/*******************************************************************************
* Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Created July 9, 2008 - ailitchev
* bug 240210: Tests: Several LRG tests hang on Sybase
* Changed Dec 17, 2008 - etang
* Move the class from org.eclipse.persistence.testing.tests.unitofwork
* to org.eclipse.persistence.testing.framework
******************************************************************************/
package org.eclipse.persistence.testing.framework;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashMap;
import org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor;
import org.eclipse.persistence.sessions.SessionEvent;
import org.eclipse.persistence.sessions.SessionEventAdapter;
import org.eclipse.persistence.sessions.server.ServerSession;
import org.eclipse.persistence.testing.framework.TestProblemException;
/*
* According to http://manuals.sybase.com/onlinebooks/group-as/asg1250e/sqlug/@Generic__BookTextView/53713;pt=52735/*
* The SQL92 standard defines four levels of isolation for transactions.
* Each isolation level specifies the kinds of actions that are not permitted while concurrent transactions are executing.
* Higher levels include the restrictions imposed by the lower levels:
*
* Level 0 - ensures that data written by one transaction represents the actual data.
* It prevents other transactions from changing data that has already been modified
* (through an insert, delete, update, and so on) by an uncommitted transaction.
* The other transactions are blocked from modifying that data until the transaction commits.
* However, other transactions can still read the uncommitted data, which results in dirty reads.
*
* Level 1 - prevents dirty reads.
* Such reads occur when one transaction modifies a row, and a second transaction reads that row before the first transaction commits the change.
* If the first transaction rolls back the change, the information read by the second transaction becomes invalid.
* This is the default isolation level supported by Adaptive Server.
* ....
*
* Apparently Sybase versions 12.5 and 15 has Level 1 set as default.
* That causes several tests to hang: these tests begin transaction, update a row,
* then (before the transaction has been committed) attempt to read the row through another connection.
*
* To allow these reads to go through (and read the uncommitted data) connection isolation level
* should be temporary switched to Level 0.
*
* This class switches the acquired connection to Level 0 and then sets back the original isolation level before connection is released.
*
* Note that for the above scenario only read connection require Level 0.
*
* This solution works only on Sybase 15 but fails on Sybase 12.5 with:
* com.sybase.jdbc3.jdbc.SybSQLException: The optimizer could not find a unique index which it could use to perform an isolation level 0 scan on table 'RESPONS'.
*
*/
public class SybaseTransactionIsolationListener extends SessionEventAdapter {
HashMap<Connection, Integer> connections = new HashMap<Connection, Integer>();
public static int requiredVersion = 15;
// verify that it's version 15 or higher - this doesn't work with version 12.5
public static boolean isDatabaseVersionSupported(ServerSession serverSession) {
DatabaseAccessor accessor = (DatabaseAccessor)serverSession.allocateReadConnection();
int version;
try {
String strVersion = accessor.getConnectionMetaData().getDatabaseProductVersion();
int iStart = strVersion.indexOf("/") + 1;
int iEnd = strVersion.indexOf(".");
String strIntVersion = strVersion.substring(iStart, iEnd);
version = Integer.parseInt(strIntVersion);
} catch (SQLException ex) {
throw new TestProblemException("failed to obtain database version number", ex);
}
return version >= requiredVersion;
}
public void postAcquireConnection(SessionEvent event) {
Connection conn = ((DatabaseAccessor)event.getResult()).getConnection();
Statement stmt1 = null;
Statement stmt2 = null;
ResultSet result = null;
Integer isolationLevel;
try {
stmt1 = conn.createStatement();
result = stmt1.executeQuery("select @@isolation");
result.next();
isolationLevel = new Integer(result.getInt(1));
if(isolationLevel > 0) {
// If conn1 began transaction and updated the row (but hasn't committed the transaction yet),
// then conn2 should be able to read the original (not updated) state of the row.
// Without this conn2 reading the row hangs on Sybase.
stmt2 = conn.createStatement();
stmt2.execute("set transaction isolation level 0");
stmt2.close();
connections.put(conn, isolationLevel);
}
} catch (SQLException sqlException) {
throw new TestProblemException("postAcquireConnection failed. ", sqlException);
} finally {
if(result != null) {
try {
result.close();
} catch (SQLException ex) {
// Ignore
}
}
if(stmt1 != null) {
try {
stmt1.close();
} catch (SQLException ex) {
// Ignore
}
}
if(stmt2 != null) {
try {
stmt2.close();
} catch (SQLException ex) {
// Ignore
}
}
}
}
public void preReleaseConnection(SessionEvent event) {
Connection conn = ((DatabaseAccessor)event.getResult()).getConnection();
Statement stmt = null;
try {
Integer isolationLevel = connections.remove(conn);
if (isolationLevel != null){
// reset the original transaction isolation.
stmt = conn.createStatement();
stmt.execute("set transaction isolation level " + isolationLevel);
stmt.close();
}
} catch (SQLException sqlException) {
throw new TestProblemException("preReleaseConnection failed. ", sqlException);
} finally {
if(stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
// Ignore
}
}
}
}
}