Using NHibernate transaction in SqlBulkCopy

Question

I'm storing some data using NHibernate, and I need to insert huge amount of data as a part of this action - ie in the same transaction. Code looks like this:

using (ISession session = NHibernateHelper.OpenSession())
using (ITransaction transaction = session.BeginTransaction())
{
    session.SaveOrUpdate(something);
    // ...


    SqlBulkCopy bulkCopy = new SqlBulkCopy(
    (SqlConnection)session.Connection,
    SqlBulkCopyOptions.CheckConstraints | SqlBulkCopyOptions.FireTriggers,
    ???transaction???
    );
    //...

    transaction.Commit();
}

I know that I could use TransactionScope or do it otherwise. But I insist on this pattern. Let's pretend that for the sake of independent DB access (if I extract and inject arbitrary bulk insert operation). Is there a way how to get SqlTransaction instance out of NHibernate.ITransaction ?

Thanks

Answer 1

Unsurprisingly, Ayende tackled this one as well , but it's pretty grody.

The gist of it is that you know you can enlist normal ADO.NET IDbCommand instances in the NHibernate transaction, like so:

var cmd = new SqlCommand ();
if (session.Transaction != null && session.Transaction.IsActive)
    session.Transaction.Enlist (cmd);

But SqlBulkCopy isn't an IDbCommand , and that particular constructor requires a SqlTransaction (so you've already skipped the boat on provider-independence anyways). So cheat -- your example might look something like this:

using (var session = NHibernateHelper.OpenSession ())
using (var transaction = session.BeginTransaction ()) {
    using (var cmd = new SqlCommand ()) {
        transaction.Enlist (cmd);

        var bulk = new SqlBulkCopy ((SqlConnection)session.Connection,
                                    SqlBulkCopyOptions.CheckConstraints | SqlBulkCopyOptions.FireTriggers,
                                    (SqlTransaction)cmd.Transaction);
    }
    // ...
    transaction.Commit ();
}

You'll undoubtedly want some error-checking, safe casts, etc. in there. I'm not aware of a more modern/less scary way to do this, unfortunately (even to get an IDbTransaction from an ITransaction ).

Answer 2

Check this post from Ayene:
http://ayende.com/Blog/archive/2009/08/22/nhibernate-perf-tricks.aspx

He shows how you can do that using both options either NHibernate StatelessSession or SqlBulkCopy. It shows a sample code like this:

    var dt = new DataTable("Users");
    dt.Columns.Add(new DataColumn("Id", typeof(int)));
    dt.Columns.Add(new DataColumn("Password", typeof(byte[])));
    dt.Columns.Add(new DataColumn("Username"));
    dt.Columns.Add(new DataColumn("Email"));
    dt.Columns.Add(new DataColumn("CreatedAt", typeof(DateTime)));
    dt.Columns.Add(new DataColumn("Bio"));

    for (int i = 0; i < count; i++)
    {
        var row = dt.NewRow();
        row["Id"] = i;
        row["Password"] = Guid.NewGuid().ToByteArray();
        row["Username"] ="User " + i;
        row["Email"] = i + "@example.org";
        row["CreatedAt"] =DateTime.Now;
        row["Bio"] =  new string('*', 128);
        dt.Rows.Add(row);
    }

using (var connection =
 ((ISessionFactoryImplementor)sessionFactory).ConnectionProvider.GetConnection())
{
    var s = (SqlConnection)connection;
    var copy = new SqlBulkCopy(s);
    copy.BulkCopyTimeout = 10000;
    copy.DestinationTableName = "Users";
    foreach (DataColumn column in dt.Columns)
    {
        copy.ColumnMappings.Add(column.ColumnName, column.ColumnName);
    }
    copy.WriteToServer(dt);
}