Извините конечно, а что влом уже читать как апгрейдится?
тынц

Вот отсюда

E.1.2. Migration to version 8.1
A dump/restore using pg_dump is required for those wishing to migrate data from any previous release.

The 8.0 release announced that the to_char() function for intervals would be removed in 8.1. However, since no better API has been suggested, to_char(interval) has been enhanced in 8.1 and will remain in the server.

Observe the following incompatibilities:
...

и далее по тексту