如何在插入时将BLOB流式传输到VARBINARY（MAX）

Question

我发现了很多关于如何使用CommandBehavior.SequentialAccess将BLOB选择为流的信息。

我想插入BLOB（避免将BLOB缓存为内存中的字节数组），我找不到任何示例。我在UPDATE T-SQL语句中发现了一些提及.WRITE (expression,@Offset, @Length)语法的文档，该语句与VARBINARY(MAX)兼容。所以，我正在考虑编写一个可以采用Stream的类，并使用连续的UPDATE（.WRITE）语句将它组合到数据库中。这是做这件事的正确方法，还是有更好的办法？

链接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

链接到选择的BLOB使用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#

下面是一个使用.WRITE语法的POC：

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(); 
      } 
     } 
    } 
} 

Answer 1

您应该使用SQL Server的RBS接口来处理blob。