title: How disable postgresql "Cache" optimization?
body: <p>I'm trying to optimize my function. <br>
  The thing is when you run the query once you get one result. <br>
  Run the query a second time or third time the process time is much smaller.</p>
  
  <pre><code>SELECT  map.get_near_link(a.X, a.Y, a.azimuth)
  FROM traffic.avl;
  </code></pre>
  
  <p>First time 17 seg</p>
  
  <pre><code>Total query runtime: 17188 ms.
  801 rows retrieved.
  </code></pre>
  
  <p>Second time 11 seg</p>
  
  <pre><code>Total query runtime: 11406 ms.
  801 rows retrieved.
  </code></pre>
  
  <p>I'm guessing there is some kind of cache doing optimization behind scene.
  How can i disable this behavior so i can get a more realistic runtime value?</p>