title: How to invoke a trigger on all rows manually in postgres
body: <p>My trigger is defined the following way:</p>
  
  <pre><code>CREATE TRIGGER update_contract_finished_at
      AFTER INSERT OR DELETE OR UPDATE OF performed_on
      ON task
      FOR EACH ROW
      EXECUTE PROCEDURE update_contract_finished_at_function();
  </code></pre>
  
  <p>I now want to evoke this trigger to set the variables which are updated by the trigger. How do I do that?</p>
  
  <p>Something like</p>
  
  <pre><code>for each row in task
  execute procedure update_contract_finished_at_function();
  </code></pre>
  
  <p>I know I can update with a standard update set statement. I also want to verifiy that my trigger works on all the data correctly. </p>