It looks like that gnucash on openSUSE 13.1 has been correctly configured with the option --enable-dbi
but when you install gnucash it does not come automatically with the libdbi-drivers-dbd-pgsql driver package so you only will see the save to XML option in gnucash.
gnucash doc link: 2.5. Storing your financial data

In order to be able to save your data via postgresql you will have to install the following packages:

Code:
# zypper in gnucash postgresql92-server libdbi-drivers-dbd-pgsql

# rpm -q gnucash postgresql92-server libdbi-drivers-dbd-pgsql
gnucash-2.4.13-2.1.3.x86_64
postgresql92-server-9.2.4-4.1.3.x86_64
libdbi-drivers-dbd-pgsql-0.9.0-2.1.2.x86_64
PS: if you wan to use sqllite or mysql the packages to install are

Code:
# zypper se -t package libdbi-drivers
S | Name                       | Summary                      | Type   
--+----------------------------+------------------------------+--------
  | libdbi-drivers-dbd-mysql   | MySQL driver for libdbi      | package
i | libdbi-drivers-dbd-pgsql   | PostgreSQL driver for libdbi | package
i | libdbi-drivers-dbd-sqlite3 | SQLite3 driver for libdbi    | package
I've not found much user feedback about using gnucash with postgresql on openSUSE.
I'm tempted to move my personal XML file to postgresql, any advice ?
Feel free to post if you are using such configuration or already did the switch from XML to postgresql.

Cheers