title: When we need return value from trigger procedure?
body: <p>Documentation about trigger procedures  (<a href="https://www.postgresql.org/docs/9.6/static/plpgsql-trigger.html" rel="noreferrer">https://www.postgresql.org/docs/9.6/static/plpgsql-trigger.html</a>) says: "A trigger function must return either NULL or a record/row".</p>
  
  <p>Example</p>
  
  <pre><code>CREATE TRIGGER my_trigger
  AFTER INSERT ON table_name
  FOR EACH ROW EXECUTE PROCEDURE some_trigger_function();
  </code></pre>
  
  <p>Suppose <code>some_trigger_function()</code> returns record/row, I understood that procedure body is called and executed on this event, on this table, and so on... but where returns value this procedure?</p>
  
  <p>Question is: when we use that returned value? why we needed this value at all? Can you give little example/explanation, which uses this returned value?</p>