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.
But I'm not sure that you'd be proving a lot by running your tests that
way --- it's not got a lot to do with realistic usage conditions. The
normal state of affairs for a database under load is that there is lots
of stuff in disk cache.
regards, tom lane