Forum OpenACS Development: Re: OpenACS 5.9 Complaints about PostgreSQL 8.4
Thanks for the information on HEAD. Just FYI, the version number on HEAD already include 5.10.x.
So we'll need to patch OpenACS 5.9 to work with PostgreSQL 8.4, because we need to test with quite a lot of existing installations.
The recommended action is certainly to upgrade pg8.4 to 9.*. this is typically just a pg-dump + pg-restore (since pg 9.0, there is pg_upgrade). Pg documentation  contains an example for using pg_upgrade from 8.4.