使用PowerShell SQL Server DBATools的IDENTITY列阈值

In this article, we will review PowerShell SQL Server module DBATools to identify IDENTITY columns about to reach the threshold.

在本文中，我们将回顾PowerShell SQL Server模块DBATools，以识别即将达到阈值的IDENTITY列。

总览 (Overview)

In relational database engine, it is best practice to use an IDENTITY column to auto-generate column values. We define an identity column with a seed and step value. Once we insert a row into a SQL table, it automatically increases the value for that column. We can combine identity with a primary key to provide a unique identifier for a row. We can use integers and numeric data type for the identity column. We cannot insert value in the IDENTITY column explicitly.

在关系数据库引擎中，最佳实践是使用IDENTITY列自动生成列值。我们定义一个带有种子和步长值的标识列。一旦我们在SQL表中插入一行，它就会自动增加该列的值。我们可以将身份与主键结合起来，为行提供唯一的标识符。我们可以为标识列使用整数和数字数据类型。我们无法在IDENTITY列中明确插入值。

We can have the following data types for identity column along with the maximum values.

标识列可以具有以下数据类型以及最大值。

Data Type	Max Value	Storage
Tinyint	255	1 Byte
SmallInt	32,767	2 Bytes
Int	2³¹-1 (2,147,483,647)	4 Bytes
BigInt	2⁶³-1 (9,223,372,036,854,775,807)	8 bytes

数据类型	最大值	存储
Tinyint	255	1字节
SmallInt	32,767	2字节
整数	2 ³¹ -1（2,147,483,647）	4字节
大整数	2 ⁶³ -1（9,223,372,036,854,775,807）	8字节

We should use an appropriate data type to have better space utilization in the database. It is a important requirement while designing database tables.

我们应该使用适当的数据类型以更好地利用数据库中的空间。在设计数据库表时，这是一个重要的要求。

句法 (Syntax)

We need to define identity in a column with the following parameter.

我们需要使用以下参数在列中定义身份。

IDENTITY [(Seed, increment)]

身份[（种子，增量）]

Seed: Initial value of IDENTITY 种子：IDENTITY的初始值
Increment: Next value in an IDENTITY column is the last identity value plus seed. For example, in a table, the last IDENTITY value is 5, and we have defined seed 1, then the next value will be 6 增量：IDENTITY列中的下一个值是最后一个标识值加种子。例如，在一个表中，最后一个IDENTITY值是5，我们定义了种子1，那么下一个值将是6

Suppose you are doing an insert for SQL Table. You have defined identity on a column with data type Tinyint. You have reached the maximum limit for the identity column. If you still try to insert a row in that table, the query fails. We cannot insert any data in that situation. We either have to change the data type for that column or delete existing records and reseed IDENTITY.

假设您正在插入SQL表。您已经在数据类型为Tinyint的列上定义了身份。您已达到身份列的最大限制。如果您仍然尝试在该表中插入一行，则查询将失败。在这种情况下，我们无法插入任何数据。我们要么必须更改该列的数据类型，要么删除现有记录并重新设定IDENTITY。

Note: In this article, I am using DBATools using Azure Data Studio. You can also run these commands in Windows PowerShell.
注意： 在本文中，我将使用Azure Data Studio使用DBATools。 您也可以在Windows PowerShell中运行这些命令。

例 (Example)

Let us view the issue with an IDENTITY column using an example.

让我们使用示例通过IDENTITY列查看问题。

Use SQLSHACKDEMO
GO
CREATE TABLE [dbo].[DemoIdentityInsert] ([id] [tinyint] IDENTITY(1, 1) PRIMARY KEY NOT NULL,[Name] [nvarchar](20) NULL) ON [PRIMARY]
GO

Let us verify the current maximum value in the identity column

让我们在身份列中验证当前最大值
```
select max(id) as MaxIdentityValue from  DemoIdentityInsert
```

In the following screenshot, we can see we have reached to value 255.

在以下屏幕截图中，我们可以看到我们已达到255。

We can have a maximum of 255 values in the identity column for tinyint data type. Let us try to insert one more record in this table, and we get following Arithmetic overflow error. It is because it failed to insert value 256 in the identity column.

对于tinyint数据类型，在identity列中最多可以有255个值。让我们尝试在此表中再插入一条记录，然后得到以下算术溢出错误 。这是因为它无法在标识列中插入值256。

We can reproduce this error using int data type as follows. In the following query, we have set an initial value for the identity column as 2147483644. It will help us to reproduce the issue with a minimum number of rows.

我们可以使用int数据类型重现此错误，如下所示。在以下查询中，我们将身份列的初始值设置为2147483644。这将帮助我们以最少的行数重现该问题。

CREATE TABLE [dbo].[DemoIdentityInsert_1] ([id] [int] IDENTITY(2147483644 , 1) PRIMARY KEY NOT NULL,[Name] [nvarchar](20) NULL) ON [PRIMARY]
GO

We can have maximum 2147483644 values in identity column of the integer data type. Let us try to insert few records in this table. We get the similar message – Arithmetic overflow error converting IDENTITY to data type int.

在整数数据类型的标识列中，我们最多可以有2147483644个值。让我们尝试在此表中插入一些记录。我们得到类似的消息– 将IDENTITY转换为int数据类型的算术溢出错误。

If we are in a production environment, it might cause an outage where no users can insert data in an existing table. We should have a mechanism to identify that we are approaching near to maximum value in the identity column. We can take appropriate actions before it becomes an issue for us. We can write t-SQL code to know about identity values in our database. It requires you to be good in writing t-SQL along with knowledge about internal system tables.

如果我们在生产环境中，则可能会导致中断，导致没有用户可以在现有表中插入数据。我们应该有一种机制来标识我们正在接近标识列中的最大值。我们可以采取适当的措施，直到它成为我们的问题为止。我们可以编写t-SQL代码来了解数据库中的标识值。它要求您擅长编写t-SQL以及有关内部系统表的知识。

PowerShell SQL Server检查身份阈值 (PowerShell SQL Server to check IDENTITY threshold)

We can use PowerShell SQL Module DBATools for tracking identity values in the SQL Server database. You can follow my earlier article (see TOC at the bottom) to install it.

我们可以使用PowerShell SQL模块DBATools来跟踪SQL Server数据库中的标识值。您可以按照我之前的文章（请参阅底部的目录）进行安装。

Once installed, run the following code to get DBATools functions related to identity keyword.

安装后，运行以下代码以获取与identity关键字相关的DBATools函数。

>Get-Help *identity*

It gives following function in PowerShell SQL Server Module DBATools.

它在PowerShell SQL Server模块DBATools中提供以下功能。

Test-DbaIdentityUsage Test-DbaIdentity用法
Get-DbaDbIdentity Get-DbaDbIdentity
Set-DbaDBIdentity Set-DbaDBIdentity

Let us explore these DBATools(Test-DbaIdentityUsage and Get-DbaDbIdentity) functions in this article.

让我们探索本文中的这些DBATools（Test-DbaIdentityUsage和Get-DbaDbIdentity）函数。

Get-DbaDbIdentity (Get-DbaDbIdentity)

We can get information about current identity value in a table using Get-DbaDbIdentity function.

我们可以使用Get-DbaDbIdentity函数在表中获取有关当前身份值的信息。

First, let us get information about this PowerShell SQL Server module function Get-DbaDbIdentity.

首先，让我们获取有关此PowerShell SQL Server模块函数Get-DbaDbIdentity的信息。

>Get-Help Get-DbaDbIdentity

In the following example, we want to check IDENTITY value in DemoIdentityInsert table.

在下面的示例中，我们要检查DemoIdentityInsert表中的IDENTITY值。

>Get-DbaDbIdentity -SqlInstance Kashish\SQL2019CTP -Database SQLShackDemo -Table DemoIdentityInsert

It performs DBCC CHECKIDENT command with NORESEED option and returns the last value of identity column. By default, it gives output in the following format. You can use Format-Table –AutoSize or Out-GridView parameters to get output in a user-friendly way.

它使用NORESEED选项执行DBCC CHECKIDENT命令，并返回标识列的最后一个值。默认情况下，它以以下格式输出。您可以使用Format-Table –AutoSize或Out-GridView参数以用户友好的方式获取输出。

Get-DbaDbIdentity (Get-DbaDbIdentity)

We want to check IDENTITY seed usage as per the maximum value supported in a particular data type. We can use DBATools function Test-DbaIdentityUsage to retrieve useful information. It works on SQL Server 2008 and higher versions.

我们要根据特定数据类型支持的最大值来检查IDENTITY种子使用情况。我们可以使用DBATools函数Test-DbaIdentityUsage检索有用的信息。它适用于SQL Server 2008和更高版本。

In the following image, we can see the syntax and description of this. We can take help from the URL in the related links section as well.

在下图中，我们可以看到其语法和描述。我们也可以从相关链接部分的URL中获取帮助。

We have the following parameters in Test-DbaIdentityUsage.

我们在Test-DbaIdentityUsage中具有以下参数。

SqlInstance – We need to specify the instance name here. We can also specify multiple instances in this parameter SqlInstance –我们需要在此处指定实例名称。我们还可以在此参数中指定多个实例
SqlCredential – By default, DBATools command connects using Windows authentication. If we want to use SQL authentication, specify SQL login credentials here SqlCredential –默认情况下，DBATools命令使用Windows身份验证进行连接。如果要使用SQL身份验证，请在此处指定SQL登录凭据
Databases –We can also filter results for a particular database using this parameter. We cannot see this parameter in syntax because it is a dynamic parameter 数据库 –我们还可以使用此参数过滤特定数据库的结果。我们无法在语法中看到此参数，因为它是动态参数
Threshold – We can define a percentage threshold for the IDENTITY column 阈值 –我们可以为IDENTITY列定义百分比阈值
Excludesystem – usually, we do not create user objects in system databases. We can ignore checking identity for the system databases 排除系统 –通常，我们不在系统数据库中创建用户对象。我们可以忽略检查系统数据库的身份

Let us perform IDENTITY checks against all online databases in our SQL instance.

让我们对SQL实例中的所有在线数据库执行IDENTITY检查。

We might have a large number of databases and tables with IDENTITY columns. It returns output for each identity column in SQL instance. In the following screenshot, we can see a sample of it.

我们可能有大量带有IDENTITY列的数据库和表。它为SQL实例中的每个标识列返回输出。在下面的屏幕截图中，我们可以看到一个示例。

We can get a better representation of this information using Out-GridView format. Execute the following code, and it gives results in another window in a user-friendly way.

我们可以使用Out-GridView格式更好地表示此信息。执行以下代码，它以用户友好的方式在另一个窗口中提供结果。

We need to look at following columns in the Test-DbaIdentityUsage output.

我们需要查看Test-DbaIdentityUsage输出中的以下列。

LastValue: it shows the current maximum value in the IDENTITY column LastValue：在IDENTITY列中显示当前最大值
Percentused: it gives percentage usage of identity value against its data type maximum supported value 百分比 ：它给出了标识值相对于其数据类型最大支持值的使用百分比
Seedvalue: It gives an increment value for an IDENTITY column Seedvalue ：它为IDENTITY列提供增量值

Let us filter results using grid view filter. Click on Add Criteria and select a database from the drop-down list.

让我们使用网格视图过滤器过滤结果。单击添加条件，然后从下拉列表中选择一个数据库。

We can have multiple filters comparison filters to apply.

我们可以有多个过滤器比较过滤器来应用。

Equals 等于
Contains 包含
Does not contain 不含
Equals 等于
Does not equal 不相等
Ends with 以。。结束
Is empty 是空的
Is not empty 不为空

In the following screenshot, we set the filter for database SQLShackDemo.

在以下屏幕截图中，我们为数据库SQLShackDemo设置了过滤器。

In earlier demonstration, we used tables DemoIdentityInsert and DemoIdentityInsert_1 to show identity issues. We can see in Test-DbaIdentityUsage output; the identity column is 100 percent used. We get all IDENTITY columns in the specified database.

在较早的演示中，我们使用表DemoIdentityInsert和DemoIdentityInsert_1来显示身份问题。我们可以在Test-DbaIdentityUsage输出中看到；标识列已使用100％。我们获得指定数据库中的所有IDENTITY列。

We can perform these checks regularly and be sure of any identity threshold issues.

我们可以定期执行这些检查，并确保没有任何身份阈值问题。

Let us filter out the result for a particular database using Test-DbaIdentityUsage command.

让我们使用Test-DbaIdentityUsage命令过滤出特定数据库的结果。

>Test-DbaIdentityUsage -SqlInstance Kashish\SQL2019CTP -Database sqLShackDemo | Out-GridView

带有阈值的Get-DbaDbIdentity (Get-DbaDbIdentity with threshold)

We do not want output for all identity tables in our database. Suppose we want to set a warning threshold of 20%. If the percentage used for identity columns moves beyond 20% (80% of maximum data type value as possible identity values), we should get those entries in output. We need to specify -Threshold parameter like the following command.

我们不希望数据库中所有身份表的输出。假设我们要将警告阈值设置为20％。如果用于标识列的百分比超过20％（最大数据类型值的80％作为可能的标识值），我们应该在输出中获得这些条目。我们需要像以下命令一样指定-Threshold参数。

>Test-DbaIdentityUsage -SqlInstance Kashish\SQL2019CTP -Database sqLShackDemo -Threshold 20 | Out-GridView

In the following screenshot, we can see records for those tables exceeding a threshold value ( less than 80% possible identity values).

在下面的屏幕快照中，我们可以看到这些表的记录超过阈值（小于可能的标识值的80％）。

As of now, we performed a test for a single instance having multiple databases. Suppose we want to perform the test against multiple SQL instances. We need to specify multiple instance name separated by a comma.

到目前为止，我们对具有多个数据库的单个实例进行了测试。假设我们要对多个SQL实例执行测试。我们需要指定多个实例名称，用逗号分隔。

For example, let us Test-DbaIdentityUsage command for the following instances.

例如，让我们为以下实例使用Test-DbaIdentityUsage命令。

Kashish\SQL2019 Kashish \ SQL2019
Kashish\SQL2019CTP Kashish \ SQL2019CTP

In the following command, you can notice both instance names in SqlInstance parameter.

在以下命令中，您可以在SqlInstance参数中注意到两个实例名称。

>Test-DbaIdentityUsage -SqlInstance Kashish\SQL2019CTP,Kashish\SQL2019 -Threshold 20 | Out-GridView

We can see in the output identity columns for all databases in both instances exceeding a threshold value.

我们可以在两个实例的所有数据库的输出标识列中看到超过阈值的情况。

Let us rerun the command with a modified threshold of 70%. It shows tables having used identity values greater than 70% in both instances.

让我们以修改后的阈值70％重新运行该命令。它显示了在两种情况下使用的标识值都大于70％的表。

>Test-DbaIdentityUsage -SqlInstance Kashish\SQL2019CTP,Kashish\SQL2019 -Threshold 70 | Out-GridView

结论 (Conclusion)

We can proactively identify identity max out issues in SQL instances using PowerShell SQL Server module DBATools. You should implement regular checks on this to avoid any last minute surprise. We will cover more such validations in my further articles.

我们可以使用PowerShell SQL Server模块DBATools主动识别SQL实例中的最大身份问题。您应该对此进行定期检查，以免在最后一刻感到意外。我们将在后续文章中介绍更多此类验证。

目录 (Table of contents)

DBATools PowerShell Module for SQL Server

PowerShell SQL Server Validation Utility – DBAChecks

SQL Database Backups using PowerShell Module – DBATools

IDENTITY columns threshold using PowerShell SQL Server DBATools

DBATools PowerShell SQL Server Database Backups commands

SQL Restore Database using DBATools

Validate backups with SQL restore database operations using DBATools

Fix Orphan users in SQL Server using DBATools PowerShell

Creating a SQL Server Database using DBATools

Get SQL Database details using DBATools

Get-DbaHelpIndex command in DBATools

适用于SQL Server的DBATools PowerShell模块

PowerShell SQL Server验证实用程序– DBAChecks

使用PowerShell模块SQL数据库备份– DBATools

使用PowerShell SQL Server DBATools的IDENTITY列阈值

DBATools PowerShell SQL Server数据库备份命令

使用DBAToolsSQL Restore Database

使用DBATools通过SQL恢复数据库操作验证备份

使用DBATools PowerShell修复SQL Server中的孤立用户

使用DBATools创建SQL Server数据库

使用DBATools获取SQL数据库详细信息

DBATools中的Get-DbaHelpIndex命令

翻译自: https://www.sqlshack.com/identity-columns-threshold-using-powershell-sql-server-dbatools/