| From: | tomas(at)tuxteam(dot)de |
|---|---|
| To: | Dimitri Fontaine <dfontaine(at)hi-media(dot)com> |
| Cc: | Jeremy Kerr <jk(at)ozlabs(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Gurjeet Singh <singh(dot)gurjeet(at)gmail(dot)com> |
| Subject: | Re: [PATCH] backend: compare word-at-a-time in bcTruelen |
| Date: | 2009-06-26 15:29:06 |
| Message-ID: | 20090626152906.GA948@tomas |
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| Lists: | pgsql-hackers |
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On Fri, Jun 26, 2009 at 05:03:11PM +0200, Dimitri Fontaine wrote:
> Le 26 juin 09 à 14:47, Jeremy Kerr a écrit :
>> For the new function to be faster, we need to know that there are more
>> than 6 (on average, depending on alignment) trailing spaces.
>
> It's becoming somewhat tricky, but maybe the test to do for the
> optimisation to get used is n >= threshold && str[n-6] == 0x20, àla
> Boyer/Moore?
That's cute. What about comparing the last aligned word which completely
fits in the buffer? Something along the lines of (assuming four-byte
words)
* (int*) (4 * ((int) &buf[0]) / 4)
(now that's an ugly one, but you know what I mean?)
Regards
- -- tomás
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