Horton

Re: Inlining comparators as a performance optimisation

Peter Geoghegan <peter@2ndquadrant.com>

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From: Peter Geoghegan <peter@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, PG Hackers <pgsql-hackers@postgresql.org>
Date: 2011-09-21T15:43:31Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Speed up conversion of signed integers to C strings.

  2. Remove some unnecessary tests of pgstat_track_counts.

  3. Remove cvs keywords from all files.

  4. Code cleanup for function prototypes: change two K&R-style prototypes

  5. Use Min() instead of min() in qsort, for consistency and to avoid

  6. pgindent run for 8.2.

  7. Switch over to using our own qsort() all the time, as has been proposed

On 21 September 2011 15:50, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Heikki Linnakangas <heikki.linnakangas@enterprisedb.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/
PostgreSQL Development, 24x7 Support, Training and Services