Editing PostgreSQL/MediaWiki

PostgreSQL is used as our database for a number of reasons, from stability to compatibility with other apps to support for JSONB values. 

However, it is clearly not the most popular choice of database for Mediawiki, so we do make some workarounds to support this unique use case. These mods are noted below.

=== PostgreSQL with UNIX Sockets ===

As noted in the Mediawiki tutorial, you generally connect to the PostgreSQL over a TCP connection, and use <code>md5</code> password authentication. 

However, ''if the PostgreSQL database is on the same server'', it's a better idea to dispense with the TCP overhead and connect to the UNIX socket directly. 

First, make sure that you've set a password for the <code>postgres</code> superuser, so you can log into it without using <code>peer</code> authentication, which we are going to switch to <code>md5</code>.

<pre>
$ sudo su # must become root to become postgres user first
# su postgres
$ psql
postgres=# \password
Enter new password:
Enter it again:
postgres=#
</pre>

Next, we need to enable <code>md5</code> authentication to the UNIX socket. On PostgreSQL 9.6 on Debian, edit the file <code>/etc/postgresql/9.6/main/pg_hba.conf</code> and change the following lines to match the below:

<pre>
# "local" is for Unix domain socket connections only
local   all             all                                     md5
# IPv4 local connections:
host    all             all             127.0.0.1/32            md5
# IPv6 local connections:
host    all             all             ::1/128                 md5
</pre>

On Debian, the PostgreSQL UNIX Socket is at <code>/var/run/postgresql/.s.PGSQL.5432</code>, so in LocalSettings.php set these following lines (make sure to comment out <code>$wgDBPort</code>, which is not needed)

<pre>
## Database settings
$wgDBtype = "postgres";
$wgDBserver = "/var/run/postgresql/.s.PGSQL.5432"; # UNIX port path

# Postgres specific settings
#$wgDBport = "5432"; # disable this
</pre>

{{Note|Obviously if the PostgreSQL database is on another server you have to use TCP and not UNIX sockets to communicate with it, so just expose the port on that server and put the IP in <code>$wgDBServer</code> in LocalSettings.php.}}