SqlClient Akış DesteğiSqlClient Streaming Support

SQL Server ile bir uygulama (.NET Framework 4,5 ' de yeni) arasında akış desteği, sunucuda (belgeler, görüntüler ve medya dosyaları) yapılandırılmamış verileri destekler.Streaming support between SQL Server and an application (new in .NET Framework 4.5) supports unstructured data on the server (documents, images, and media files). Bir SQL Server veritabanı ikili büyük nesneleri (blob) saklayabilir, ancak Blobların alınması çok fazla bellek kullanabilir.A SQL Server database can store binary large objects (BLOBs), but retrieving BLOBS can use a lot of memory.

SQL Server akış desteği, verileri akışa almak zorunda kalmadan veri akışı yapan uygulamaların yazılmasını kolaylaştırır ve daha az bellek taşması özel durumu oluşmasına neden olur.Streaming support to and from SQL Server simplifies writing applications that stream data, without having to fully load the data into memory, resulting in fewer memory overflow exceptions.

Akış desteği, büyük Blobları göndermek, almak ve işlemek için, özellikle de iş nesnelerinin SQL Azure bağlanan senaryolarda, orta katman uygulamaların daha iyi ölçeklendirilmesine olanak tanır.Streaming support will also enable middle-tier applications to scale better, especially in scenarios where business objects connect to SQL Azure in order to send, retrieve, and manipulate large BLOBs.

Uyarı

Bir uygulama Context Connection bağlantı dizesi anahtar sözcüğünü de kullanıyorsa, zaman uyumsuz çağrılar desteklenmez.Asynchronous calls are not supported if an application also uses the Context Connection connection string keyword.

Akışı desteklemek için eklenen üyeler, sorgulardan verileri almak ve sorguları ve saklı yordamlara parametreleri geçirmek için kullanılır.The members added to support streaming are used to retrieve data from queries and to pass parameters to queries and stored procedures. Akış özelliği temel OLTP ve veri geçiş senaryolarına yöneliktir ve şirket içi ve şirket dışı veri geçişleri ortamları için geçerlidir.The streaming feature addresses basic OLTP and data migration scenarios and is applicable to on-premises and off-premises data migrations environments.

SQL Server akış desteğiStreaming Support from SQL Server

SQL Server akış desteği,, ve DbDataReader SqlDataReader Stream XmlReader nesneleri almak ve bunlara yanıt vermek için sınıflarında ve içindeki yeni işlevleri sunar TextReader .Streaming support from SQL Server introduces new functionality in the DbDataReader and in the SqlDataReader classes in order to get Stream, XmlReader, and TextReader objects and react to them. Bu sınıflar, sorgulardan verileri almak için kullanılır.These classes are used to retrieve data from queries. Sonuç olarak, SQL Server adresinden akış desteği OLTP senaryolarından ve şirket içi ve şirket dışı ortamlar için geçerlidir.As a result, Streaming support from SQL Server addresses OLTP scenarios and applies to on-premises and off-premises environments.

SqlDataReaderSQL Server 'den akış desteğini etkinleştirmek için aşağıdaki Üyeler eklenmiştir:The following members were added to SqlDataReader to enable streaming support from SQL Server:

  1. IsDBNullAsync

  2. SqlDataReader.GetFieldValue

  3. GetFieldValueAsync

  4. GetStream

  5. GetTextReader

  6. GetXmlReader

DbDataReaderSQL Server 'den akış desteğini etkinleştirmek için aşağıdaki Üyeler eklenmiştir:The following members were added to DbDataReader to enable streaming support from SQL Server:

  1. GetFieldValue

  2. GetStream

  3. GetTextReader

SQL Server için akış desteğiStreaming Support to SQL Server

SQL Server için akış desteği,, SqlParameter ve nesnelerini kabul etmek ve bunlara yanıt vermek için sınıfında yeni işlevsellik sunmaktadır XmlReader Stream TextReader .Streaming support to SQL Server introduces new functionality in the SqlParameter class so it can accept and react to XmlReader, Stream, and TextReader objects. SqlParameter , parametreleri sorgulara ve saklı yordamlara geçirmek için kullanılır.SqlParameter is used to pass parameters to queries and stored procedures.

Bir SqlCommand nesne veya çağrıyı elden atma Cancel tüm akış işlemlerini iptal etmelidir.Disposing a SqlCommand object or calling Cancel must cancel any streaming operation. Bir uygulama gönderirse CancellationToken iptali garanti edilmez.If an application sends CancellationToken, cancellation is not guaranteed.

Aşağıdaki SqlDbType türler öğesinin bir kabul edileceği Value Stream :The following SqlDbType types will accept a Value of Stream:

  • İkiliBinary

  • IkiliVarBinary

Aşağıdaki SqlDbType türler öğesinin bir kabul edileceği Value TextReader :The following SqlDbType types will accept a Value of TextReader:

  • CharChar

  • NCharNChar

  • NVarCharNVarChar

  • 'SiniXml

XML SqlDbType türü öğesinin bir kabul edileceği Value XmlReader .The XmlSqlDbType type will accept a Value of XmlReader.

SqlValue , ve türündeki değerleri kabul XmlReader edebilir TextReader Stream .SqlValue can accept values of type XmlReader, TextReader, and Stream.

XmlReader, TextReader Ve Stream nesnesi tarafından tanımlanan değere aktarılır Size .The XmlReader, TextReader, and Stream object will be transferred up to the value defined by the Size.

Örnek--SQL Server akışıSample -- Streaming from SQL Server

Örnek veritabanını oluşturmak için aşağıdaki Transact-SQL ' i kullanın:Use the following Transact-SQL to create the sample database:

CREATE DATABASE [Demo]
GO
USE [Demo]
GO
CREATE TABLE [Streams] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[textdata] NVARCHAR(MAX),
[bindata] VARBINARY(MAX),
[xmldata] XML)
GO
INSERT INTO [Streams] (textdata, bindata, xmldata) VALUES (N'This is a test', 0x48656C6C6F, N'<test>value</test>')
INSERT INTO [Streams] (textdata, bindata, xmldata) VALUES (N'Hello, World!', 0x54657374696E67, N'<test>value2</test>')
INSERT INTO [Streams] (textdata, bindata, xmldata) VALUES (N'Another row', 0x666F6F626172, N'<fff>bbb</fff><fff>bbc</fff>')
GO

Örnek, aşağıdakilerin nasıl yapılacağını göstermektedir:The sample shows how to do the following:

  • Büyük dosyaları almak için zaman uyumsuz bir yol sağlayarak bir kullanıcı arabirimi iş parçacığını engellemeyi önleyin.Avoid blocking a user-interface thread by providing an asynchronous way to retrieve large files.

  • SQL Server .NET Framework 4,5 ' de büyük bir metin dosyası aktarın.Transfer a large text file from SQL Server in .NET Framework 4.5.

  • Büyük bir XML dosyasını SQL Server .NET Framework 4,5 ' den aktarın.Transfer a large XML file from SQL Server in .NET Framework 4.5.

  • SQL Server verileri alın.Retrieve data from SQL Server.

  • Büyük dosyaları (Blobları) bir SQL Server veritabanından başka bir veritabanına aktarma belleği olmadan.Transfer large files (BLOBs) from one SQL Server database to another without running out of memory.

using System;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Threading.Tasks;
using System.Xml;

namespace StreamingFromServer {
   class Program {
      // Replace the connection string if needed, for instance to connect to SQL Express: @"Server=(local)\SQLEXPRESS;Database=Demo;Integrated Security=true"
      private const string connectionString = @"Server=(localdb)\V11.0;Database=Demo";

      static void Main(string[] args) {
         CopyBinaryValueToFile().Wait();
         PrintTextValues().Wait();
         PrintXmlValues().Wait();
         PrintXmlValuesViaNVarChar().Wait();

         Console.WriteLine("Done");
      }

      // Application retrieving a large BLOB from SQL Server in .NET Framework 4.5 using the new asynchronous capability
      private static async Task CopyBinaryValueToFile() {
         string filePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "binarydata.bin");

         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();
            using (SqlCommand command = new SqlCommand("SELECT [bindata] FROM [Streams] WHERE [id]=@id", connection)) {
               command.Parameters.AddWithValue("id", 1);

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire BLOB into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  if (await reader.ReadAsync()) {
                     if (!(await reader.IsDBNullAsync(0))) {
                        using (FileStream file = new FileStream(filePath, FileMode.Create, FileAccess.Write)) {
                           using (Stream data = reader.GetStream(0)) {

                              // Asynchronously copy the stream from the server to the file we just created
                              await data.CopyToAsync(file);
                           }
                        }
                     }
                  }
               }
            }
         }
      }

      // Application transferring a large Text File from SQL Server in .NET Framework 4.5
      private static async Task PrintTextValues() {
         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();
            using (SqlCommand command = new SqlCommand("SELECT [id], [textdata] FROM [Streams]", connection)) {

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire text document into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  while (await reader.ReadAsync()) {
                     Console.Write("{0}: ", reader.GetInt32(0));

                     if (await reader.IsDBNullAsync(1)) {
                        Console.Write("(NULL)");
                     }
                     else {
                        char[] buffer = new char[4096];
                        int charsRead = 0;
                        using (TextReader data = reader.GetTextReader(1)) {
                           do {
                              // Grab each chunk of text and write it to the console
                              // If you are writing to a TextWriter you should use WriteAsync or WriteLineAsync
                              charsRead = await data.ReadAsync(buffer, 0, buffer.Length);
                              Console.Write(buffer, 0, charsRead);
                           } while (charsRead > 0);
                        }
                     }

                     Console.WriteLine();
                  }
               }
            }
         }
      }

      // Application transferring a large Xml Document from SQL Server in .NET Framework 4.5
      private static async Task PrintXmlValues() {
         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();
            using (SqlCommand command = new SqlCommand("SELECT [id], [xmldata] FROM [Streams]", connection)) {

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire Xml Document into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  while (await reader.ReadAsync()) {
                     Console.WriteLine("{0}: ", reader.GetInt32(0));

                     if (await reader.IsDBNullAsync(1)) {
                        Console.WriteLine("\t(NULL)");
                     }
                     else {
                        using (XmlReader xmlReader = reader.GetXmlReader(1)) {
                           int depth = 1;
                           // NOTE: The XmlReader returned by GetXmlReader does NOT support async operations
                           // See the example below (PrintXmlValuesViaNVarChar) for how to get an XmlReader with asynchronous capabilities
                           while (xmlReader.Read()) {
                              switch (xmlReader.NodeType) {
                                 case XmlNodeType.Element:
                                    Console.WriteLine("{0}<{1}>", new string('\t', depth), xmlReader.Name);
                                    depth++;
                                    break;
                                 case XmlNodeType.Text:
                                    Console.WriteLine("{0}{1}", new string('\t', depth), xmlReader.Value);
                                    break;
                                 case XmlNodeType.EndElement:
                                    depth--;
                                    Console.WriteLine("{0}</{1}>", new string('\t', depth), xmlReader.Name);
                                    break;
                              }
                           }
                        }
                     }
                  }
               }
            }
         }
      }

      // Application transferring a large Xml Document from SQL Server in .NET Framework 4.5
      // This goes via NVarChar and TextReader to enable asynchronous reading
      private static async Task PrintXmlValuesViaNVarChar() {
         XmlReaderSettings xmlSettings = new XmlReaderSettings() {
            // Async must be explicitly enabled in the XmlReaderSettings otherwise the XmlReader will throw exceptions when async methods are called
            Async = true,
            // Since we will immediately wrap the TextReader we are creating in an XmlReader, we will permit the XmlReader to take care of closing\disposing it
            CloseInput = true,
            // If the Xml you are reading is not a valid document (as per <https://docs.microsoft.com/previous-versions/dotnet/netframework-4.0/6bts1x50(v=vs.100)>) you will need to set the conformance level to Fragment
            ConformanceLevel = ConformanceLevel.Fragment
         };

         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();

            // Cast the XML into NVarChar to enable GetTextReader - trying to use GetTextReader on an XML type will throw an exception
            using (SqlCommand command = new SqlCommand("SELECT [id], CAST([xmldata] AS NVARCHAR(MAX)) FROM [Streams]", connection)) {

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire Xml Document into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  while (await reader.ReadAsync()) {
                     Console.WriteLine("{0}:", reader.GetInt32(0));

                     if (await reader.IsDBNullAsync(1)) {
                        Console.WriteLine("\t(NULL)");
                     }
                     else {
                        // Grab the row as a TextReader, then create an XmlReader on top of it
                        // We are not keeping a reference to the TextReader since the XmlReader is created with the "CloseInput" setting (so it will close the TextReader when needed)
                        using (XmlReader xmlReader = XmlReader.Create(reader.GetTextReader(1), xmlSettings)) {
                           int depth = 1;
                           // The XmlReader above now supports asynchronous operations, so we can use ReadAsync here
                           while (await xmlReader.ReadAsync()) {
                              switch (xmlReader.NodeType) {
                                 case XmlNodeType.Element:
                                    Console.WriteLine("{0}<{1}>", new string('\t', depth), xmlReader.Name);
                                    depth++;
                                    break;
                                 case XmlNodeType.Text:
                                    // Depending on what your data looks like, you should either use Value or GetValueAsync
                                    // Value has less overhead (since it doesn't create a Task), but it may also block if additional data is required
                                    Console.WriteLine("{0}{1}", new string('\t', depth), await xmlReader.GetValueAsync());
                                    break;
                                 case XmlNodeType.EndElement:
                                    depth--;
                                    Console.WriteLine("{0}</{1}>", new string('\t', depth), xmlReader.Name);
                                    break;
                              }
                           }
                        }
                     }
                  }
               }
            }
         }
      }
   }
}

Örnek--SQL Server akışıSample -- Streaming to SQL Server

Örnek veritabanını oluşturmak için aşağıdaki Transact-SQL ' i kullanın:Use the following Transact-SQL to create the sample database:

CREATE DATABASE [Demo2]
GO
USE [Demo2]
GO
CREATE TABLE [BinaryStreams] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[bindata] VARBINARY(MAX))
GO
CREATE TABLE [TextStreams] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[textdata] NVARCHAR(MAX))
GO
CREATE TABLE [BinaryStreamsCopy] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[bindata] VARBINARY(MAX))
GO

Örnek, aşağıdakilerin nasıl yapılacağını göstermektedir:The sample shows how to do the following:

  • Büyük bir BLOBUN SQL Server .NET Framework 4,5 ' de aktarılıyor.Transferring a large BLOB to SQL Server in .NET Framework 4.5.

  • Büyük bir metin dosyasını .NET Framework 4,5 ' de SQL Server aktarma.Transferring a large text file to SQL Server in .NET Framework 4.5.

  • Büyük bir blobu aktarmak için yeni zaman uyumsuz özelliğini kullanma.Using the new asynchronous feature to transfer a large BLOB.

  • Büyük bir blobu aktarmak için yeni zaman uyumsuz özelliği ve await anahtar sözcüğünü kullanma.Using the new asynchronous feature and the await keyword to transfer a large BLOB.

  • Büyük bir BLOBUN aktarımı iptal ediliyor.Cancelling the transfer of a large BLOB.

  • Yeni zaman uyumsuz özelliği kullanarak bir SQL Server diğerine akış.Streaming from one SQL Server to another using the new asynchronous feature.

using System;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace StreamingToServer {
   class Program {
      // Replace the connection string if needed, for instance to connect to SQL Express: @"Server=(local)\SQLEXPRESS;Database=Demo2;Integrated Security=true"
      private const string connectionString = @"Server=(localdb)\V11.0;Database=Demo2";

      static void Main(string[] args) {
         CreateDemoFiles();

         StreamBLOBToServer().Wait();
         StreamTextToServer().Wait();

         // Create a CancellationTokenSource that will be cancelled after 100ms
         // Typically this token source will be cancelled by a user request (e.g. a Cancel button)
         CancellationTokenSource tokenSource = new CancellationTokenSource();
         tokenSource.CancelAfter(100);
         try {
            CancelBLOBStream(tokenSource.Token).Wait();
         }
         catch (AggregateException ex) {
            // Cancelling an async operation will throw an exception
            // Since we are using the Task's Wait method, this exception will be wrapped in an AggregateException
            // If you were using the 'await' keyword, the compiler would take care of unwrapping the AggregateException
            // Depending on when the cancellation occurs, you can either get an error from SQL Server or from .Net
            if ((ex.InnerException is SqlException) || (ex.InnerException is TaskCanceledException)) {
               // This is an expected exception
               Console.WriteLine("Got expected exception: {0}", ex.InnerException.Message);
            }
            else {
               // Did not expect this exception - re-throw it
               throw;
            }
         }

         Console.WriteLine("Done");
      }

      // This is used to generate the files which are used by the other sample methods
      private static void CreateDemoFiles() {
         Random rand = new Random();
         byte[] data = new byte[1024];
         rand.NextBytes(data);

         using (FileStream file = File.Open("binarydata.bin", FileMode.Create)) {
            file.Write(data, 0, data.Length);
         }

         using (StreamWriter writer = new StreamWriter(File.Open("textdata.txt", FileMode.Create))) {
            writer.Write(Convert.ToBase64String(data));
         }
      }

      // Application transferring a large BLOB to SQL Server in .NET Framework 4.5
      private static async Task StreamBLOBToServer() {
         using (SqlConnection conn = new SqlConnection(connectionString)) {
            await conn.OpenAsync();
            using (SqlCommand cmd = new SqlCommand("INSERT INTO [BinaryStreams] (bindata) VALUES (@bindata)", conn)) {
               using (FileStream file = File.Open("binarydata.bin", FileMode.Open)) {

                  // Add a parameter which uses the FileStream we just opened
                  // Size is set to -1 to indicate "MAX"
                  cmd.Parameters.Add("@bindata", SqlDbType.Binary, -1).Value = file;

                  // Send the data to the server asynchronously
                  await cmd.ExecuteNonQueryAsync();
               }
            }
         }
      }

      // Application transferring a large Text File to SQL Server in .NET Framework 4.5
      private static async Task StreamTextToServer() {
         using (SqlConnection conn = new SqlConnection(connectionString)) {
            await conn.OpenAsync();
            using (SqlCommand cmd = new SqlCommand("INSERT INTO [TextStreams] (textdata) VALUES (@textdata)", conn)) {
               using (StreamReader file = File.OpenText("textdata.txt")) {

                  // Add a parameter which uses the StreamReader we just opened
                  // Size is set to -1 to indicate "MAX"
                  cmd.Parameters.Add("@textdata", SqlDbType.NVarChar, -1).Value = file;

                  // Send the data to the server asynchronously
                  await cmd.ExecuteNonQueryAsync();
               }
            }
         }
      }

      // Cancelling the transfer of a large BLOB
      private static async Task CancelBLOBStream(CancellationToken cancellationToken) {
         using (SqlConnection conn = new SqlConnection(connectionString)) {
            // We can cancel not only sending the data to the server, but also opening the connection
            await conn.OpenAsync(cancellationToken);

            // Artificially delay the command by 100ms
            using (SqlCommand cmd = new SqlCommand("WAITFOR DELAY '00:00:00:100';INSERT INTO [BinaryStreams] (bindata) VALUES (@bindata)", conn)) {
               using (FileStream file = File.Open("binarydata.bin", FileMode.Open)) {

                  // Add a parameter which uses the FileStream we just opened
                  // Size is set to -1 to indicate "MAX"
                  cmd.Parameters.Add("@bindata", SqlDbType.Binary, -1).Value = file;

                  // Send the data to the server asynchronously
                  // Pass the cancellation token such that the command will be cancelled if needed
                  await cmd.ExecuteNonQueryAsync(cancellationToken);
               }
            }
         }
      }
   }
}

Örnek--bir SQL Server başka bir SQL Server akışSample -- Streaming From One SQL Server to Another SQL Server

Bu örnek, yük iptali desteğiyle, bir SQL Server büyük bir BLOBUN arasındaki zaman uyumsuz olarak nasıl akışa alınacağını gösterir.This sample demonstrates how to asynchronously stream a large BLOB from one SQL Server to another, with support for cancellation.

using System;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace StreamingFromServerToAnother {
   class Program {
      // Replace the connection string if needed, for instance to connect to SQL Express: @"Server=(local)\SQLEXPRESS;Database=Demo2;Integrated Security=true"
      private const string connectionString = @"Server=(localdb)\V11.0;Database=Demo2";

      static void Main(string[] args) {
         // For this example, we don't want to cancel
         // So we can pass in a "blank" cancellation token
         E2EStream(CancellationToken.None).Wait();

         Console.WriteLine("Done");
      }

      // Streaming from one SQL Server to Another One using the new Async.NET
      private static async Task E2EStream(CancellationToken cancellationToken) {
         using (SqlConnection readConn = new SqlConnection(connectionString)) {
            using (SqlConnection writeConn = new SqlConnection(connectionString)) {

               // Note that we are using the same cancellation token for calls to both connections\commands
               // Also we can start both the connection opening asynchronously, and then wait for both to complete
               Task openReadConn = readConn.OpenAsync(cancellationToken);
               Task openWriteConn = writeConn.OpenAsync(cancellationToken);
               await Task.WhenAll(openReadConn, openWriteConn);

               using (SqlCommand readCmd = new SqlCommand("SELECT [bindata] FROM [BinaryStreams]", readConn)) {
                  using (SqlCommand writeCmd = new SqlCommand("INSERT INTO [BinaryStreamsCopy] (bindata) VALUES (@bindata)", writeConn)) {

                     // Add an empty parameter to the write command which will be used for the streams we are copying
                     // Size is set to -1 to indicate "MAX"
                     SqlParameter streamParameter = writeCmd.Parameters.Add("@bindata", SqlDbType.Binary, -1);

                     // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
                     // Otherwise ReadAsync will buffer the entire BLOB into memory which can cause scalability issues or even OutOfMemoryExceptions
                     using (SqlDataReader reader = await readCmd.ExecuteReaderAsync(CommandBehavior.SequentialAccess, cancellationToken)) {
                        while (await reader.ReadAsync(cancellationToken)) {
                           // Grab a stream to the binary data in the source database
                           using (Stream dataStream = reader.GetStream(0)) {

                              // Set the parameter value to the stream source that was opened
                              streamParameter.Value = dataStream;

                              // Asynchronously send data from one database to another
                              await writeCmd.ExecuteNonQueryAsync(cancellationToken);
                           }
                        }
                     }
                  }
               }
            }
         }
      }
   }
}

Ayrıca bkz.See also