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Re: 2nd Level Buffer Cache

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: rsmogura <rsmogura(at)softperience(dot)eu>
Cc: Kevin Grittner <kevin(dot)grittner(at)wicourts(dot)gov>, PG Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 2nd Level Buffer Cache
Date: 2011-03-18 17:08:41
Message-ID: 1300467989-sup-3338@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
Excerpts from rsmogura's message of vie mar 18 11:57:48 -0300 2011:

>  Actually idea of this patch was like this:
>  Some operations requires many buffers, PG uses "clock sweep" to get 
>  next free buffer, so it may overwrite index buffer. From point of view 
>  of good database design We should use indices, so purging out index from 
>  cache will affect performance.

The BufferAccessStrategy stuff was written to solve this problem.

>  As the side effect I saw that this 2nd level keeps pg_* indices in 
>  memory too, so I think to include 3rd level cache for some pg_* tables.

Keep in mind that there's already another layer of caching (see
syscache.c) for system catalogs on top of the buffer cache.

-- 
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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