From: Sam R. <samruohola@yahoo.com>
To: Sergei Kornilov <sk@zsrv.org>
To: pgsql-performance@lists.postgresql.org <pgsql-performance@lists.postgresql.org>
Subject: Re: To keep indexes in memory, is large enough effective_cache_size enough?
Date: Wed, 19 Sep 2018 09:18:24 +0000 (UTC)
Message-ID: <1476619436.6435500.1537348704720@mail.yahoo.com> (raw)
In-Reply-To: <5456011537348252@sas1-fed4e4c8a570.qloud-c.yandex.net>
References: <1321418371.5650982.1537346138600.ref@mail.yahoo.com>
<1321418371.5650982.1537346138600@mail.yahoo.com>
<5456011537348252@sas1-fed4e4c8a570.qloud-c.yandex.net>
Sergei wrote:
> You can not pin any table or index to shared buffers.
Thanks, this is answer to my other question!
In our case, this might be an important feature.
(Index in memory, other data / columns not.)
> shared_buffers is cache for both tables and indexes pages.
Ok. So, we should set also shared_buffers big.
BR Sam
On Wednesday, September 19, 2018 12:10 PM, Sergei Kornilov <sk@zsrv.org> wrote:
Hi
effective_cache_size is not cache. It is just approx value for query planner: how many data can be found in RAM (both in shared_buffers and OS page cache)
> Q: Size of shared_buffers does not matter regarding keeping index in memory?
shared_buffers is cache for both tables and indexes pages. All data in tables and indexes are split to chunks 8 kb each - pages (usually 8kb, it can be redefined during source compilation).
Shared buffers cache is fully automatic, active used pages keeps in memory, lower used pages may be evicted. You can not pin any table or index to shared buffers.
regards, Sergei
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To: pgsql-performance@postgresql.org
Cc: samruohola@yahoo.com, sk@zsrv.org, pgsql-performance@lists.postgresql.org
Subject: Re: To keep indexes in memory, is large enough effective_cache_size enough?
In-Reply-To: <1476619436.6435500.1537348704720@mail.yahoo.com>
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