Question

我正在编写一个脚本来从SQL数据库中的BLOB中提取数据。提取过程很有效。我想在脚本中添加某种进度指示。我有一个SQL查询的总记录数，以及为每个导出的文件增加的增量计数器。增量计数器有效，但总记录数 - 我试图分配给全局变量 - 似乎没有保持其值。我不正确地宣布它吗？

## Export of "larger" Sql Server Blob to file            
## with GetBytes-Stream.         
# Configuration data     
$StartTime = Get-Date
$Server = "server";
$UserID = "user";
$Password = "password";
$Database = "db";
$Dest = "C:\Users\me\Desktop\Test\";
$bufferSize = 8192; 

# Counts total rows
$CountSql = "SELECT Count(extension) as countall from 
                (
                    SELECT  p.[people_id], right(pi.[file_name],4) as extension
                    FROM dbo.pictures as pi 
                    INNER JOIN dbo.people AS p ON p.person_picture = pi.pictures_id
                    where left([image_type], 5) = 'image'
                ) as countall"

# Selects Data
$Sql = "SELECT p.[people_id], pi.[image_file], right(pi.[file_name],4), ROW_NUMBER() OVER (ORDER BY people_id) as count
        FROM dbo.pictures as pi 
        INNER JOIN dbo.people AS p ON p.person_picture = pi.pictures_id
        where left([image_type], 5) = 'image'";    

# Open ADO.NET Connection            
$con = New-Object Data.SqlClient.SqlConnection;            
$con.ConnectionString = "Data Source=$Server;" +             
                        "Integrated Security=False;" + 
                        "User ID=$UserID;" +
                        "Password=$Password;" +           
                        "Initial Catalog=$Database";            
$con.Open();            

# New Command and Reader for total row count
$CountCmd = New-Object Data.SqlClient.SqlCommand $CountSql, $con;
$crd = $CountCmd.ExecuteReader();
While ($crd.Read())
{
    $crd.GetValue($global:1)
}
$crd.Close();

# New Command and Reader for rest of data     
$cmd = New-Object Data.SqlClient.SqlCommand $Sql, $con;            
$rd = $cmd.ExecuteReader();            

# Create a byte array for the stream.            
$out = [array]::CreateInstance('Byte', $bufferSize)            

# Looping through records
While ($rd.Read())            
{            
    $total = $global:1
    $counter = ($rd.GetValue(3));
    Write-Output ("Exporting $counter of $total`: {0}" -f $rd.GetGUID(0));

    # New BinaryWriter            
    $fs = New-Object System.IO.FileStream ($Dest + $rd.GetGUID(0) + $rd.GetString(2)), Create, Write;            
    $bw = New-Object System.IO.BinaryWriter $fs;            

    $start = 0;            
    # Read first byte stream            
    $received = $rd.GetBytes(1, $start, $out, 0, $bufferSize - 1);            
    While ($received -gt 0)            
    {            
       $bw.Write($out, 0, $received);            
       $bw.Flush();            
       $start += $received;            
       # Read next byte stream            
       $received = $rd.GetBytes(1, $start, $out, 0, $bufferSize - 1);            
    }            

    $bw.Close();            
    $fs.Close();            
}            

# Closing & Disposing all objects            
$fs.Dispose();            
$rd.Close();            
$cmd.Dispose();            
$con.Close();            
$EndTime = Get-Date
$TotalTime = $EndTime - $StartTime    
Write-Host ("Finished in {0:g}" -f $TotalTime)

输出

PS C:\Users\me> C:\Scripts\ExportImagesFromNTST.ps1
21380
Exporting 1 of : 3089b464-e667-4bf4-80b3-0002d582d4fa
Exporting 2 of : 04cf7738-ae19-4771-92b8-0003c5f27947
Exporting 3 of : 94485b5d-fe71-438d-a097-000ad185c915

等等。 21380应该是1美元，也应该是$ total。

Answer 1

我认为PetSerAl在这里击中了头。您创建了一个SqlCommand对象（$CountCmd），然后创建SqlDataReader（$crd），然后告诉$crd使用GetValue()接受一个整数作为参数的方法，以便它知道哪个列返回值，但是你引用一个名为“1”的全局变量，它永远不会被定义，所以你有效地传递$null到那个方法，所以它没有得到任何价值。我真的很惊讶它不会在那里给你带来错误。您可能希望只传递整数1作为该方法的参数，并将其分配给$Total循环中的While。老实说我在这里猜测，但从我看来，我认为它应该是：

$crd = $CountCmd.ExecuteReader();
While ($crd.Read())
{
    $Total = $crd.GetValue(0)
}
$crd.Close();

我很确定会分配第一列的值（对于那个sql命令应该只是1行，1列，对吗？只是总计数？），无论如何，为第一列分配第一列的值当前行到$Total。然后，您可以参考$Total，以便更新您的进度。

您是先生，如果您想跟踪进度，需要查看write-progress cmdlet，它非常适合您的脚本。

全局变量在循环外丢失值

1 个答案: