| From: | Peter Geoghegan <peter(at)2ndquadrant(dot)com> |
|---|---|
| To: | Marti Raudsepp <marti(at)juffo(dot)org> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [PATCH] Make skipped sort explicit in EXPLAIN ANALYZE |
| Date: | 2012-05-25 14:39:24 |
| Message-ID: | CAEYLb_U2NY9ZbeXuUhqY3dqDxVuumSavdKbOqxYTd29Ew-+TpA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 25 May 2012 15:19, Marti Raudsepp <marti(at)juffo(dot)org> wrote:
> I understand where you're coming from, but personally I think the
> current output is more confusing: "Gee Postgres is stupid, it's
> sorting when there's nothing to sort!"
>
> But let's wait for a third opinion.
I agree with Tom. The idea that you "sort when there's nothing to
sort" is not confusing. Textbook implementations of recursive sorting
algorithms explicitly have a notion of sorting one element, by simply
recognising that one element must already be sorted. For example, look
at the quicksort pseudocode here:
http://en.wikipedia.org/wiki/Quicksort
--
Peter Geoghegan http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services
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