Update script must check the schema version before trying to update

[Nicklas Nordborg]

If the schema version is higher than expected the update script must stop. This would happen if trying to run the update script from a previous release. See mailing list for more info:

​http://sourceforge.net/mailarchive/forum.php?thread_id=31614751&forum_id=12992

[Nicklas Nordborg]

I checked the code and the first place to check the schema version is in the HibernateUtil.createStaticTables() method. The call sequence for an install/update is:

InitDb.main()
Install.createTables()
HibernateUtil.createStaticTables()

The HibernateUtil.createStaticTables() method already checks if the database is emtpy or not. It should not be too difficult to add a check in the "if (update)" part to check the schema version. I think it is safe to use the Application.getSchemaVersion() method to find out the current schema version. Compare the value against the Install.NEW_SCHEMA_VERSION constant. If the NEW_SCHEMA_VERSION is lower than the current schema version the update should stop. Make sure to handle the case where Application.getSchemaVersion() returns -1 (in which case the update should also stop).

[Martin Svensson]

(In [3122]) Fixes #487. Update script must check the schema version before trying to update.