Re: Re: Abbreviated keys for Numeric

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От Andrew Gierth
Тема Re: Re: Abbreviated keys for Numeric
Дата
Msg-id 87bnlkb1rs.fsf@news-spur.riddles.org.uk
обсуждение исходный текст
Ответ на Re: Abbreviated keys for Numeric (was: Re: B-Tree support function number 3 (strxfrm() optimization))  (Peter Geoghegan <pg@heroku.com>)
Ответы Re: Re: Abbreviated keys for Numeric  (Gavin Flower <GavinFlower@archidevsys.co.nz>)
Список pgsql-hackers
>>>>> "Peter" == Peter Geoghegan <pg@heroku.com> writes:
Peter> What I find particularly interesting about this patch is that itPeter> makes sorting numerics significantly
fasterthan even sortingPeter> float8 values,
 

Played some more with this. Testing on some different gcc versions
showed that the results were not consistent between versions; the latest
I tried (4.9) showed float8 as somewhat faster, while 4.7 showed float8
as slightly slower; the difference was all in the time of the float8
case, the time for numeric was virtually the same.

For one specific test query, taking the best time of multiple runs,

float8:   gcc4.7 = 980ms, gcc4.9 = 833ms
numeric:  gcc4.7 = 940ms, gcc4.9 = 920ms

(vs. 650ms for bigint on either version)

So honestly I think abbreviation for float8 is a complete red herring.

Also, I couldn't get any detectable benefit from inlining
DatumGetFloat8, though I may have to play more with that to be certain
(above tests did not have any float8-related modifications at all, just
the datum and numeric abbrevs patches).

-- 
Andrew (irc:RhodiumToad)



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