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From "Kathey Marsden (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DERBY-6053) Client should use a prepared statement rather than regular statement for Connection.setTransactionIsolation
Date Fri, 25 Jan 2013 15:03:12 GMT
Kathey Marsden created DERBY-6053:
-------------------------------------

             Summary: Client should use a prepared statement rather than regular statement
for Connection.setTransactionIsolation
                 Key: DERBY-6053
                 URL: https://issues.apache.org/jira/browse/DERBY-6053
             Project: Derby
          Issue Type: Improvement
            Reporter: Kathey Marsden


o.a.d.client.am.Connection setTransactionIsolation() uses a Statement which  it builds up
each time for setTransactionIsolation()  is called.

private Statement setTransactionIsolationStmt = null;
...
setTransactionIsolationStmt =
                    createStatementX(java.sql.ResultSet.TYPE_FORWARD_ONLY,
                            java.sql.ResultSet.CONCUR_READ_ONLY,
                            holdability());
....
 private void setTransactionIsolationX(int level)
...
            setTransactionIsolationStmt.executeUpdate(
                "SET CURRENT ISOLATION = " + levelString);


It would be better for performance and also for avoid possible garbage collection issues,
to have a single prepared statement with a parameter marker. 

The program below shows repeated calls to setTransactionIsolation.

import java.sql.*;
import java.net.*;
import java.io.*;
import org.apache.derby.drda.NetworkServerControl;

/**
 * Client template starts its own NetworkServer and runs some SQL against it.
 * The SQL or JDBC API calls can be modified to reproduce issues
 * 
 */public class SetTransactionIsolation {
    public static Statement s;
    
    public static void main(String[] args) throws Exception {
        try {
            // Load the driver. Not needed for network server.
            
            Class.forName("org.apache.derby.jdbc.ClientDriver");
            // Start Network Server
            startNetworkServer();
            // If connecting to a customer database. Change the URL
            Connection conn = DriverManager
                    .getConnection("jdbc:derby://localhost:1527/wombat;create=true");
            // clean up from a previous run
            s = conn.createStatement();
            try {
                s.executeUpdate("DROP TABLE T");
            } catch (SQLException se) {
                if (!se.getSQLState().equals("42Y55"))
                    throw se;
            }

            for (int i = 0; i < 50000; i++) {
		conn.setTransactionIsolation(Connection.TRANSACTION_REPEATABLE_READ);
		conn.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE);

	    }
            
            // rs.close();
            // ps.close();
            runtimeInfo();
            conn.close();
            // Shutdown the server
            shutdownServer();
        } catch (SQLException se) {
            while (se != null) {
                System.out.println("SQLState=" + se.getSQLState()
                        + se.getMessage());
                se.printStackTrace();
                se = se.getNextException();
            }
        }
    }
    
    /**
     * starts the Network server
     * 
     */
    public static void startNetworkServer() throws SQLException {
        Exception failException = null;
        try {
            
            NetworkServerControl networkServer = new NetworkServerControl(
                    InetAddress.getByName("localhost"), 1527);
            
            networkServer.start(new PrintWriter(System.out));
            
            // Wait for the network server to start
            boolean started = false;
            int retries = 10; // Max retries = max seconds to wait
            
            while (!started && retries > 0) {
                try {
                    // Sleep 1 second and then ping the network server
                    Thread.sleep(1000);
                    networkServer.ping();
                    
                    // If ping does not throw an exception the server has
                    // started
                    started = true;
                } catch (Exception e) {
                    retries--;
                    failException = e;
                }
                
            }
            
            // Check if we got a reply on ping
            if (!started) {
                throw failException;
            }
        } catch (Exception e) {
            SQLException se = new SQLException("Error starting network  server");
            se.initCause(failException);
            throw se;
        }
    }
    
    public static void shutdownServer() throws Exception {
        NetworkServerControl networkServer = new NetworkServerControl(
                InetAddress.getByName("localhost"), 1527);
        networkServer.shutdown();
    }
    
    public static void runtimeInfo() throws Exception {
        NetworkServerControl networkServer = new NetworkServerControl(
                InetAddress.getByName("localhost"), 1527);
        System.out.println(networkServer.getRuntimeInfo());
    }
    
}


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