title: Adding user, IP Address to PostgreSQL logging
body: <p>I assume I'm missing something easy in the docs, but for the life of me I can't figure out how to add the user id and IP address of the machine running the query in the log files in PostgreSQL.  I can see it clearly in <code>pg_stat_activity</code> once it's happening, but when doing post mortems on database issues, it would be very helpful to see these in the logs.</p>
  
  <p>I doubt it matters, but my server startup is this:</p>
  
  <pre><code>$BIN/pg_ctl -D /apps/pgdata9.5.0 -l /apps/logs/postgresql start
  </code></pre>
  
  <p>I was hoping there was a setting in postgresql.conf, but if there it it's eluded me.</p>