Re: An idea on faster CHAR field indexing
От | Giles Lean |
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Тема | Re: An idea on faster CHAR field indexing |
Дата | |
Msg-id | 12346.961663663@nemeton.com.au обсуждение исходный текст |
Ответ на | Re: An idea on faster CHAR field indexing (Tom Lane <tgl@sss.pgh.pa.us>) |
Список | pgsql-hackers |
> Interesting. That certainly suggests strxfrm could be a loser for > a database index too, but I agree it'd be nice to see some actual > measurements rather than speculation. > > What locale(s) were you using when testing your sort code? I suspect > the answers might depend on locale quite a bit... I did a little more measurement today. It's still only annecdotal evidence -- I wasn't terribly rigorous -- but here are my results. My data file consisted of ~660,000 lines and a total size of ~200MB. Each line had part descriptions in German and some uninteresting fields. I stripped out the uninteresting fields and read the file calling calling strxfrm() for each line. I recorded the total input bytes and the total bytes returned by strxfrm(). HP-UX 11.00 de_DE.roman8 locale: input bytes: 179647811 result bytes: 1447833496 (increase factor 8.05) Solaris 2.6 de_CH locale: input bytes: 179647811 result bytes: 1085875122 (increase factor 6.04) I didn't time the test program on Solaris, but on HP-UX this program took longer to run than a simplistic qsort() using strcoll() does, and my comparison sort program has to write the data out as well, which the strxfrm() calling program didn't do. Regards, Giles
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