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Re: Parallel query execution

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>,Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Parallel query execution
Date: 2013-01-17 02:44:53
Message-ID: 20130117024453.GB683@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Jan 16, 2013 at 05:04:05PM -0800, Jeff Janes wrote:
> On Tuesday, January 15, 2013, Stephen Frost wrote:
> 
>     * Gavin Flower (GavinFlower(at)archidevsys(dot)co(dot)nz) wrote:
>     > How about being aware of multiple spindles - so if the requested
>     > data covers multiple spindles, then data could be extracted in
>     > parallel. This may, or may not, involve multiple I/O channels?
> 
>     Yes, this should dovetail with partitioning and tablespaces to pick up
>     on exactly that.  
> 
> 
> I'd rather not have the benefits of parallelism be tied to partitioning if we
> can help it.  Hopefully implementing parallelism in core would result in
> something more transparent than that.

We will need a way to know we are not saturating the I/O channel with
random I/O that could have been sequential if it was single-threaded. 
Tablespaces give us that info;  not sure what else does.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +


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