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From "RPost" <rp0...@pacbell.net>
Subject Re: [jira] Created: (DERBY-133) Autocommit turned false and rollbacks
Date Tue, 25 Jan 2005 16:44:47 GMT
Thanks for the detailed code sample. The sample, of course, does not show
the foreign key being built or more than one thread, but I assume it was
provided to enable the recreation of the problem.

Since the dual-thread code wasn't posted I have a few questions:

1. Is each thread doing a 'println' that shows the record being inserted?

2. When does each thread do its commit?

3. Does your code ensure that the salary insert thread is
executing/committing before the employee insert thread? How are you
controlling the execution order of the threads? Does the system time show
the salary commit occuring prior to the employee commit?


----- Original Message ----- 
From: "Anil Rao (JIRA)" <derby-dev@db.apache.org>
To: <derby-dev@db.apache.org>
Sent: Tuesday, January 25, 2005 8:07 AM
Subject: [jira] Created: (DERBY-133) Autocommit turned false and rollbacks


> Autocommit turned false and rollbacks
> -------------------------------------
>
>          Key: DERBY-133
>          URL: http://issues.apache.org/jira/browse/DERBY-133
>      Project: Derby
>         Type: Improvement
>   Components: Store
>     Versions: 10.1.0.0
>  Environment: Windows XP Environment
>     Reporter: Anil Rao
>
>
> I have two tables Employee and Salary. Salary is a child of Employee table
with a foriegn key with 1 to many relationship between the two tables.
>
> I have in my java file connection to the database, with set Autocommit
being false. When I have two connection threads inserting on to employee and
salary tables. I made a an insert into salary table and then to employee
table, with that employee not in the employee, the insert went through fine.
>
> Then I made an insert into employee table and it went fine.
>
> In the next set of transaction I had the salary table insert going through
fine and then the employee insert did not go through, and the transaction on
the employee insert was rolled back but not the salary table insert.
>
> Can anyone please help me whether any setting I need to do to make this
work correctly.
>
> Example of the java code and tables script is as follows.
>
> Script to create tables.
> Create Employee and Salary tables in any derby database.
> Script is as below.
> CREATE TABLE employee( empid INTEGER NOT NULL,
> full_name VARCHAR(30) NOT NULL,
> salary DECIMAL(10,2) NOT NULL );
>
>
> CREATE TABLE salary(
> empid INTEGER NOT NULL,
> pay_date DATE NOT NULL);
>
> alter table employee add CONSTRAINT emp_pk PRIMARY KEY (empid)
>
> ALTER TABLE salary ADD CONSTRAINT salary_fk1
> FOREIGN KEY (empid)
> REFERENCES employee(empid)
> ;
>
> -- Java Code for inserts.
> import java.sql.Connection;
>
> /*
>  * Embedded Connection.
>  */
> import java.sql.DriverManager;
> import java.sql.ResultSet;
> import java.sql.SQLException;
> import java.sql.Statement;
>
> import java.util.Properties;
>
> public class EmConst
> {
>     /* the default framework is embedded*/
>     public String framework = "embedded";
>     public String driver = "org.apache.derby.jdbc.EmbeddedDriver";
>     public String protocol = "jdbc:derby:";
>
>     public static void main(String[] args)
>     {
>         new EmConst().go(args);
>     }
>
>     void go(String[] args)
>     {
>         /* parse the arguments to determine which framework is desired*/
>         parseArguments(args);
>
>         System.out.println("SimpleApp starting in " + framework + "
mode.");
>
>         try
>         {
>             /*
>                The driver is installed by loading its class.
>                In an embedded environment, this will start up Derby, since
it is not already running.
>              */
>             Class.forName(driver).newInstance();
>             System.out.println("Loaded the appropriate driver.");
>
>             Connection conn = null;
>             Properties props = new Properties();
>             props.put("user", "");
>             props.put("password", "");
>
>             /*
>                The connection specifies create=true to cause
>                the database to be created. To remove the database,
>                remove the directory derbyDB and its contents.
>                The directory derbyDB will be created under
>                the directory that the system property
>                derby.system.home points to, or the current
>                directory if derby.system.home is not set.
>              */
>             conn = DriverManager.getConnection(protocol +
>                     "Emp;create=true", props);
>
>             System.out.println("Connected to and created database
derbyDB");
>
>             conn.setAutoCommit(false);
>
>             /*
>                Creating a statement lets us issue commands against
>                the connection.
>              */
>             Statement s = conn.createStatement();
>
>             /*
>                We create a table, add a few rows, and update one.
>              */
>             s.execute("create TABLE employee(empid INTEGER NOT
NULL,full_name VARCHAR(30) NOT NULL,salary DECIMAL(10,2) NOT NULL )");
>             System.out.println("Created table Employee");
>             s.execute("create TABLE salary(empid INTEGER NOT NULL,pay_date
DATE NOT NULL)");
>             System.out.println("Created table Salary");
>
>             s.execute("insert into employee values (100,'John',100)");
>             System.out.println("Inserted John Record");
>             s.execute("insert into salary values (100,'01/01/2003')");
>             System.out.println("Inserted John Salary");
>             s.execute("insert into salary values (200,'01/01/2003')");
>             System.out.println("Inserted Pat Salary");
>         s.execute("insert into employee values (200,'Patt','200')");
>             System.out.println("Inserted Pat Record");
>             s.execute("select count(*) from salary");
>             System.out.println("Count of salary");
>             s.execute("select count(*) from employee");
>             System.out.println("Count of employee");
>
>
>             /*
>                We end the transaction and the connection.
>              */
>             conn.commit();
>             conn.close();
>             System.out.println("Committed transaction and closed
connection");
>
>             /*
>                In embedded mode, an application should shut down Derby.
>                If the application fails to shut down Derby explicitly,
>                the Derby does not perform a checkpoint when the JVM shuts
down, which means
>                that the next connection will be slower.
>                Explicitly shutting down Derby with the URL is preferred.
>                This style of shutdown will always throw an "exception".
>              */
>             boolean gotSQLExc = false;
>
>             if (framework.equals("embedded"))
>             {
>                 try
>                 {
>
DriverManager.getConnection("jdbc:derby:;shutdown=true");
>                 }
>                 catch (SQLException se)
>                 {
>                     gotSQLExc = true;
>                 }
>
>                 if (!gotSQLExc)
>                 {
>                     System.out.println("Database did not shut down
normally");
>                 }
>                 else
>                 {
>                     System.out.println("Database shut down normally");
>                 }
>             }
>         }
>         catch (Throwable e)
>         {
>             System.out.println("exception thrown:");
>
>             if (e instanceof SQLException)
>             {
>                 printSQLError((SQLException) e);
>             }
>             else
>             {
>                 e.printStackTrace();
>             }
>         }
>
>         System.out.println("SimpleApp finished");
>     }
>
>     static void printSQLError(SQLException e)
>     {
>         while (e != null)
>         {
>             System.out.println(e.toString());
>             e = e.getNextException();
>         }
>     }
>
>     private void parseArguments(String[] args)
>     {
>         int length = args.length;
>
>         for (int index = 0; index < length; index++)
>         {
>             if (args[index].equalsIgnoreCase("jccjdbcclient"))
>             {
>                 framework = "jccjdbc";
>                 driver = "com.ibm.db2.jcc.DB2Driver";
>                 protocol = "jdbc:derby:net://localhost:1527/";
>             }
>         }
>     }
> }
>
>
> -- Comments
> We have oracle, sqlserver and mysql handle the rollbacks using a seperate
rollback mechanism say rollback segment in oracle, temp in sqlserver and
mysql also has some of these functionality. Yes we can handle the exception
in the application but the problem is in the example we have two tables one
parent one child, and it is inserting into child without the parent, causing
inconsistency in database. The Database must take care of this. Derby needs
to handle this type of issue. The way this needs to be handled is that all
transactions must be logged in that are not yet committed into a rollback
file. This can be removed on commit. If there is any failover then the
entire set of transactions are rolled back, and the file contains the
transaction.that can be applied after making the right modifications and
committed.
>
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