Upgrade to 2.3 with MySQL causes error - Dialect class not found: bucket.dialect.MySQLDialect

When upgrading to 2.3 with MySQL, the following error occurs:

2007-01-06 18:43:28,115 WARN [main] [sf.hibernate.cfg.SettingsFactory] buildSettings No dialect set - using GenericDialect: Dialect class not found: bucket.dialect.MySQLDialect
2007-01-06 18:43:31,965 FATAL [main] [com.atlassian.upgrade.AbstractUpgradeManager] upgradeSchema Could not update schema.
com.atlassian.config.ConfigurationException: Cannot update schema
at bucket.core.persistence.hibernate.schema.SchemaHelper.updateSchemaIfNeeded(SchemaHelper.java:159)
at bucket.core.persistence.hibernate.schema.SchemaHelper.updateSchemaIfNeeded(SchemaHelper.java:142)
at com.atlassian.upgrade.AbstractUpgradeManager.upgradeSchema(AbstractUpgradeManager.java:137)
at com.atlassian.upgrade.AbstractUpgradeManager.upgrade(AbstractUpgradeManager.java:46)
at com.atlassian.confluence.upgrade.impl.DefaultUpgradeManager.upgrade(DefaultUpgradeManager.java:57)
at com.atlassian.upgrade.UpgradeLauncherServletContextListener.contextInitialized(UpgradeLauncherServletContextListener.java:26)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3729)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4187)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:608)
at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:535)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:470)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1122)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:310)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1021)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1013)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:709)
at org.apache.catalina.startup.Catalina.start(Catalina.java:551)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:294)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:432)
Caused by: net.sf.hibernate.HibernateException: Dialect class not found: bucket.dialect.MySQLDialect
at net.sf.hibernate.dialect.Dialect.getDialect(Dialect.java:396)
at net.sf.hibernate.tool.hbm2ddl.SchemaUpdate.<init>(SchemaUpdate.java:40)
at net.sf.hibernate.tool.hbm2ddl.SchemaUpdate.<init>(SchemaUpdate.java:35)
at bucket.core.persistence.hibernate.schema.SchemaHelper.updateSchemaIfNeeded(SchemaHelper.java:155)
... 29 more
2007-01-06 18:43:32,000 WARN [main] [core.persistence.hibernate.HibernateVersionHistoryDao] getLatestBuildNumber Unable to determine build number from database. If you are upgrading from a Confluence version prior to 2.3, this is expected: Table 'confluence.CONFVERSION' doesn't exist
2007-01-06 18:43:32,291 ERROR [main] [sf.hibernate.util.JDBCExceptionReporter] logExceptions Table 'confluence.BANDANA' doesn't exist