Objeto Transaction y operaciones de copia masiva
Las operaciones de copia masiva se pueden realizar como operaciones aisladas o como parte de una transacción en varios pasos. Esta última opción permite realizar más de una operación de copia masiva en la misma transacción, así como realizar otras operaciones de base de datos (como inserciones, actualizaciones y eliminaciones) mientras todavía se puede confirmar o revertir la transacción entera.
De forma predeterminada, una operación de copia masiva se realiza como una operación aislada. La operación de copia masiva tiene lugar sin transacciones y sin la oportunidad de revertirla. Si necesita revertir la copia masiva total o parcialmente cuando se produce un error, puede utilizar una transacción administrada por SqlBulkCopy, realizar la operación de copia masiva en una transacción existente o inscribirla en System.TransactionsTransaction.
Realización de una operación de copia masiva sin transacción
La aplicación de consola siguiente muestra lo que sucede cuando una operación de copia masiva sin transacciones detecta un error en medio de la operación.
En el ejemplo, las tablas de origen y de destino incluyen cada una una columna Identity denominada ProductID. En primer lugar, el código prepara la tabla de destino mediante la eliminación de todas las filas y luego inserta una sola fila cuyo ProductID se sabe que existe en la tabla de origen. De forma predeterminada, se genera un nuevo valor para la columna Identity en la tabla de destino para cada fila agregada. En este ejemplo, cuando se abre la conexión, se establece una opción que obliga al proceso de carga masiva a usar los valores Identity de la tabla de origen en su lugar.
La operación de copia masiva se ejecuta con la propiedad BatchSize establecida en 10. Cuando la operación encuentra la fila no válida, se produce una excepción. En este primer ejemplo, la operación de copia masiva es sin transacciones. Se confirman todos los lotes copiados hasta el punto del error; el lote que contiene la clave duplicada se revierte y la operación de copia masiva se detiene antes de procesar el resto de los lotes.
Nota:
Este ejemplo no se ejecuta a menos que haya creado las tablas de trabajo como se describe en Configuración de ejemplos de copia masiva. Este código se proporciona para mostrar la sintaxis para usar SqlBulkCopy. Si las tablas de origen y destino se encuentran en la misma instancia de SQL Server, es más fácil y rápido usar una instrucción INSERT … SELECT de Transact-SQL para copiar los datos.
var connectionString = GetConnectionString();
// Open a sourceConnection to the AdventureWorks database.
using (SqlConnection sourceConnection =
new(connectionString))
{
sourceConnection.Open();
// Delete all from the destination table.
SqlCommand commandDelete = new()
{
Connection = sourceConnection,
CommandText =
"DELETE FROM dbo.BulkCopyDemoMatchingColumns"
};
commandDelete.ExecuteNonQuery();
// Add a single row that will result in duplicate key
// when all rows from source are bulk copied.
// Note that this technique will only be successful in
// illustrating the point if a row with ProductID = 446
// exists in the AdventureWorks Production.Products table.
// If you have made changes to the data in this table, change
// the SQL statement in the code to add a ProductID that
// does exist in your version of the Production.Products
// table. Choose any ProductID in the middle of the table
// (not first or last row) to best illustrate the result.
SqlCommand commandInsert = new()
{
Connection = sourceConnection,
CommandText =
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns ON;" +
"INSERT INTO " + "dbo.BulkCopyDemoMatchingColumns " +
"([ProductID], [Name] ,[ProductNumber]) " +
"VALUES(446, 'Lock Nut 23','LN-3416');" +
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns OFF"
};
commandInsert.ExecuteNonQuery();
// Perform an initial count on the destination table.
SqlCommand commandRowCount = new(
"SELECT COUNT(*) FROM dbo.BulkCopyDemoMatchingColumns;",
sourceConnection);
long countStart = Convert.ToInt32(
commandRowCount.ExecuteScalar());
Console.WriteLine("Starting row count = {0}", countStart);
// Get data from the source table as a SqlDataReader.
SqlCommand commandSourceData = new(
"SELECT ProductID, Name, ProductNumber " +
"FROM Production.Product;", sourceConnection);
SqlDataReader reader = commandSourceData.ExecuteReader();
// Set up the bulk copy object using the KeepIdentity option.
using (SqlBulkCopy bulkCopy = new(
connectionString, SqlBulkCopyOptions.KeepIdentity))
{
bulkCopy.BatchSize = 10;
bulkCopy.DestinationTableName =
"dbo.BulkCopyDemoMatchingColumns";
// Write from the source to the destination.
// This should fail with a duplicate key error
// after some of the batches have been copied.
try
{
bulkCopy.WriteToServer(reader);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
reader.Close();
}
}
// Perform a final count on the destination
// table to see how many rows were added.
long countEnd = Convert.ToInt32(
commandRowCount.ExecuteScalar());
Console.WriteLine("Ending row count = {0}", countEnd);
Console.WriteLine("{0} rows were added.", countEnd - countStart);
Console.WriteLine("Press Enter to finish.");
Console.ReadLine();
}
Imports System.Data.SqlClient
Module Module1
Sub Main()
Dim connectionString As String = GetConnectionString()
' Open a sourceConnection to the AdventureWorks database.
Using sourceConnection As SqlConnection = _
New SqlConnection(connectionString)
sourceConnection.Open()
' Delete all from the destination table.
Dim commandDelete As New SqlCommand
commandDelete.Connection = sourceConnection
commandDelete.CommandText = _
"DELETE FROM dbo.BulkCopyDemoMatchingColumns"
commandDelete.ExecuteNonQuery()
' Add a single row that will result in duplicate key
' when all rows from source are bulk copied.
' Note that this technique will only be successful in
' illustrating the point if a row with ProductID = 446
' exists in the AdventureWorks Production.Products table.
' If you have made changes to the data in this table, change
' the SQL statement in the code to add a ProductID that
' does exist in your version of the Production.Products
' table. Choose any ProductID in the middle of the table
' (not first or last row) to best illustrate the result.
Dim commandInsert As New SqlCommand
commandInsert.Connection = sourceConnection
commandInsert.CommandText = _
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns ON;" & _
"INSERT INTO dbo.BulkCopyDemoMatchingColumns " & _
"([ProductID], [Name] ,[ProductNumber]) " & _
"VALUES(446, 'Lock Nut 23','LN-3416');" & _
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns OFF"
commandInsert.ExecuteNonQuery()
' Perform an initial count on the destination table.
Dim commandRowCount As New SqlCommand( _
"SELECT COUNT(*) FROM dbo.BulkCopyDemoMatchingColumns;", _
sourceConnection)
Dim countStart As Long = _
System.Convert.ToInt32(commandRowCount.ExecuteScalar())
Console.WriteLine("Starting row count = {0}", countStart)
' Get data from the source table as a SqlDataReader.
Dim commandSourceData As SqlCommand = New SqlCommand( _
"SELECT ProductID, Name, ProductNumber " & _
"FROM Production.Product;", sourceConnection)
Dim reader As SqlDataReader = _
commandSourceData.ExecuteReader()
' Set up the bulk copy object using the KeepIdentity option.
Using bulkCopy As SqlBulkCopy = New SqlBulkCopy(connectionString, _
SqlBulkCopyOptions.KeepIdentity)
bulkCopy.BatchSize = 10
bulkCopy.DestinationTableName = "dbo.BulkCopyDemoMatchingColumns"
' Write from the source to the destination.
' This should fail with a duplicate key error
' after some of the batches have already been copied.
Try
bulkCopy.WriteToServer(reader)
Catch ex As Exception
Console.WriteLine(ex.Message)
Finally
reader.Close()
End Try
End Using
' Perform a final count on the destination table
' to see how many rows were added.
Dim countEnd As Long = _
System.Convert.ToInt32(commandRowCount.ExecuteScalar())
Console.WriteLine("Ending row count = {0}", countEnd)
Console.WriteLine("{0} rows were added.", countEnd - countStart)
Console.WriteLine("Press Enter to finish.")
Console.ReadLine()
End Using
End Sub
Private Function GetConnectionString() As String
Throw New NotImplementedException()
End Function
End Module
Realización de una operación de copia masiva dedicada en una transacción
De forma predeterminada, una operación de copia masiva es su propia transacción. Si desea realizar una operación de copia masiva dedicada, cree una nueva instancia de SqlBulkCopy con una cadena de conexión o use un objeto SqlConnection existente sin una transacción activa. En cada escenario, la operación de copia masiva crea y confirma o revierte la transacción.
Puede especificar explícitamente la opción UseInternalTransaction en el constructor de la clase SqlBulkCopy para provocar de forma explícita una operación de copia masiva que se ejecute en su propia transacción, lo que da lugar a que cada lote de la operación de copia masiva se ejecute en una transacción independiente.
Nota
Dado que diferentes lotes se ejecutan en diferentes transacciones, si se produce un error durante la operación de copia masiva, se revertirán todas las filas del lote actual, pero las filas de los lotes anteriores permanecerán en la base de datos.
La aplicación de consola siguiente es similar al ejemplo anterior, con una excepción: en este caso, la operación de copia masiva administra sus propias transacciones. Se confirman todos los lotes copiados hasta el punto del error; el lote que contiene la clave duplicada se revierte y la operación de copia masiva se detiene antes de procesar el resto de los lotes.
Importante
Este ejemplo no se ejecuta a menos que haya creado las tablas de trabajo como se describe en Configuración de ejemplos de copia masiva. Este código se proporciona para mostrar la sintaxis para usar SqlBulkCopy. Si las tablas de origen y destino se encuentran en la misma instancia de SQL Server, es más fácil y rápido usar una instrucción INSERT … SELECT de Transact-SQL para copiar los datos.
var connectionString = GetConnectionString();
// Open a sourceConnection to the AdventureWorks database.
using (SqlConnection sourceConnection =
new(connectionString))
{
sourceConnection.Open();
// Delete all from the destination table.
SqlCommand commandDelete = new()
{
Connection = sourceConnection,
CommandText =
"DELETE FROM dbo.BulkCopyDemoMatchingColumns"
};
commandDelete.ExecuteNonQuery();
// Add a single row that will result in duplicate key
// when all rows from source are bulk copied.
// Note that this technique will only be successful in
// illustrating the point if a row with ProductID = 446
// exists in the AdventureWorks Production.Products table.
// If you have made changes to the data in this table, change
// the SQL statement in the code to add a ProductID that
// does exist in your version of the Production.Products
// table. Choose any ProductID in the middle of the table
// (not first or last row) to best illustrate the result.
SqlCommand commandInsert = new()
{
Connection = sourceConnection,
CommandText =
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns ON;" +
"INSERT INTO " + "dbo.BulkCopyDemoMatchingColumns " +
"([ProductID], [Name] ,[ProductNumber]) " +
"VALUES(446, 'Lock Nut 23','LN-3416');" +
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns OFF"
};
commandInsert.ExecuteNonQuery();
// Perform an initial count on the destination table.
SqlCommand commandRowCount = new(
"SELECT COUNT(*) FROM dbo.BulkCopyDemoMatchingColumns;",
sourceConnection);
long countStart = Convert.ToInt32(
commandRowCount.ExecuteScalar());
Console.WriteLine("Starting row count = {0}", countStart);
// Get data from the source table as a SqlDataReader.
SqlCommand commandSourceData = new(
"SELECT ProductID, Name, ProductNumber " +
"FROM Production.Product;", sourceConnection);
SqlDataReader reader = commandSourceData.ExecuteReader();
// Set up the bulk copy object.
// Note that when specifying the UseInternalTransaction
// option, you cannot also specify an external transaction.
// Therefore, you must use the SqlBulkCopy construct that
// requires a string for the connection, rather than an
// existing SqlConnection object.
using (SqlBulkCopy bulkCopy = new(
connectionString, SqlBulkCopyOptions.KeepIdentity |
SqlBulkCopyOptions.UseInternalTransaction))
{
bulkCopy.BatchSize = 10;
bulkCopy.DestinationTableName =
"dbo.BulkCopyDemoMatchingColumns";
// Write from the source to the destination.
// This should fail with a duplicate key error
// after some of the batches have been copied.
try
{
bulkCopy.WriteToServer(reader);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
reader.Close();
}
}
// Perform a final count on the destination
// table to see how many rows were added.
long countEnd = Convert.ToInt32(
commandRowCount.ExecuteScalar());
Console.WriteLine("Ending row count = {0}", countEnd);
Console.WriteLine("{0} rows were added.", countEnd - countStart);
Console.WriteLine("Press Enter to finish.");
Console.ReadLine();
}
Imports System.Data.SqlClient
Module Module1
Sub Main()
Dim connectionString As String = GetConnectionString()
' Open a sourceConnection to the AdventureWorks database.
Using sourceConnection As SqlConnection = _
New SqlConnection(connectionString)
sourceConnection.Open()
' Delete all from the destination table.
Dim commandDelete As New SqlCommand
commandDelete.Connection = sourceConnection
commandDelete.CommandText = _
"DELETE FROM dbo.BulkCopyDemoMatchingColumns"
commandDelete.ExecuteNonQuery()
' Add a single row that will result in duplicate key
' when all rows from source are bulk copied.
' Note that this technique will only be successful in
' illustrating the point if a row with ProductID = 446
' exists in the AdventureWorks Production.Products table.
' If you have made changes to the data in this table, change
' the SQL statement in the code to add a ProductID that
' does exist in your version of the Production.Products
' table. Choose any ProductID in the middle of the table
' (not first or last row) to best illustrate the result.
Dim commandInsert As New SqlCommand
commandInsert.Connection = sourceConnection
commandInsert.CommandText = _
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns ON;" & _
"INSERT INTO dbo.BulkCopyDemoMatchingColumns " & _
"([ProductID], [Name] ,[ProductNumber]) " & _
"VALUES(446, 'Lock Nut 23','LN-3416');" & _
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns OFF"
commandInsert.ExecuteNonQuery()
' Perform an initial count on the destination table.
Dim commandRowCount As New SqlCommand( _
"SELECT COUNT(*) FROM dbo.BulkCopyDemoMatchingColumns;", _
sourceConnection)
Dim countStart As Long = _
System.Convert.ToInt32(commandRowCount.ExecuteScalar())
Console.WriteLine("Starting row count = {0}", countStart)
' Get data from the source table as a SqlDataReader.
Dim commandSourceData As SqlCommand = New SqlCommand( _
"SELECT ProductID, Name, ProductNumber " & _
"FROM Production.Product;", sourceConnection)
Dim reader As SqlDataReader = _
commandSourceData.ExecuteReader()
' Set up the bulk copy object.
' Note that when specifying the UseInternalTransaction option,
' you cannot also specify an external transaction. Therefore,
' you must use the SqlBulkCopy construct that requires a string
' for the connection, rather than an existing SqlConnection object.
Using bulkCopy As SqlBulkCopy = New SqlBulkCopy(connectionString, _
SqlBulkCopyOptions.UseInternalTransaction Or _
SqlBulkCopyOptions.KeepIdentity)
bulkCopy.BatchSize = 10
bulkCopy.DestinationTableName = "dbo.BulkCopyDemoMatchingColumns"
' Write from the source to the destination.
' This should fail with a duplicate key error
' after some of the batches have already been copied.
Try
bulkCopy.WriteToServer(reader)
Catch ex As Exception
Console.WriteLine(ex.Message)
Finally
reader.Close()
End Try
End Using
' Perform a final count on the destination table
' to see how many rows were added.
Dim countEnd As Long = _
System.Convert.ToInt32(commandRowCount.ExecuteScalar())
Console.WriteLine("Ending row count = {0}", countEnd)
Console.WriteLine("{0} rows were added.", countEnd - countStart)
Console.WriteLine("Press Enter to finish.")
Console.ReadLine()
End Using
End Sub
Private Function GetConnectionString() As String
Throw New NotImplementedException()
End Function
End Module
Uso de transacciones existentes
Puede especificar un objeto SqlTransaction existente como un parámetro en un constructor de SqlBulkCopy. En esta situación, la operación de copia masiva se realiza en una transacción existente y el estado de la transacción no sufre ningún cambio (es decir, no se confirma ni se anula). Esto permite que una aplicación incluya la operación de copia masiva en una transacción con otras operaciones de base de datos. Sin embargo, si no se especifica un objeto SqlTransaction y se pasa una referencia nula, y la conexión tiene una transacción activa, se produce una excepción.
Si se produce un error y necesita revertir toda la operación de copia masiva, o si la copia masiva debe ejecutarse como parte de un proceso más grande que se pueda revertir, puede proporcionar un objeto SqlTransaction al constructor de SqlBulkCopy.
La siguiente aplicación de consola es similar al primer ejemplo (sin transacciones), con una excepción: en este ejemplo, la operación de copia masiva se incluye en una transacción externa más grande. Cuando se produce la infracción de la clave principal, toda la transacción se revierte y no se agrega ninguna fila a la tabla de destino.
Importante
Este ejemplo no se ejecuta a menos que haya creado las tablas de trabajo como se describe en Configuración de ejemplos de copia masiva. Este código se proporciona para mostrar la sintaxis para usar SqlBulkCopy. Si las tablas de origen y destino se encuentran en la misma instancia de SQL Server, es más fácil y rápido usar una instrucción INSERT … SELECT de Transact-SQL para copiar los datos.
var connectionString = GetConnectionString();
// Open a sourceConnection to the AdventureWorks database.
using (SqlConnection sourceConnection =
new(connectionString))
{
sourceConnection.Open();
// Delete all from the destination table.
SqlCommand commandDelete = new()
{
Connection = sourceConnection,
CommandText =
"DELETE FROM dbo.BulkCopyDemoMatchingColumns"
};
commandDelete.ExecuteNonQuery();
// Add a single row that will result in duplicate key
// when all rows from source are bulk copied.
// Note that this technique will only be successful in
// illustrating the point if a row with ProductID = 446
// exists in the AdventureWorks Production.Products table.
// If you have made changes to the data in this table, change
// the SQL statement in the code to add a ProductID that
// does exist in your version of the Production.Products
// table. Choose any ProductID in the middle of the table
// (not first or last row) to best illustrate the result.
SqlCommand commandInsert = new()
{
Connection = sourceConnection,
CommandText =
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns ON;" +
"INSERT INTO " + "dbo.BulkCopyDemoMatchingColumns " +
"([ProductID], [Name] ,[ProductNumber]) " +
"VALUES(446, 'Lock Nut 23','LN-3416');" +
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns OFF"
};
commandInsert.ExecuteNonQuery();
// Perform an initial count on the destination table.
SqlCommand commandRowCount = new(
"SELECT COUNT(*) FROM dbo.BulkCopyDemoMatchingColumns;",
sourceConnection);
long countStart = Convert.ToInt32(
commandRowCount.ExecuteScalar());
Console.WriteLine("Starting row count = {0}", countStart);
// Get data from the source table as a SqlDataReader.
SqlCommand commandSourceData = new(
"SELECT ProductID, Name, ProductNumber " +
"FROM Production.Product;", sourceConnection);
SqlDataReader reader = commandSourceData.ExecuteReader();
//Set up the bulk copy object inside the transaction.
using (SqlConnection destinationConnection =
new(connectionString))
{
destinationConnection.Open();
using (SqlTransaction transaction =
destinationConnection.BeginTransaction())
{
using (SqlBulkCopy bulkCopy = new(
destinationConnection, SqlBulkCopyOptions.KeepIdentity,
transaction))
{
bulkCopy.BatchSize = 10;
bulkCopy.DestinationTableName =
"dbo.BulkCopyDemoMatchingColumns";
// Write from the source to the destination.
// This should fail with a duplicate key error.
try
{
bulkCopy.WriteToServer(reader);
transaction.Commit();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
transaction.Rollback();
}
finally
{
reader.Close();
}
}
}
}
// Perform a final count on the destination
// table to see how many rows were added.
long countEnd = Convert.ToInt32(
commandRowCount.ExecuteScalar());
Console.WriteLine("Ending row count = {0}", countEnd);
Console.WriteLine("{0} rows were added.", countEnd - countStart);
Console.WriteLine("Press Enter to finish.");
Console.ReadLine();
}
Imports System.Data.SqlClient
Module Module1
Sub Main()
Dim connectionString As String = GetConnectionString()
' Open a sourceConnection to the AdventureWorks database.
Using sourceConnection As SqlConnection = _
New SqlConnection(connectionString)
sourceConnection.Open()
' Delete all from the destination table.
Dim commandDelete As New SqlCommand
commandDelete.Connection = sourceConnection
commandDelete.CommandText = _
"DELETE FROM dbo.BulkCopyDemoMatchingColumns"
commandDelete.ExecuteNonQuery()
' Add a single row that will result in duplicate key
' when all rows from source are bulk copied.
' Note that this technique will only be successful in
' illustrating the point if a row with ProductID = 446
' exists in the AdventureWorks Production.Products table.
' If you have made changes to the data in this table, change
' the SQL statement in the code to add a ProductID that
' does exist in your version of the Production.Products
' table. Choose any ProductID in the middle of the table
' (not first or last row) to best illustrate the result.
Dim commandInsert As New SqlCommand
commandInsert.Connection = sourceConnection
commandInsert.CommandText = _
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns ON;" & _
"INSERT INTO dbo.BulkCopyDemoMatchingColumns " & _
"([ProductID], [Name] ,[ProductNumber]) " & _
"VALUES(446, 'Lock Nut 23','LN-3416');" & _
"SET IDENTITY_INSERT dbo.BulkCopyDemoMatchingColumns OFF"
commandInsert.ExecuteNonQuery()
' Perform an initial count on the destination table.
Dim commandRowCount As New SqlCommand( _
"SELECT COUNT(*) FROM dbo.BulkCopyDemoMatchingColumns;", _
sourceConnection)
Dim countStart As Long = _
System.Convert.ToInt32(commandRowCount.ExecuteScalar())
Console.WriteLine("Starting row count = {0}", countStart)
' Get data from the source table as a SqlDataReader.
Dim commandSourceData As SqlCommand = New SqlCommand( _
"SELECT ProductID, Name, ProductNumber " & _
"FROM Production.Product;", sourceConnection)
Dim reader As SqlDataReader = _
commandSourceData.ExecuteReader()
' Set up the bulk copy object inside the transaction.
Using destinationConnection As SqlConnection = _
New SqlConnection(connectionString)
destinationConnection.Open()
Using transaction As SqlTransaction = _
destinationConnection.BeginTransaction()
Using bulkCopy As SqlBulkCopy = New _
SqlBulkCopy(destinationConnection, _
SqlBulkCopyOptions.KeepIdentity, transaction)
bulkCopy.BatchSize = 10
bulkCopy.DestinationTableName = _
"dbo.BulkCopyDemoMatchingColumns"
' Write from the source to the destination.
' This should fail with a duplicate key error.
Try
bulkCopy.WriteToServer(reader)
transaction.Commit()
Catch ex As Exception
Console.WriteLine(ex.Message)
transaction.Rollback()
Finally
reader.Close()
End Try
End Using
End Using
End Using
' Perform a final count on the destination table
' to see how many rows were added.
Dim countEnd As Long = _
System.Convert.ToInt32(commandRowCount.ExecuteScalar())
Console.WriteLine("Ending row count = {0}", countEnd)
Console.WriteLine("{0} rows were added.", countEnd - countStart)
Console.WriteLine("Press Enter to finish.")
Console.ReadLine()
End Using
End Sub
Private Function GetConnectionString() As String
Throw New NotImplementedException()
End Function
End Module