Re: turn off caching for performance test
| От | Willy-Bas Loos |
|---|---|
| Тема | Re: turn off caching for performance test |
| Дата | |
| Msg-id | AANLkTimT19FjqVB+_kjevwbW9wG7FuV6O+nSrK0p6hYc@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: turn off caching for performance test ("Pierre C" <lists@peufeu.com>) |
| Ответы |
Re: turn off caching for performance test
|
| Список | pgsql-performance |
@Pierre: i know.. but first i'd have to find such a query from real-life. And also, i'm convinced that this query would be faster with a seqscan if the data wenen't cached.
@Arjen: thanks, that helps.
But that's only the OS cache. There's also the shared_buffers, which are a postgres specific thing.
I've found DISCARD in the manual, but that only influences a single session, not the shared buffers.
I reckon restarting the cluster should help, would it wipe out the cache? (pg_ctlcluster 8.3 main restart)
Or is there a more graceful way?
Cheers,
WBL
--
"Patriotism is the conviction that your country is superior to all others because you were born in it." -- George Bernard Shaw
@Arjen: thanks, that helps.
But that's only the OS cache. There's also the shared_buffers, which are a postgres specific thing.
I've found DISCARD in the manual, but that only influences a single session, not the shared buffers.
I reckon restarting the cluster should help, would it wipe out the cache? (pg_ctlcluster 8.3 main restart)
Or is there a more graceful way?
Cheers,
WBL
On Thu, Aug 26, 2010 at 7:37 PM, Pierre C <lists@peufeu.com> wrote:
3% isn't really significant. Especially if the new setting makes one query 100 times slower... Like a query which will, by bad luck, get turned into a nested loop index scan for a lot of rows, on a huge table which isn't in cache...The bitmap heap scan is 3% faster,
--
"Patriotism is the conviction that your country is superior to all others because you were born in it." -- George Bernard Shaw
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