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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6053) Client should use a prepared statement rather than regular statement for Connection.setTransactionIsolation
Date Wed, 27 Feb 2013 04:44:14 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13587994#comment-13587994
] 

Mamta A. Satoor commented on DERBY-6053:
----------------------------------------

I am working on backporting the 2 commits that went in for this jira into 10.9 codelines.
But the declaration of isolationLevelPreparedStmts includes type parameters as shown below
    final private HashMap<String, PreparedStatement> 
        isolationLevelPreparedStmts = 
            new HashMap<String, PreparedStatement>();

This code when compiled in 10.9 gives following compile time error
    [javac] C:\p4clients\svn10.9\client1\10.9\java\client\org\apache\derby\client\am\Connection.java:91:
generics are not supported in -source 1.4
    [javac] (use -source 5 or higher to enable generics)
    [javac]     final private HashMap<String, PreparedStatement>
    [javac]                          ^

I know there are other clases in 10.9 that include type parameters during HashMap declaration
eg org.apache.derby.iapi.jdbc.FailedProperties40 but build.xml has been modified to compile
them with compilerLevel16 rather than 1.4. Is it ok to solve the compile time issue with Connection.java
by having it compile with compilerLevel16 or should I use the old style HashMap declaration(without
the type parameters) which is found scattered around in 10.9 codeline? Thanks for the help.
                
> 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
>          Components: Network Client
>            Reporter: Kathey Marsden
>            Assignee: Mamta A. Satoor
>             Fix For: 10.10.0.0
>
>         Attachments: derby-6053-01-aa-lintCheck.diff, DERBY6053_patch1_diff.txt
>
>
> 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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