title: PostgreSQL 9.2 set enable_nestloop has no effect
body: <p>I try to changing nestloop</p>
  
  <pre><code>set enable_nestloop=1
  </code></pre>
  
  <p>When I look</p>
  
  <pre><code>show enable_nestloop;
   enable_nestloop 
  -----------------
   on
  (1 row)
  </code></pre>
  
  <p>all is ok. But it has no effect.
  If changing this param in config file and then reload config from cli, all work fine. 
  Why <em>set</em> not working for me?</p>