Re: Hash partitioning. - Mailing list pgsql-hackers

From Markus Wanner
Subject Re: Hash partitioning.
Date
Msg-id 51CCB25F.6060106@bluegap.ch
Whole thread Raw
In response to Re: Hash partitioning.  (Jeff Janes <jeff.janes@gmail.com>)
List pgsql-hackers
On 06/27/2013 11:13 PM, Jeff Janes wrote:
> Wouldn't any IO system being used on a high-end system be fairly good
> about making this work through interleaved read-ahead algorithms?

To some extent, certainly. It cannot possibly get better than a fully
sequential load, though.

> That sounds like it would be much more susceptible to lock contention,
> and harder to get bug-free, than dividing into bigger chunks, like whole
> 1 gig segments.  

Maybe, yes. Splitting a known amount of work into equal pieces sounds
like a pretty easy parallelization strategy. In case you don't know the
total amount of work or the size of each piece in advance, it gets a bit
harder. Choosing chunks that turn out to be too big certainly hurts.

Regards

Markus Wanner



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