如何使SQL Server索引占用更少的空间？

Question

我有一个由某个应用程序创建的数据库.整个数据库超过50 GB,备份出现了一些问题,我的任务是让这个数据库尽可能小.

特别是一个表非常大(22 gb),其中16.5 gb是由索引获取的,其余5.5 gb是数据.它包含的行数不超过12 000 000.

你能告诉我是否可以缩小索引？我已经尝试过重建,重新组织,重新创建聚簇索引,dbcc清晰.我也知道nvarchar类型的大小比varchar大两倍,所以我将列类型更改为varchar,但是由于我节省了大约2 gb(数据上1 gb和索引上1 gb).

这是这个表的一个sql(fld0和fld1总是NULL):

CREATE TABLE [dbo].[DOC8](
 [ASSOCIATION] [nvarchar](64) NULL DEFAULT (NULL),
 [DOCID] [char](32) NOT NULL,
 [FLD0] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD1] [nvarchar](2048) NULL DEFAULT (NULL),
 [FLD10] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD2] [nvarchar](32) NULL DEFAULT (NULL),
 [FLD3] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD4] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD5] [datetime] NULL DEFAULT (NULL),
 [FLD6] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD7] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD8] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD9] [datetime] NULL DEFAULT (NULL),
 [PARENTID] [char](32) NULL DEFAULT (NULL),
 [POOLID] [char](32) NULL DEFAULT (NULL),
 [PROPERTIES] [ntext] NULL DEFAULT (NULL),
 [FLD11] [nvarchar](255) NULL DEFAULT (NULL),
 [FLD12] [nvarchar](255) NULL DEFAULT (NULL),
PRIMARY KEY CLUSTERED 
(
 [DOCID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_0] ON [dbo].[DOC8] 
(
 [ASSOCIATION] ASC,
 [PARENTID] ASC,
 [POOLID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_1] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD0] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_10] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD11] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_11] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD12] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_2] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD2] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_3] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD3] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_4] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD4] ASC,
 [FLD5] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_5] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD6] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_6] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD7] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_7] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD8] ASC,
 [FLD9] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_8] ON [dbo].[DOC8] 
(
 [POOLID] ASC,
 [FLD10] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO
CREATE NONCLUSTERED INDEX [DOC8_IDX_9] ON [dbo].[DOC8] 
(
 [PARENTID] ASC,
 [POOLID] ASC,
 [DOCID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO

Answer 1

看看你的表定义

首要的关键:

• 你有一个char(32)聚集索引.这32个字节出现在每个非聚集索引中

列:

• 为什么char(32)？ - > varchar(32)
• 为什么nvarchar()？ - > varchar
• 为什么选择datetime？ - > smalldatetime
• 为什么ntext？ - > varchar(max)

索引:

• 你可以使用INCLUDE而不是键列

您的主要问题是聚簇索引选择不当.如果你无法解决这个问题,那么其他一切都是毫无意义的:除非你删除数据......

当您更改为varchar时,您从22GB中节省了2GB.这是9%,这是相当合理的,没有其他优化.它还表明你不需要nvarchar ......

如果更改为int代理键,则每个非聚集索引每行可节省28个字节.这是最低3.7 GB(12 x 12,000,000 x 28),但由于每页有更多行,因此会更多.它对客户端代码透明.

然后你开始检查索引使用情况......

但是,您应该查看容量规划和数据增长计划.我建议这里的变化会降低增长速度,以及目前的规模,但如果你需要5000万行,那么你需要考虑这一点.例如,您可以压缩备份吗？

Answer 2

查找未使用的索引并将其删除.这也将减少驱动器为dui(删除,更新和插入)所做的写入量.请参阅Brent Ozar关于如何执行此操作的博客:http: //www.toadworld.com/platforms/sql-server/w/wiki/10062.find-indexes-not-in-use

基本上,如果你的读/写很低(<0.1),那么索引会伤害你,而不是它正在帮助并且可能还需要去.在删除索引之前,您需要仔细考虑.

您也可以从过滤的索引中受益.http://sqlfool.com/2009/04/filtered-indexes-what-you-need-to-know/