Обсуждение: Flush Shared Buffer Cache
Hi,
Can anyone help me out with how to flush out Shared Buffer Cache in Postgres.
One way would be to restart the database, but I would like to avoid that.
Regards,
Suvankar Roy
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Suvankar Roy wrote: > > Hi, > > Can anyone help me out with how to flush out Shared Buffer Cache in > Postgres. > > One way would be to restart the database, but I would like to avoid that. AFAIK, that's the only way. Is there a reason that you need to dump the shared buffers? Perhaps if we knew what you were trying to accomplish we could provide you with a suitable solution that doesn't require a restart... -- Chander Ganesan Open Technology Group, Inc. One Copley Parkway, Suite 210 Morrisville, NC 27560 919-463-0999/877-258-8987 http://www.otg-nc.com Expert PostgreSQL, PostGIS, and other Open Source training delivered worldwide.
Hi Chander,
Actually I am trying to figure out how much execution time any query is taking is taking when executed for the first time.
Because once a query is executed for the first time, the query plan, data buffer is cached so subsequently time taken is much lower.
For this, I want to have the Shared buffer cache flushed to note the initial execution time.
Is my understanding correct here ?
Regards,
Suvankar Roy
Chander Ganesan <chander@otg-nc.com> 07/15/2009 08:48 PM |
|
Suvankar Roy wrote:
>
> Hi,
>
> Can anyone help me out with how to flush out Shared Buffer Cache in
> Postgres.
>
> One way would be to restart the database, but I would like to avoid that.
AFAIK, that's the only way.
Is there a reason that you need to dump the shared buffers? Perhaps if
we knew what you were trying to accomplish we could provide you with a
suitable solution that doesn't require a restart...
--
Chander Ganesan
Open Technology Group, Inc.
One Copley Parkway, Suite 210
Morrisville, NC 27560
919-463-0999/877-258-8987
http://www.otg-nc.com
Expert PostgreSQL, PostGIS, and other Open Source training delivered worldwide.
ForwardSourceID:NT00004B0E
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Suvankar Roy <suvankar.roy@tcs.com> wrote: > Actually I am trying to figure out how much execution time any query > is taking is taking when executed for the first time. > > Because once a query is executed for the first time, the query plan, > data buffer is cached so subsequently time taken is much lower. > > For this, I want to have the Shared buffer cache flushed to note > the initial execution time. > > Is my understanding correct here ? Keep in mind that the OS cache will also normally have a significant amount of PostgreSQL data cached. For "uncached" timings, you will need to purge this, too. Of course, for real-life production benchmarks the most meaningful timings are normally those taken within your actual production mix, with all the caching and resource competition which goes along with that. -Kevin