According to above link, PostgreSQL should be used with version specific driver, such as 9.3.x driver for 9.3 Server.
However, JIRA is shipped with postgresql-9.0-JDBC4 only.
1. JDBC41 is recommended for JAVA 1.7 and 1.8 instead of JDBC4
2. It is unclear that if user is recommended to install higher version of driver to match their PostgreSQL server version.