Thomas Munro <thomas.munro@gmail.com> writes:
> There are two levels of cache. If you're on Linux you can ask it to
> drop its caches by writing certain values to /proc/sys/vm/drop_caches.
> For PostgreSQL's own buffer pool, it would be nice if someone would
> extend the pg_prewarm extension to have a similar 'unwarm' operation,
> for testing like that. But one thing you can do is just restart the
> database cluster, or use pg_prewarm to fill its buffer pool up with
> other stuff (and thus kick out the stuff you didn't want in there).
But that'd also have to push out any dirty buffers. I'm skeptical
that it'd be noticeably cheaper than stopping and restarting the
server.
regards, tom lane