It could be cheaper, if the testing is done for many SELECT queries sequentially - you need to flush dirty buffers just once pretty much.
-Vladimir Churyukin On Wed, Jun 14, 2023 at 7:43 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Thomas Munro <thomas.mu...@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 >
