Thank you for this infos, I wasn't sure about this, now, at least, I know that this is not possible. On the other hand, even the most experienced database programmer / administrator when upgrading a production environment can't be 100% sure about whether the application,will fail or not. Of course, testing is the only way to ensure that everything will be as smooth as possible but a real safety net would be to establish a common dump file format across different PG versions. I will keep searching ... and testing of course :)
My understanding is that dumps are not backwards compatible. Any dumps created with a Version 8.* pg_dump cannot be used for any older versions. If you want "play it safe" you should create a new server for the postgresql version 8.1 to preform validation tests with your front-ends. After you are satisfied that everything works well you can replace the version 7 production server with version 8. If you would like a safety net beyond this you could contact one of the PostgreSQL consulting companies to walk you through the integration of V.8.1 into your projection system. Regards, Richard Broersma Jr.
