Upgrade between PostgreSQL versions
The probably easiest way to upgrade between PostgreSQL versions is as follows (described here from 9.4 to 9.5, based on the directory structure as provided by Mac Ports)
DATE=`date +"%Y-%m-%d"` # Dump all databases from pg 9.4 PGBIN=/opt/local/lib/postgresql94/bin sudo -u postgres $PGBIN/pg_dumpall | gzip -9 > ~/pg-dump-all-$DATE.gz
Then stop pg 9.4, start pg 9.5, then reload the dump:
# Restore all databases and roles from dump into pg 9.5 PGBIN=/opt/local/lib/postgresql95/bin gunzip < ~/pg-dump-all-$DATE.gz | $PGBIN/psql -U postgres
voilà, start OpenACS, and everything works fine.
In case there is a problem with restoring the dump in PostgreSQL 9.5 due to the "=>" operator of hstore, one has to update the version of hstore at least to 1.1 before dump/restore (the current version of hstore is 1.4; for details see hstore-upgrade).
In case, you want to upgrade your legacy OpenACS installation from PostgreSQL 8.* to 9, read upgrade-oacs-5-8.