server表分区的分区列的NULL值,究竟NULL值是被存放在哪个区间,以前一直没有注意
测试脚本
- --1.创建文件组
 - ALTER DATABASE [sss]
 - ADD FILEGROUP [FG_TinyBlog_Id_01]
 - ALTER DATABASE [sss]
 - ADD FILEGROUP [FG_TinyBlog_Id_02]
 - ALTER DATABASE [sss]
 - ADD FILEGROUP [FG_TinyBlog_Id_03]
 - ALTER DATABASE [sss]
 - ADD FILEGROUP [FG_TinyBlog_Id_04]
 - ALTER DATABASE [sss]
 - ADD FILEGROUP [FG_TinyBlog_Id_05]
 - --2.创建文件
 - ALTER DATABASE [sss]
 - ADD FILE
 - (NAME = N'FG_TinyBlog_Id_01_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_01_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB )
 - TO FILEGROUP [FG_TinyBlog_Id_01];
 - ALTER DATABASE [sss]
 - ADD FILE
 - (NAME = N'FG_TinyBlog_Id_02_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_02_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB )
 - TO FILEGROUP [FG_TinyBlog_Id_02];
 - ALTER DATABASE [sss]
 - ADD FILE
 - (NAME = N'FG_TinyBlog_Id_03_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_03_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB )
 - TO FILEGROUP [FG_TinyBlog_Id_03];
 - ALTER DATABASE [sss]
 - ADD FILE
 - (NAME = N'FG_TinyBlog_Id_04_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_04_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB )
 - TO FILEGROUP [FG_TinyBlog_Id_04];
 - ALTER DATABASE [sss]
 - ADD FILE
 - (NAME = N'FG_TinyBlog_Id_05_data',FILENAME = N'E:\DataBase\sss\FG_TinyBlog_Id_05_data.ndf',SIZE = 96MB, FILEGROWTH = 24MB )
 - TO FILEGROUP [FG_TinyBlog_Id_05];
 - --3.创建分区函数
 - CREATE PARTITION FUNCTION
 - Fun_TinyBlog_Id(INT) AS
 - RANGE LEFT
 - FOR VALUES(-10,0,1,6)
 - --4.创建分区方案
 - CREATE PARTITION SCHEME
 - [Sch_TinyBlog_Id] AS
 - PARTITION [Fun_TinyBlog_Id]
 - TO([FG_TinyBlog_Id_01],[FG_TinyBlog_Id_02],[FG_TinyBlog_Id_03],[FG_TinyBlog_Id_04],[FG_TinyBlog_Id_05])
 
插入测试数据
- USE [sss]
 - CREATE TABLE TinyBlog(id INT NULL,NAME VARCHAR(100))
 - ON [Sch_TinyBlog_Id](id)
 - SELECT * FROM TinyBlog ORDER BY id
 - INSERT INTO [dbo].[TinyBlog]
 - ( [id], [NAME] )
 - VALUES ( NULL, -- id - int
 - '3232' -- NAME - varchar(100)
 - )
 - INSERT INTO [dbo].[TinyBlog]
 - ( [id], [NAME] )
 - VALUES ( -2, -- id - int
 - '-2' -- NAME - varchar(100)
 - )
 - INSERT INTO [dbo].[TinyBlog]
 - ( [id], [NAME] )
 - VALUES ( 66, -- id - int
 - '66' -- NAME - varchar(100)
 - )
 - INSERT INTO [dbo].[TinyBlog]
 - ( [id], [NAME] )
 - VALUES ( 0, -- id - int
 - '0' -- NAME - varchar(100)
 - )
 - INSERT INTO [dbo].[TinyBlog]
 - ( [id], [NAME] )
 - VALUES ( -30, -- id - int
 - '-30' -- NAME - varchar(100)
 - )
 
表数据如下
- SELECT * FROM TinyBlog ORDER BY id
 
分区分布
- --查看分区架构文件组分布
 - SELECT CONVERT(VARCHAR(MAX), ps.name) AS partition_scheme ,
 - p.partition_number ,
 - CONVERT(VARCHAR(MAX), ds2.name) AS filegroup ,
 - CONVERT(VARCHAR(MAX), ISNULL(v.value, ''), 120) AS range_boundary ,
 - STR(p.rows, 9) AS rows
 - FROM sys.indexes i
 - JOIN sys.partition_schemes ps ON i.data_space_id = ps.data_space_id
 - JOIN sys.destination_data_spaces dds ON ps.data_space_id = dds.partition_scheme_id
 - JOIN sys.data_spaces ds2 ON dds.data_space_id = ds2.data_space_id
 - JOIN sys.partitions p ON dds.destination_id = p.partition_number
 - AND p.object_id = i.object_id
 - AND p.index_id = i.index_id
 - JOIN sys.partition_functions pf ON ps.function_id = pf.function_id
 - LEFT JOIN sys.Partition_Range_values v ON pf.function_id = v.function_id
 - AND v.boundary_id = p.partition_number
 - - pf.boundary_value_on_right
 - WHERE i.object_id = OBJECT_ID('TinyBlog')
 - AND i.index_id IN ( 0, 1 )
 - ORDER BY p.partition_number
 - --分区区间
 - --SELECT * FROM sys.partition_range_values
 
分区情况
- --分区情况
 - SELECT c.* ,
 - b.[groupname] AS '分区方案对应的文件组名称' ,
 - d.name '当前分区函数对应的分区方案'
 - FROM sys.destination_data_spaces AS a
 - INNER JOIN sysfilegroups AS b ON a.[data_space_id] = b.[groupid]
 - INNER JOIN ( SELECT $PARTITION.Fun_TinyBlog_Id(id) AS 分区编号 ,
 - MIN(id) AS Min_value ,
 - MAX(id) AS Max_value ,
 - COUNT(id) AS 记录数
 - FROM [dbo].[TinyBlog]
 - GROUP BY $PARTITION.Fun_TinyBlog_Id(id)
 - ) AS c ON c.[分区编号] = a.[destination_id]
 - INNER JOIN sys.partition_schemes AS d ON a.[partition_scheme_id] = d.data_space_id
 - ORDER BY c.[分区编号]
 
第二个视图直接把NULL值忽略了
根据***个视图,我们画出一个总结图
分析一下
总结
结论其实很清晰,分区列不要允许NULL,如果允许列,那么我们交换分区归档数据的时候就会有麻烦了,因为无法判断分区列是NULL值的那些数据行是老数据还是新数据。
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