Re: Inlining comparators as a performance optimisation

On 21 September 2011 15:50, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
>> I'm not against making things faster, it's just that I haven't seen
>> solid evidence yet that this will help. Just provide a best-case test
>> case for this that shows a huge improvement, and I'll shut up. If the
>> improvement is only modest, then let's discuss how big it is and whether
>> it's worth the code ugliness this causes.

Fair enough.

> The other question that I'm going to be asking is whether it's not
> possible to get most of the same improvement with a much smaller code
> footprint.

That's a reasonable question, and I hope to be able to come up with a
good answer.

> I continue to suspect that getting rid of the SQL function
> impedance-match layer (myFunctionCall2Coll etc) would provide most of
> whatever gain is to be had here, without nearly as large a cost in code
> size and maintainability, and with the extra benefit that the speedup
> would also be available to non-core datatypes.

I'm fairly surprised that your view on that is mostly or entirely
unchanged, even after I've demonstrated a considerable performance
advantage from a macro-based qsort implementation over my OS vendor's
c std lib qsort(), using an isolated test-case, that does not have
anything to do with that impedance mismatch. I'm not sure why you
doubt that the same thing is happening within tuplesort.

--
Peter Geoghegan       http://www.2ndQuadrant.com/
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