Manual:PostgreSQL

Currently, version 8.0 or greater of Postgres is required. In addition, you must have tsearch2 and the Pl/Pgsql language installed for the wiki to function correctly.

tsearch2
The tsearch2 module needs to be installed to do the full-text searching of your wiki. How to install it depends a lot on how your Postgres installation is set up. Generally, once you have tsearch2 installed via your packaging system (e.g. postgresql-contrib-8.2.deb), you need to install tsearch2 into the database you are going to use. This generally involves running the tsearch2.sql script as a superuser inside the database you want to install to. For example, if your tsearch2.sql file is located at /usr/share/postgresql/contrib/tsearch2.sql, you have a superuser named postgres, and you are adding tsearch2 to the wikidb database, the following command can be used:

psql -U postgres wikidb -f /usr/share/postgresql/contrib/tsearch2.sql

Note that this command may issue some warnings, but they are generally safe to ignore. You can test if tsearch2 is successfully installed by running:

psql -U postgres wikidb -c "select relname from pg_class where relname ~ '^pg_ts'

You should see four tables starting with "pg_ts". If not, then tsearch was probably not installed.