Tom Lane <tgl@sss.pgh.pa.us> writes:
> Tourtounis Sotiris <tourtoun@csd.uoc.gr> writes:
> > I am sorry for my lack of good knowledge of English but i have previously
> > asked how during a session with the database server to empty the memory
> > buffers after any commited select/insert/delete in order to have an as
> > much as possible indicative execution time and explain facility for each
> > of them. Thank you for your willingness of help !!!
>
> Ah. In that case Josh's guess was right: you want to reboot the machine
> for each query. That's the only way AFAIK to flush the kernel's disk
> caches. Since Postgres relies on the kernel's disk buffering quite as
> much as its own buffering, just flushing Postgres' buffers wouldn't get
> you back to a standing start anyway.
Short of rebooting, you could umount and remount the partition that
$PGDATA lives on, if no other daemons are using it (and it's not your
root partition). At least on Linux, that'll flush out all the cached
blocks from that partition.
-Doug