title: Does Postgres provide a command to flush buffer cache?
body: <p>Hi
     Sometimes I need to do some SQL tuning task, I usually do such tests on my test db.
  After I excute a sql statments, I want to flush the buffer cache which containing SQL
  statements and sql result, just like the command in Oracle "Alter system flush buffer_cache"<br>
  Is PG server provide a commond of this?</p>