Trying to extract data form SQL using PS script - sql

Question

I have been trying to get a PS script to work in extracting files (pdf, word, etc.) from an SQL Server database. I came across the PowerShell script below. The script runs and populates the destination folder but all files are 0 bytes and during the script execution. It throws the error:
"Exporting Objects from FILESTREAM container: .docx
Exception calling "GetBytes" with "5" argument(s): "Invalid attempt to GetBytes on column 'extension'. The GetBytes function can only be used on columns of typ
e Text, NText, or Image.""
Can anyone point me in what am I doing wrong and how to fix this please? Much appreciated.
$Server = ".\xxxxxx";
$Database = "xxxxxx";
$Dest = "C:\DATA\";
$bufferSize = 8192;
$Sql = "
SELECT
[extension]
FROM [XXXXXXXX].[dbo].[XXXXXXdocuments]
";
$con = New-Object Data.SqlClient.SqlConnection;
$con.ConnectionString = "Data Source=$Server;" +
"Integrated Security=True;" +
"Initial Catalog=$Database";
$con.Open();
Write-Output ((Get-Date -format yyyy-MM-dd-HH:mm:ss) + ": Started ...");
$cmd = New-Object Data.SqlClient.SqlCommand $Sql, $con;
$cmd.CommandTimeout = 120
$rd = $cmd.ExecuteReader();
$out = [array]::CreateInstance('Byte', $bufferSize)
While ($rd.Read())
{
try
{
Write-Output ("Exporting Objects from FILESTREAM container: {0}" -f $rd.GetString(0));
$fs = New-Object System.IO.FileStream ($Dest + $rd.GetString(0)), Create, Write;
$bw = New-Object System.IO.BinaryWriter $fs;
$start = 0;
enter code here
$received = $rd.Getbytes(0, $start, $out, 0, $bufferSize - 1);
While ($received -gt 0)
{
$bw.Write($out, 0, $received);
$bw.Flush();
$start += $received;
$received = $rd.Getbytes(0, $start, $out, 0, $bufferSize - 1);
}
$bw.Close();
$fs.Close();
}
catch
{
Write-Output ($_.Exception.Message)
}
finally
{
$fs.Dispose();
}
}
$rd.Close();
$cmd.Dispose();
$con.Close();
Write-Output ("Finished");
Read-Host -Prompt "Press Enter to exit"

Answer 1

BinaryWriter is unnecessary. It's for writing primitive types to a Stream.
And there's no need to muck around with buffers; you can simply use SqlDataReader.GetStream(int).CopyTo(Stream), eg
$Server = "localhost";
$Database = "adventureworks2017";
$Dest = "C:\temp\";
$Sql = "
SELECT concat('photo', ProductPhotoID, '.jpg') name, LargePhoto from Production.ProductPhoto
";
$con = New-Object Data.SqlClient.SqlConnection;
$con.ConnectionString = "Data Source=$Server;Integrated Security=True;Initial Catalog=$Database;TrustServerCertificate=true";
$con.Open();
Write-Output ((Get-Date -format yyyy-MM-dd-HH:mm:ss) + ": Started ...");
$cmd = New-Object Data.SqlClient.SqlCommand $Sql, $con;
$cmd.CommandTimeout = 120
$rd = $cmd.ExecuteReader();
While ($rd.Read())
{
try
{
Write-Output ("Exporting: {0}" -f $rd.GetString(0));
$fs = New-Object System.IO.FileStream ($Dest + $rd.GetString(0)), Create, Write;
$rd.GetStream(1).CopyTo($fs)
$fs.Close()
}
catch
{
Write-Output ($_.Exception.Message)
}
finally
{
$fs.Dispose();
}
}
$rd.Close();
$cmd.Dispose();
$con.Close();
Write-Output ("Finished");