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From "Daniel John Debrunner (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-421) starting an XA transaction resets the isolation level set with SET CURRENT ISOLATION
Date Wed, 24 Aug 2005 17:08:24 GMT
    [ http://issues.apache.org/jira/browse/DERBY-421?page=comments#action_12319883 ] 

Daniel John Debrunner commented on DERBY-421:
---------------------------------------------

A few questions on the patch:

1) In BrokeredConnection.setState() the method getIsolationUptoDate() is called. This new
method updates the BrokeredConnection state according to the state of the underlying connection,
but the purpose and description of the setState() method is the opposite. Thus this method
call looks out pf place. Additional comments indicating why it is here would be useful.

2) The new field isolationLevelSetUsingSQLorJDBC in GenericLanguageConnectionContext seems
to have similar functionality to the existing field isolationLevelExplicitlySet. Are two fields
really required? Usually multiple similar state fields is a recipe for bugs.

3)  The number of new methods to acheive this functionality seems high, I wonder if there
is a simpler approach, it would be easier to tell if you could expand on your comment  'And
this flag is later used to keep the isolation level state information uptodate in BrokeredConnection.'
Could you comment on exactly when this flag is used to reset the state?

> starting an XA transaction resets the isolation level set with SET CURRENT ISOLATION
> ------------------------------------------------------------------------------------
>
>          Key: DERBY-421
>          URL: http://issues.apache.org/jira/browse/DERBY-421
>      Project: Derby
>         Type: Sub-task
>   Components: JDBC
>     Reporter: Kathey Marsden
>     Assignee: Mamta A. Satoor
>  Attachments: derby421XAIsolation082205.txt
>
> When an XA Transaction is started the isolation level set with SET CURRENT ISOLATION
gets reset to CS.
> Embedded setTransactionIsolation  does not have this problem but this problem is the
root cause of DERBY-414 because client implements setTransactionIsolation by sending SET CURRENT
ISOLATION
> $ java TestSetCurrentIsolation
> Database product: Apache Derby
> Database version: 10.2.0.0 alpha
> Driver name:      Apache Derby Embedded JDBC Driver
> Driver version:   10.2.0.0 alpha
> SET CURRENT ISOLATION = UR
> CURRENT ISOLATION: UR
> getTransactionIsolation:TRANSACTION_READ_UNCOMMITTED:1
> Isolation level after xa start
> CURRENT ISOLATION: CS
> getTransactionIsolation:TRANSACTION_READ_COMMITTED:2
> $
> import java.sql.*;
> import javax.sql.*;
> import javax.transaction.xa.*;
> public class TestSetCurrentIsolation
> {
>     public static void main(String[] args) throws Throwable
>     {
>         try
>         {
>              final org.apache.derby.jdbc.EmbeddedXADataSource ds =
>              new org.apache.derby.jdbc.EmbeddedXADataSource();
>              ds.setDatabaseName("C:\\drivers\\derby\\databases\\SCHEDDB");
>              ds.setUser("dbuser1");
>              ds.setPassword("******");
>             XAConnection xaConn = ds.getXAConnection();
>             Connection conn = xaConn.getConnection();
>             conn.setAutoCommit(true);
>             System.out.println("Database product: " + conn.getMetaData().getDatabaseProductName());
>             System.out.println("Database version: " + conn.getMetaData().getDatabaseProductVersion());
>             System.out.println("Driver name:      " + conn.getMetaData().getDriverName());
>             System.out.println("Driver version:   " + conn.getMetaData().getDriverVersion());
>             Statement stmt = conn.createStatement();
>             System.out.println("SET CURRENT ISOLATION = UR");
>             stmt.executeUpdate("SET CURRENT ISOLATION = UR");
>             showIsolationLevel(conn);
>             conn.setAutoCommit(false);
>             XAResource xaRes = xaConn.getXAResource();
>             Xid xid = new TestXid(1,(byte) 32, (byte) 32);
>             xaRes.start(xid, XAResource.TMNOFLAGS);
>             System.out.println("Isolation level after xa start");
>             showIsolationLevel(conn);
>             
>             xaRes.end(xid, XAResource.TMSUCCESS);
>             xaRes.rollback(xid);
>             conn.close();
>             xaConn.close();
>         }
>         catch (SQLException sqlX)
>         {
>             System.out.println("Error on thread 1.");
>             do sqlX.printStackTrace();
>             while ((sqlX = sqlX.getNextException()) != null);
>         }
>         catch (Throwable th)
>         {
>             System.out.println("Error on thread 1.");
>             do th.printStackTrace();
>             while ((th = th.getCause()) != null);
>         }
>     }
> 	/**
> 	 * @param conn
> 	 * @throws SQLException
> 	 */
> 	private static void showIsolationLevel(Connection conn) throws SQLException {
> 		PreparedStatement ps = conn.prepareStatement("VALUES CURRENT ISOLATION");
> 		ResultSet rs = ps.executeQuery();
> 		//ResultSet rs = conn.createStatement().executeQuery("VALUES CURRENT ISOLATION");
> 		rs.next();
> 		System.out.println("CURRENT ISOLATION: " +  rs.getString(1));
> 		System.out.println("getTransactionIsolation:" + 
> 					getIsoLevelName(conn.getTransactionIsolation()));						
> 	}
> 	
> 	public static String getIsoLevelName(int level)
> 	{
> 		switch (level) {
> 			case java.sql.Connection.TRANSACTION_REPEATABLE_READ:
> 				return "TRANSACTION_REAPEATABLE_READ:" + level;
> 					
> 			case java.sql.Connection.TRANSACTION_READ_COMMITTED:
> 				return "TRANSACTION_READ_COMMITTED:" + level;
> 			case java.sql.Connection.TRANSACTION_SERIALIZABLE:
> 				return "TRANSACTION_SERIALIZABLE:" + level;
> 			case java.sql.Connection.TRANSACTION_READ_UNCOMMITTED:
> 				return "TRANSACTION_READ_UNCOMMITTED:" + level;
> 		}
> 		return "UNEXPECTED_ISO_LEVEL";
> 	}
> }

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