title: Who has any documents that about PostgreSQL background processes?
body: <p>Who has any documents that about PostgreSQL background processes?</p>
  
  <p>I'd like to learn the detail about these background processes:</p>
  
  <ul>
  <li>postgres: logger process                              </li>
  <li>postgres: writer process                              </li>
  <li>postgres: wal writer process                          </li>
  <li>postgres: autovacuum launcher process                 </li>
  <li>postgres: archiver process                            </li>
  <li>postgres: stats collector process  </li>
  </ul>