Question

我的公司承诺在我们的Azure SQL数据库表中使用GUID作为主键（实际上比这更糟糕：我们使用VARCHAR（36）而不是UNIQUEIDENTIFIER）。因此，我们最终得到碎片索引。它们看起来像这样：

nodes.connectedEdges()

我通过创建新表“修复”了这个问题。这次，我为CLUSTERED INDEX使用了一个不可变的，不断增加的DATETIME2（例如CreateTime）列，并将VARCHAR（36）保持为PRIMARY KEY，但这次是NONCLUSTERED。像这样：

CREATE TABLE OldTable (
  Id VARCHAR(36) PRIMARY KEY CLUSTERED NOT NULL DEFAULT NEWID(),
  CreateTime DATETIME2 NOT NULL,
  ...
)

然后我使用INSERT INTO NewTable SELECT * FROM OldTable“将”行从旧表“复制”到新表。最后，我重命名表并删除旧表。生活似乎很好。

令我惊讶的是，几周之后，我发现NewTable有许多碎片索引，平均碎片率高达80％！甚至IX_NewTable_CreateTime也报告了18％的碎片。

INSERT INTO是否将索引分段？请问REBUILD指数能解决这个问题吗？

Answer 1

碎片取决于索引字段的插入/更新频率和索引页面的大小。

出于维护目的，您可以使用Azure自动化并创建一个定期脚本，以检查碎片索引并对其进行优化。

图库中有一本Runbook：

关于这一点，最好的事情是，只要你没有超过每月500分钟的运行时间，自动化是免费的，你的执行时间很长，而且你不需要支付：）

我对图库脚本进行了自定义改进，也随意使用它：

<#
.SYNOPSIS 
    Indexes tables in a database if they have a high fragmentation

.DESCRIPTION
    This runbook indexes all of the tables in a given database if the fragmentation is
    above a certain percentage. 
    It highlights how to break up calls into smaller chunks, 
    in this case each table in a database, and use checkpoints. 
    This allows the runbook job to resume for the next chunk of work even if the 
    fairshare feature of Azure Automation puts the job back into the queue every 30 minutes

.PARAMETER SqlServer
    Name of the SqlServer

.PARAMETER Database
    Name of the database

.PARAMETER SQLCredentialName
    Name of the Automation PowerShell credential setting from the Automation asset store. 
    This setting stores the username and password for the SQL Azure server

.PARAMETER FragPercentage
    Optional parameter for specifying over what percentage fragmentation to index database
    Default is 20 percent

 .PARAMETER RebuildOffline
    Optional parameter to rebuild indexes offline if online fails 
    Default is false

 .PARAMETER Table
    Optional parameter for specifying a specific table to index
    Default is all tables

.PARAMETER SqlServerPort
    Optional parameter for specifying the SQL port 
    Default is 1433

.EXAMPLE
    Update-SQLIndexRunbook -SqlServer "server.database.windows.net" -Database "Finance" -SQLCredentialName "FinanceCredentials"

.EXAMPLE
    Update-SQLIndexRunbook -SqlServer "server.database.windows.net" -Database "Finance" -SQLCredentialName "FinanceCredentials" -FragPercentage 30

.EXAMPLE
    Update-SQLIndexRunbook -SqlServer "server.database.windows.net" -Database "Finance" -SQLCredentialName "FinanceCredentials" -Table "Customers" -RebuildOffline $True

.NOTES
    AUTHOR: Matias Quaranta
    LASTEDIT: Jan 10th, 2015 
#>
workflow MyRunBook
{
    param(
        [parameter(Mandatory=$True)]
        [string] $SqlServer,

        [parameter(Mandatory=$True)]
        [string] $Database,

        [parameter(Mandatory=$True)]
        [string] $SQLCredentialName,

        [parameter(Mandatory=$False)]
        [int] $FragPercentage = 20,

        [parameter(Mandatory=$False)]
        [int] $SqlServerPort = 1433,

        [parameter(Mandatory=$False)]
        [boolean] $RebuildOffline = $False,

        [parameter(Mandatory=$False)]
        [string] $Table

    )

    # Get the stored username and password from the Automation credential
    $SqlCredential = Get-AutomationPSCredential -Name $SQLCredentialName
    if ($SqlCredential -eq $null)
    {
        throw "Could not retrieve '$SQLCredentialName' credential asset. Check that you created this first in the Automation service."
    }

    $SqlUsername = $SqlCredential.UserName 
    $SqlPass = $SqlCredential.GetNetworkCredential().Password

    InlineScript{

        # Define the connection to the SQL Database
        $Conn = New-Object System.Data.SqlClient.SqlConnection("Server=tcp:$using:SqlServer,$using:SqlServerPort;Database=$using:Database;User ID=$using:SqlUsername;Password=$using:SqlPass;Trusted_Connection=False;Encrypt=True;Connection Timeout=30;")

        # Open the SQL connection
        $Conn.Open()

        # SQL command to find tables and their average fragmentation
        $SQLCommandString = @"
        SELECT a.object_id, b.name, (select name from sys.tables t where t.object_id = b.object_id) as tablename, avg_fragmentation_in_percent
        FROM sys.dm_db_index_physical_stats (
               DB_ID(N'$Database')
             , OBJECT_ID(0)
             , NULL
             , NULL
             , NULL) AS a
        JOIN sys.indexes AS b 
        ON a.object_id = b.object_id AND a.index_id = b.index_id;
"@
        # Return the tables with their corresponding average fragmentation
        $Cmd=new-object system.Data.SqlClient.SqlCommand($SQLCommandString, $Conn)
        $Cmd.CommandTimeout=120

        # Execute the SQL command
        $FragmentedTable=New-Object system.Data.DataSet
        $Da=New-Object system.Data.SqlClient.SqlDataAdapter($Cmd)
        [void]$Da.fill($FragmentedTable)

 # Return the table names that have high fragmentation
        ForEach ($FragTable in $FragmentedTable.Tables[0])
        {

            If ($FragTable.avg_fragmentation_in_percent -ge $Using:FragPercentage)
            {
                Write-Verbose ("Index found : " +  $FragTable.name + " on table:" + $FragTable.tablename)

                $SQLCommandString = "EXEC('ALTER INDEX "+$FragTable.name+" ON "+$FragTable.tablename+" REBUILD')"

                $Cmd2=new-object system.Data.SqlClient.SqlCommand($SQLCommandString, $Conn)
                # Set the Timeout to be less than 30 minutes since the job will get queued if > 30
                # Setting to 25 minutes to be safe.
                $Cmd2.CommandTimeout=1500

                Try 
                {
                    $Ds=New-Object system.Data.DataSet
                    $Da=New-Object system.Data.SqlClient.SqlDataAdapter($Cmd2)
                    [void]$Da.fill($Ds)
                }
                Catch
                {
                    Write-Verbose ($FragTable.name +" on table "+$FragTable.tablename+" could NOT be indexed.")
                }
            }
        }

        $Conn.Close()
    }
    Write-Verbose "Finished Indexing"
}

为什么我的Azure SQL数据库索引仍然是碎片？

1 个答案: