我正在执行数百行的简单插入,例如:
INSERT INTO Foo
SELECT * FROM Bar
该表有一些二级索引。禁用这些索引后,查询几乎立即运行。启用二级索引后,查询耗时数秒,子树成本较高。
问题是对于每个二级索引,数据库执行:
- 物理操作:Table spool
- 逻辑运算:Lazy spool
缓存位置:
- 目标表中的所有列(当它只需要它需要的值时)
- 多次值(而不是一次)
虽然了解为什么 SQL Server (2008 R2 SP2) 认为它需要这样做可能很有趣,但我真正需要的是一种方法,使在实时服务器中插入 100 行不需要花费太多时间六秒。
真正非常可怕的是,对于每个表假脱机,SQL Server 都会每次缓存每个列的值:
这只是燃烧逻辑IO。
- 如果没有这些有问题的索引更新,一两秒内即可完成 60,000 行的导入
- 使用这些索引,完成导入实际上需要几十分钟
重现步骤
当然,我的真实 AuditLog
表包含 4M 行。但是我们可以使用空的 AuditLog 表来重现完全相同的运算符,但子树成本很高:
CREATE TABLE [dbo].[AuditLog](
[AuditLogID] [int] IDENTITY(216,1) NOT NULL,
[ChangeDate] [datetime] NOT NULL CONSTRAINT [DF_AuditLog_ChangeDate] DEFAULT (getdate()),
[RowGUID] [uniqueidentifier] NOT NULL,
[ChangeType] [varchar](50) NOT NULL,
[TableName] [varchar](128) NOT NULL,
[FieldName] [varchar](128) NOT NULL,
[OldValue] [varchar](max) NULL,
[NewValue] [varchar](max) NULL,
[SystemUser] [varchar](128) NULL CONSTRAINT [DF_AuditLog_SystemUser] DEFAULT (suser_sname()),
[Username] [varchar](128) NOT NULL CONSTRAINT [DF_AuditLog_Username] DEFAULT (user_name()),
[Hostname] [varchar](50) NOT NULL CONSTRAINT [DF_AuditLog_Hostname] DEFAULT (host_name()),
[AppName] [varchar](128) NULL CONSTRAINT [DF_AuditLog_AppName] DEFAULT (app_name()),
[UserGUID] [uniqueidentifier] NULL,
[TagGUID] [uniqueidentifier] NULL,
[Tag] [varchar](max) NULL,
[timestamp] [timestamp] NOT NULL,
CONSTRAINT [PK_AuditLog] PRIMARY KEY CLUSTERED ([AuditLogID] ASC)
)
我们有痛苦的索引:
SET ANSI_PADDING OFF
GO
/****** Object: Index [IX_AuditLog_ChangeDate] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_ChangeDate] ON [dbo].[AuditLog]
(
[ChangeDate] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [IX_AuditLog_FieldName] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_FieldName] ON [dbo].[AuditLog]
(
[FieldName] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [IX_AuditLog_LastRowActionByTable] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_LastRowActionByTable] ON [dbo].[AuditLog]
(
[TableName] ASC,
[ChangeType] ASC,
[RowGUID] ASC,
[UserGUID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
/****** Object: Index [IX_AuditLog_RowGUID] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_RowGUID] ON [dbo].[AuditLog]
(
[RowGUID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [IX_AuditLog_RowInsertedByUserGUID] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_RowInsertedByUserGUID] ON [dbo].[AuditLog]
(
[ChangeType] ASC,
[RowGUID] ASC,
[UserGUID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
/****** Object: Index [IX_AuditLog_RowLastModifiedByUserGUID] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_RowLastModifiedByUserGUID] ON [dbo].[AuditLog]
(
[RowGUID] ASC,
[ChangeDate] ASC,
[UserGUID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
SET ANSI_PADDING ON
GO
/****** Object: Index [IX_AuditLog_TableName] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_TableName] ON [dbo].[AuditLog]
(
[TableName] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
/****** Object: Index [IX_AuditLog_TagGUID] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_TagGUID] ON [dbo].[AuditLog]
(
[TagGUID] ASC,
[RowGUID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
GO
/****** Object: Index [IX_AuditLog_UserGUID] Script Date: 11/17/2016 2:58:43 PM ******/
CREATE NONCLUSTERED INDEX [IX_AuditLog_UserGUID] ON [dbo].[AuditLog]
(
[ChangeDate] ASC,
[UserGUID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
然后我们创建插入内容:
INSERT INTO AuditLog(
RowGUID,
ChangeType,
UserGUID,
TableName,
FieldName,
TagGUID,
Tag)
SELECT
'E5E31EDD-7D39-47FD-BCFF-4B7044AC433D',
'INSERTED',
'4A2FDACD-0209-403B-ADBC-1B8A68E90350', --UserGUID
'Customers', --TableName
'', --FieldName
'7A74267D-64F9-44D7-A1D7-1490A66136BF', --TagGUID
'Contoso'
FROM (
--A dummy derived table that lets us select the above row 100 times
SELECT TOP 400 (a.Number * 256) + b.Number AS Number
FROM (
SELECT number FROM master..spt_values WHERE type = 'P' AND number <= 255) a (Number),
(SELECT number FROM master..spt_values WHERE type = 'P' AND number <= 255) b (Number)
) dt
您询问的等待时间?
| Wait Type | Wait Time (s) | Wait Count |
|----------------|---------------|------------|
| IO_COMPLETION | 4.55 s | 211 |
| WRITELOG | 0.79 s | 37 |
| PAGEIOLATCH_UP | 0.36 s | 1 |
| PAGELATCH_UP | 0.09 s | 2 |
| PAGEIOLATCH_EX | 0.07 s | 4 |
IO_COMPLETION
中 6 秒执行的 4.55 秒:
Occurs while waiting for I/O operations to complete. This wait type generally represents non-data page I/Os. Data page I/O completion waits appear as PAGEIOLATCH_* waits.
你说的是非冗余索引?
| Index Name | Columns | Index Entry Size |
|---------------------------------------|------------------------------------------|--------------------------|
| IX_AuditLog_ChangeDate | ChangeDate | 12 bytes per entry |
| IX_AuditLog_UserGUID | ChangeDate, UserGUID | 28 bytes per entry |
| IX_AuditLog_FieldName | FieldName | 4 bytes per entry (avg) |
| IX_AuditLog_TableName | TableName | 13 bytes per entry (avg) |
| IX_AuditLog_LastRowActionByTable | TableName, ChangeType, RowGUID, UserGUID | 52 bytes per entry (avg) |
| IX_AuditLog_RowGUID | RowGUID | 20 bytes per entry |
| IX_AuditLog_RowLastModifiedByUserGUID | RowGUID, ChangeDate, UserGUID | 44 bytes per entry |
| IX_AuditLog_RowInsertedByUserGUID | ChangeType, RowGUID, UserGUID | 43 bytes per entry (avg) |
| IX_AuditLog_TagGUID | TagGUID, RowGUID | 36 bytes per entry |
无排序警告
批处理的 SQL Server Profiler 结果
- 持续时间:7,401 毫秒
- 阅读量:233,597
- 写入:17,077
- CPU:1,141 毫秒
没有排序警告。也没有任何注意、位图警告、执行警告、哈希警告、缺少列统计信息、缺少连接谓词、排序警告、用户错误消息。
索引全部重建。所有统计数据均已更新。
最佳答案
您遇到重叠和冗余索引的问题。
关于sql-server - 索引插入期间的多个表假脱机(Eager 假脱机),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40664651/