title: See and clear Postgres caches/buffers?
body: <p>Sometimes I run a Postgres query and it takes 30 seconds. Then, I immediately run the same query and it takes 2 seconds. It appears that Postgres has some sort of caching. Can I somehow see what that cache is holding? Can I force all caches to be cleared for tuning purposes?</p>
  <p>I'm basically looking for a Postgres version of the following SQL Server command:</p>
  <pre><code>DBCC FREEPROCCACHE
  DBCC DROPCLEANBUFFERS
  </code></pre>
  <p>But I would also like to know how to see what is actually contained in that buffer.</p>