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.
>