I've found lots of information on how to select a BLOB as a stream using CommandBehavior.SequentialAccess.
I'd like to stream the BLOB on an insert too (to avoid caching the BLOB as a byte array in memory), and I can't find any examples. I've found some documentation mentioning a .WRITE (expression,@Offset, @Length) syntax in the UPDATE T-SQL statement which is compatible with VARBINARY(MAX). So, I'm thinking of writing a class which can take a Stream and chunk it into the database using successive UPDATE (.WRITE) statements. Is this the right way to do this, or is there a better way?
Links to UPDATE.WRITE:
http://msdn.microsoft.com/en-us/library/ms178158(SQL.100).aspx
http://msdn.microsoft.com/en-us/library/ms177523(v=SQL.100).aspx
Links to selecting BLOBs using CommandBehavior.SequentialAccess:
http://msdn.microsoft.com/en-us/library/87z0hy49.aspx
Memory effective way to read BLOB data in C#/SQL 2005
Getting binary data using SqlDataReader
How to make streams from BLOBs available in plain old C# objects when using SqlDataReader?
Streaming VARBINARY data from SQL Server in C#
Here's a POC of using the .Write syntax:
DDL:
create database BlobTest
go
use blobtest
go
create table Blob
(
Id bigint not null primary key identity(1,1),
Data varbinary(max) not null default(0x)
)
C#:
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Linq;
namespace ConsoleApplication1
{
class Program
{
static void Main()
{
string pathToBigFile = "C:\\bigfile.big";
int optimumBufferSizeForSql = 8040; //See https://stackoverflow.com/questions/5629991/how-can-i-generate-an-insert-script-for-a-table-with-a-varbinarymax-field
long newBlobId = InitialiseNewBlobInSqlServer();
using (Stream stream = new FileStream( pathToBigFile,
FileMode.Open,
FileAccess.Read,
FileShare.ReadWrite))
{
byte[] buffer = new byte[optimumBufferSizeForSql];
while(true)
{
int numberBytesRead = stream.Read(buffer, 0, optimumBufferSizeForSql);
if (numberBytesRead == 0)
{
//Done
break;
}
WriteBufferToSqlServer(
numberBytesRead == optimumBufferSizeForSql ? buffer : buffer.Take(numberBytesRead).ToArray(),
newBlobId);
}
}
}
static long InitialiseNewBlobInSqlServer()
{
using (SqlConnection conn = new SqlConnection("Data Source=localhost; Initial Catalog=BlobTest; Integrated Security=SSPI;"))
using (SqlCommand command = new SqlCommand())
{
command.Connection = conn;
command.CommandType = CommandType.Text;
command.CommandText = "Insert into blob (Data) values (0x); select convert(bigint,Scope_identity());";
conn.Open();
return (long) command.ExecuteScalar();
}
}
static void WriteBufferToSqlServer(byte[] data, long blobId)
{
using (SqlConnection conn = new SqlConnection("Data Source=localhost; Initial Catalog=BlobTest; Integrated Security=SSPI;"))
using (SqlCommand command = new SqlCommand())
{
command.Connection = conn;
command.CommandType = CommandType.Text;
command.Parameters.AddWithValue("@id", blobId);
command.Parameters.AddWithValue("@data", data);
command.CommandText = "Update Blob set Data.Write(@data, null, null) where Id = @id;";
conn.Open();
command.ExecuteNonQuery();
}
}
}
}
