Re: parallelism and sorting

On Tue, Nov 24, 2015 at 8:59 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
>
> One idea about parallel sort is that perhaps if multiple workers feed
> data into the sort, they can each just sort what they have and then
> merge the results.

Sounds like a good approach for parallel sorting, however small extension
to it that could avoid merging the final results is that workers allocated
for sort will perform range-based sorting. A simple example to sort integers
from 1-100 will be, worker-1 will be responsible for sorting any integer
between 1-50 and worker-2 will be responsible for sorting integers from
51-100 and then master backend just needs to ensure that it first returns
the tuples from worker-1 and then from worker-2. I think it has some
similarity to your idea-5 (use of repartition), but not exactly same.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com