Re: Inlining comparators as a performance optimisation

On Wed, Sep 21, 2011 at 7:51 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> On 21.09.2011 02:53, Peter Geoghegan wrote:
>>
>> C stdlib quick-sort time elapsed: 2.092451 seconds
>> Inline quick-sort time elapsed: 1.587651 seconds
>>
>> Does *that* look attractive to you?
>
> Not really, to be honest. That's a 25% speedup in pure qsorting speed. How
> much of a gain in a real query do you expect to get from that, in the best
> case? There's so many other sources of overhead that I'm afraid this will be
> lost in the noise. If you find a query that spends, say, 50% of its time in
> qsort(), you will only get a 12.5% speedup on that query. And even 50% is
> really pushing it - I challenge you to find a query that spends any
> significant amount of time qsorting integers.

How about almost every primary index creation?

Don't really see a reason for the negativity here. If you use that
argument no performance gain is worth it because all workloads are
mixed.

This is a marvellous win, a huge gain from a small, isolated and
easily tested change. By far the smallest amount of additional code to
sorting we will have added and yet one of the best gains.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
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