Re: How does PG know if data is in memory?

The discussions I've seen indicated that, in use, tablespaces were at the database level, but, yes, the docs do say that a table can be assigned to a defined tablespace. What I still can't find is syntax which establishes buffers/caches/whatever and assigns them to tablespaces. Without that, I'm not sure what benefit there is to tablespaces, other than a sort of RAID-lite.

Robert

---- Original message ----
>Date: Tue, 12 Oct 2010 08:34:23 -0400
>From: pgsql-performance-owner(at)postgresql(dot)org (on behalf of Robert Haas <robertmhaas(at)gmail(dot)com>)
>Subject: Re: [PERFORM] How does PG know if data is in memory?
>To: gnuoytr(at)rcn(dot)com
>Cc: pgsql-performance(at)postgresql(dot)org
>
>On Mon, Oct 11, 2010 at 11:11 PM, <gnuoytr(at)rcn(dot)com> wrote:
>> An approach that works can be found in DB2, and likely elsewhere.
>>
>> The key is that tablespaces/tables/indexes/buffers are all attached through the bufferpool (the DB2 term).  A tablespace/bufferpool match is defined.  Then tables and indexes are assigned to the tablespace (and implicitly, the bufferpool).  As a result, one can effectively pin data in memory.  This is very useful, but not low hanging fruit to implement.
>>
>> The introduction of rudimentary tablespaces is a first step.  I assumed that the point was to get to a DB2-like structure at some point.  Yes?
>
>We already have tablespaces, and our data already is accessed through
>the buffer pool.
>
>--
>Robert Haas
>EnterpriseDB: http://www.enterprisedb.com
>The Enterprise PostgreSQL Company
>
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