OracleCommand command, ExecuteNonQuery issue

Question

I have to clear certain tables in the oracle database however when I'm having issues with running the following code

public static void ClearDataTables(IList<string> tableNames)
        {
            string connectionString = "CONNECTIONSTRING";
            using (OracleConnection connection = new OracleConnection())
            {
                connection.ConnectionString = connectionString;
                connection.Open();
                foreach (string table in tableNames)
                {
                    OracleCommand command = connection.CreateCommand();
                    string sql = String.Format("DELETE FROM TOA_REPORTING.{0}", table);
                    command.CommandText = sql;
                    command.ExecuteNonQuery();
                }
                connection.Close();
            }
        }

I am calling this method with this list

ClearDataTables(new List<string> { "GROUP_DEFINITION", "GROUP_REPORT_EMAIL_LIST", "GROUP_EQUIPMENT_GROUP_STN_XREF"});

It runs the first two tables fine, however on the third one, it gets stuck and the application runs forever...

Funny thing is, when I switch "GROUP_REPORT_EMAIL_LIST" and "GROUP_EQUIPMENT_GROUP_STN_XREF" The application runs forever after the it hits the second table name.

So in conclusion, the function runs forever when it hits "GROUP_EQUIPMENT_GROUP_STN_XREF". I've verified that the SQL generated works by testing it out on toad.

Anyone else ran into this issue?

EDIT - The first two tables does indeed get cleared when it runs.

Solution

string connectionString = "CONNECTIONSTRING";
            using (OracleConnection connection = new OracleConnection(connectionString))
            {
                connection.Open();
                OracleCommand command = connection.CreateCommand();
                OracleTransaction trans = connection.BeginTransaction();
                command.Transaction = trans;
                foreach (string table in tableNames)
                {
                    string sql = String.Format("DELETE FROM TOA_REPORTING.{0}", table);
                    command.CommandText = sql;
                    command.ExecuteNonQuery();
                }
                trans.Commit();
            }

TRUNCATE would have been a very nice solution, however I do not have the privileges to do so!

Answer 1

Have you forgotten to commit your changes in Toad (or any other client)? An open transaction will cause it to wait indefinitely.

Answer 2

Is there a lot of data in that table? This would explain, why it takes so long to delete the data.
Anyway, I suggest to use TRUNC for clearing tables.

Answer 3

Large number of deletes can be very slow, especially if you run them in one transaction. If you don't need the transaction at all, use:

truncate table YourTable

If you do, split the delete over small-sized transactions. Basically run:

delete from YourTable where rownum < 100

until the table is empty. See for example this blog post.

Answer 4

I would probably write a stored procedure that does all of the deletions or truncations and invoke the SP once, rather than have a loop client-side.

EDIT: It would also be better not to create the command object inside the loop. Create it once outside the loop with a table-name parameter, and then invoke it feeding it a different parameter value with each iteration. But the SP is to be preferred.