Re: How clear the cache on postgresql?

2017-11-24 17:55 GMT+01:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> bricklen <bricklen(at)gmail(dot)com> writes:
>
> > If you are on a (non-production) *nix server you can use:
> > sync && echo 3 > /proc/sys/vm/drop_caches​
>
> You would also need to restart the postmaster, to get rid of whatever
> is in Postgres' shared buffers.
>

And restart postgres first, otherwise the shutdown checkpoint will
repopulate
some of the buffers you just dropped via drop_caches.

On Fri, Nov 24, 2017 at 9:09 AM, hmidi slim <hmidi(dot)slim2(at)gmail(dot)com> wrote:

> I execute the command sync && echo 3 > /proc/sys/vm/drop_caches​ but I
> still got buffers hit added to that buffers read now.Why I got the buffers
> hit?
>

Please don't top post in this mailling list.

If the same buffer is accessed repeatedly in a query, then some of those
accesses will be from the cache even if it were completely cold to start
with.

Cheers,

Jeff