| From: | Markus Wanner <markus(at)bluegap(dot)ch> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Kevin Grittner <kgrittn(at)ymail(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Yuri Levinsky <yuril(at)celltick(dot)com>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Hash partitioning. |
| Date: | 2013-06-27 21:45:03 |
| Message-ID: | 51CCB25F.6060106@bluegap.ch |
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| Lists: | 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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