From: | Matthew Wakeling <matthew(at)flymine(dot)org> |
---|---|
To: | Eliot Gable <egable+pgsql-performance(at)gmail(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Highly Efficient Custom Sorting |
Date: | 2010-07-02 14:50:55 |
Message-ID: | alpine.DEB.2.00.1007021548080.2534@aragorn.flymine.org |
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Lists: | pgsql-performance |
> On Fri, Jul 2, 2010 at 12:08 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I'm guessing from tea leaves, but the impression I got from Eliot's
>> description is that he's using plpgsql functions as sort comparators.
>> It's not surprising that that sucks performance-wise compared to having
>> the equivalent logic in C/C++ functions used as comparators on the
>> client side. plpgsql is no speed demon. Best fix might be to code the
>> comparators as C functions on the server side.
On Fri, 2 Jul 2010, Eliot Gable wrote:
> I guess the real question is, is a generic C sorting function my only real
> alternative?
Sounds to me like you are not really listening. You don't need to code an
entire sorting algorithm in C, as Postgres already has a pretty good one
of those. All you need to do is implement a comparator of some kind.
Inserting C functions into Postgres is pretty easy, especially on the
level of comparators.
Matthew
--
For those of you who are into writing programs that are as obscure and
complicated as possible, there are opportunities for... real fun here
-- Computer Science Lecturer
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