Question

I execute the following code via CLR, is there a reason why the message is not printed to the SQL Server, does it need to wait until the Stored Procedure returns all the rows (there is about 7 Billion rows to return)

    SqlCommand cmd = new SqlCommand();
        cmd.Connection = conn;
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.CommandText = "spCommand_Select_Rows_For_Delete";
        cmd.CommandTimeout = 41600;

        SqlDataReader reader = cmd.ExecuteReader();
        try
        {
            string strSQL = "";
            SqlContext.Pipe.Send(DateTime.Now.ToString() + " - Started working with ProductTable");

            while (reader.Read())
            {
                strSQL = "DELETE FROM ProductTable WHERE ProductId = " + reader["ProductId"].ToString();

                SqlCommand cmdDelete = new SqlCommand(strSQL, conn);

                cmdDelete.Connection = conn;
                cmdDelete.CommandTimeout = 20800;
                cmdDelete.ExecuteNonQuery();
            }

            SqlContext.Pipe.Send(DateTime.Now.ToString() + " - Completed working with ProductTable");
        }
        finally
        {
            // Always call Close when done reading.
            reader.Close();
        }

My Stored Procedure:

SELECT ProductId FROM ProductTable
    WHERE ProductInfoId IN
    (
    SELECT ProductInfoId from DeletedProducts
    )

Answer 1

Here’s how you delete 7 billion rows using a nice set based operation. You don’t abuse iterate through a datareader in CLR.

 SELECT 'Starting'
 WHILE ROWCOUNT <> 0
    DELETE TOP (1000000) P
    FROM  ProductTable P
    WHERE EXISTS (
        SELECT * from DeletedProducts DP WHERE P.ProductInfoId = DP.ProductInfoId
    )

For more, see this question Bulk DELETE on SQL Server 2008

But to answer your question, yes, SQL Server will not PRINT (which is what you’re doing) immediately