Using SqlDataReader NextResult to improve performance

On database-driven websites it is commonplace to execute multiple database queries to generate just one page. For example, on the home page of an ecommerce website you might get a list of categories, a list of banner advertisements to display, a list of featured products, and a list of top selling products.

Generally it is common practice in this situation to execute four queries to get this data for display.

I wanted to investigate whether it was more efficient to put these multiple queries into one stored procedure and use the SqlDataReader's Next Result method to get the data all in one go.

My test case was to populate five Repeaters with data.

Test 1 is five different stored procedures and SqlDataReaders.

using (SqlConnection conn = new SqlConnection(Config.ConnString))
{
	conn.Open();

	String sql = "stp_Test1";

	using (SqlCommand comm = new SqlCommand(sql, conn))
	{
		comm.CommandType = CommandType.StoredProcedure;

		using (SqlDataReader reader = comm.ExecuteReader())
		{
			Repeater1.DataSource = reader;
			Repeater1.DataBind();
		}
	}

	sql = "stp_Test2";

	using (SqlCommand comm = new SqlCommand(sql, conn))
	{
		comm.CommandType = CommandType.StoredProcedure;

		using (SqlDataReader reader = comm.ExecuteReader())
		{
			Repeater2.DataSource = reader;
			Repeater2.DataBind();
		}
	}

	sql = "stp_Test3";

	using (SqlCommand comm = new SqlCommand(sql, conn))
	{
		comm.CommandType = CommandType.StoredProcedure;

		using (SqlDataReader reader = comm.ExecuteReader())
		{
			Repeater3.DataSource = reader;
			Repeater3.DataBind();
		}
	}

	sql = "stp_Test4";

	using (SqlCommand comm = new SqlCommand(sql, conn))
	{
		comm.CommandType = CommandType.StoredProcedure;

		using (SqlDataReader reader = comm.ExecuteReader())
		{
			Repeater4.DataSource = reader;
			Repeater4.DataBind();
		}
	}

	sql = "stp_Test5";

	using (SqlCommand comm = new SqlCommand(sql, conn))
	{
		comm.CommandType = CommandType.StoredProcedure;

		using (SqlDataReader reader = comm.ExecuteReader())
		{
			Repeater5.DataSource = reader;
			Repeater5.DataBind();
		}
	}
}

Test 2 is one stored procedure with the five queries retrieved using the one SqlDataReader and the use of the NextResult method.

using (SqlConnection conn = new SqlConnection(Config.ConnString))
{
	conn.Open();
				
	String sql = "stp_Test";

	using (SqlCommand comm = new SqlCommand(sql, conn))
	{
		comm.CommandType = CommandType.StoredProcedure;

		using (SqlDataReader reader = comm.ExecuteReader())
		{
			Repeater1.DataSource = reader;
			Repeater1.DataBind();

			reader.NextResult();
			Repeater2.DataSource = reader;
			Repeater2.DataBind();

			reader.NextResult();
			Repeater3.DataSource = reader;
			Repeater3.DataBind();

			reader.NextResult();
			Repeater4.DataSource = reader;
			Repeater4.DataBind();

			reader.NextResult();
			Repeater5.DataSource = reader;
			Repeater5.DataBind();
		}
	}
}

What was the result? On average test 2 executed around 40% quicker.

So the conclusion appears to be that thus technique is the way to go, but my testing does not take into consideration all factors (such as any impact due to having the reader open for longer) or what might happen on a very high traffic website.

Have you tried this technique? Please leave a comment with your results.