Whats wrong with this PowerShell script? - sql

Question

I am trying to export sql filestream data using powershell script and it exports only upto 8kb and it fails to export if the file is more than 8kb. But it creates the file partially. I dont know what is missing.
$Server = "(local)"; # SQL Server Instance.
$Database = "AdventureWorks";
$Dest = "D:\Export\"; # Path to export to.
$bufferSize = 8192; # Stream buffer size in bytes.
$con = New-Object Data.SqlClient.SqlConnection;
$con.ConnectionString = "Data Source=$Server;" +
"Integrated Security=True;" +
"Initial Catalog=$Database";
$con.Open();
[System.Data.SqlClient.SqlTransaction]$tran = $con.BeginTransaction("fs");
$Sql = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()";
$ctx = [array]::CreateInstance('Byte', 16);
$cmdct = New-Object Data.SqlClient.SqlCommand($Sql, $con, $tran);
$ctx = $cmdct.ExecuteScalar();
$cmdct.Dispose();
$Sql = "SELECT [FileName]
,[FileStreamData].PathName()
FROM dbo.FileStreamStorage ";
$out = [array]::CreateInstance('Byte', $bufferSize);
$cmd = New-Object Data.SqlClient.SqlCommand($Sql, $con, $tran);
$rd = $cmd.ExecuteReader();
While ($rd.Read())
{
Write-Output ("Exporting: {0}" -f $rd.GetString(0));
$fs = New-Object System.IO.FileStream ($Dest + $rd.GetString(0)), Create, Write;
$bw = New-Object System.IO.BinaryWriter($fs);
$sfs = New-Object System.Data.SqlTypes.SqlFileStream $rd.GetString(1), $ctx, Read, None, 0;
$start = 0;
While (1 -eq 1)
{
$received = $sfs.Read($out, $start, $bufferSize - 1);
$bw.Write($out, 0, $received);
$bw.Flush();
$start += $received;
If ($received -lt $bufferSize)
{ break; }
}
$bw.Close();
$fs.Close();
$sfs.Close();
}
$fs.Dispose();
$sfs.Dispose();
$rd.Close();
$rd.Dispose();
$tran.Commit();
$cmd.Dispose();
$tran.Dispose();
$con.Close();
$con.Dispose();
Write-Output ("Finished");
Any help will be really appreciated.

Answer 1

I think you are reading 8191 bytes, which means that $received will be 8191 if theres more data than this.
$received = $sfs.Read($out, $start, **$bufferSize - 1**);
Then you compare $received (8191) to $bufferSize (8192)
If ($received -lt $bufferSize)

Answer 2

I've done some work with filestreams and Powershell and I would agree with other comments--It appears there's an issue in how you are getting the length. Here's some code from my blog http://sev17.com/2010/05/11/t-sql-tuesday-006-blobs-filestream-and-powershell/ which demonstrates retrieving filestream data to a an image file:
$server = "Z002sql2k8"
$database = "AdventureWorks2008"
$query = "SELECT TOP(10) Document.PathName(), GET_FILESTREAM_TRANSACTION_CONTEXT(), Title + FileExtension AS FileName FROM Production.Document WHERE FileExtension = '.doc'"
$dirPath = "C:Usersu00"
$connection=new-object System.Data.SqlClient.SQLConnection
$connection.ConnectionString="Server={0};Database={1};Integrated Security=True" -f $server,$database
$connection.Open()
$command=new-object system.Data.SqlClient.SqlCommand("",$connection)
$command.CommandTimeout=120
$tran = $connection.BeginTransaction([System.Data.IsolationLevel]'ReadCommitted')
$command.Transaction = $tran
$command.CommandText = $query
$reader = $command.ExecuteReader()
while ($reader.Read())
{
$path = $reader.GetString(0)
[byte[]]$transactionContext = $reader.GetSqlBytes(1).Buffer
$filepath = "$dirPath{0}" -f $reader.GetValue(2)
$fileStream = new-object System.Data.SqlTypes.SqlFileStream($path,[byte[]]$reader.GetValue(1), [System.IO.FileAccess]'Read', [System.IO.FileOptions]'SequentialScan', 0)
$buffer = new-object byte[] $fileStream.Length
$fileStream.Read($buffer,0,$fileStream.Length)
$fileStream.Close()
[System.IO.File]::WriteAllBytes($filepath,$buffer)
}
$reader.Close()
$tran.Commit()
$connection.Close()