One good way to check if you have contrib modules installed is to see if the pgbench program is available. That's one of the few contrib components that installs a full program, rather than just scripts you can use. Here's a UNIX example of checking for pgbench:

$ pgbench -V
    pgbench (PostgreSQL) 9.6

If you're using an RPM or DEB packaged version of PostgreSQL, as would be the case on many Linux systems, the optional postgresql-contrib package contains all of the contrib modules and their associated installer scripts. You may have to add that package using yum, apt-get, or a similar mechanism if it isn't installed already. On Solaris, the package is named SUNWpostgr-contrib.

If you're not sure where your system PostgreSQL contrib modules are installed, you can use a filesystem utility to search for them. The locate works well for this purpose on many UNIX-like systems, as does the find command. The file search utilities available on the Windows Start menu will work. A sample file you could look for is pg_buffercache.sql which will be used in the upcoming Chapter 5, Memory for Database Caching, on memory allocation. Here's where you might find the file on some of the platforms that PostgreSQL supports:

Building your own PostgreSQL from source code can be a straightforward exercise on some platforms, if you have the appropriate requirements already installed on the server. Details are documented at http://www.postgresql.org/docs/current/static/install-procedure.html.

After building the main server code, you'll also need to compile contrib modules like pg_buffercache yourself too. Here's an example of how that would work, presuming that your PostgreSQL destination is /usr/local/postgresql and there's a directory under there named that source you put the source code into (this is not intended to be a typical or recommended structure you should use):

$ cd /usr/local/postgresql/source
    $ cd contrib/pg_buffercache/
    $ make
    $ make install
    /bin/mkdir -p '/usr/local/postgresql/lib/postgresql'
    /bin/mkdir -p '/usr/local/postgresql/share/postgresql/contrib'
    /bin/sh ../../config/install-sh -c -m 755  pg_buffercache.so
      '/usr/local/postgresql/lib/postgresql/pg_buffercache.so'
    /bin/sh ../../config/install-sh -c -m 644
      ./uninstall_pg_buffercache.sql
      '/usr/local/postgresql/share/postgresql/contrib'
    /bin/sh ../../config/install-sh -c -m 644 pg_buffercache.sql
      '/usr/local/postgresql/share/postgresql/contrib'

It's also possible to build and install all the contrib modules at once by running make and make install from the contrib directory. Note that some of these have more extensive source code build requirements. The uuid-ossp module is an example of a more challenging one to compile yourself.

While some contrib programs, such as pgbench, are directly executable, most are utilities that you install into a database in order to add extra features to it.

As an example, to install the pg_buffercache module into a database named abc, the following command line would work (assuming the RedHat location for the file):

    $ psql -d abc -f /usr/share/postgresql/contrib/pg_buffercache.sql 

You could instead use the pgAdmin III GUI management utility, which is bundled with the Windows installer for PostgreSQL, instead of the command line:

You can do a quick test of whether the module installed on any type of system by running the following quick query:

    SELECT * FROM pg_buffercache;

If any results come back, the module was installed. Note that pg_buffercache will only be installable and usable by database superusers.

PostgreSQL introduces another way to install contrib module, called extensions. If any contrib module build with the extension specification which includes:

Let's look at the following commands: