title: sSpark structured streaming PostgreSQL updatestatebykey
body: <p>How to update state of <strong>OUTPUT TABLE</strong> by Spark structured streaming computation triggered by changes in <strong>INPUT</strong> PostgreSQL table?</p>
  
  <p>As a real life scenario USERS table has been updated by <code>user_id = 0002</code>, how to trigger Spark computation for that user only and write / update results to another table?</p>