sql - 如何让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。

特别是一张表很大(22gb)，其中16.5gb是索引，剩下的5.5gb是数据。它包含略多于 12 000 000 行。

你能告诉我是否可以收缩索引？我已经尝试过重建、重组、重新创建聚簇索引、dbcc cleantable。我还知道 nvarchar 类型的大小是 varchar 的两倍，所以我将列类型更改为 varchar，但多亏了这一点，我只节省了大约 2 gb(1 gb 数据和 1 gb 索引)。

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

查看表定义

主键:

• 您有一个 char(32) 聚簇索引。这 32 个字节出现在每个 非聚集索引中

列:

• 为什么是 char(32)？ -> 可变字符(32)
• 为什么使用 nvarchar()？ -> 变量
• 为什么是日期时间？ -> 小日期时间
• 为什么是 ntext？ -> 可变字符(最大值)

索引:

• 您能否使用 INCLUDE 而不是使用键列

您的主要问题是聚集索引的选择不当。如果你不能解决这个问题，那么几乎所有其他事情都毫无意义:除非你删除数据......

当您更改为 varchar 时，您节省了 22GB 中的 2GB。这是 9%，这在没有其他优化的情况下是相当合理的。它还表明您不需要 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。最小为 3.7 GB (12 x 12,000,000 x 28)，但由于每页行数更多，因此会更多。而且它对客户端代码是透明的。

然后您开始检查索引使用...

但是，您应该考虑容量规划和数据增长规划。我在此处建议的更改将降低增长率 以及当前大小，但如果您还需要 5000 万行，则需要为此进行规划。例如，您可以压缩备份吗？