On Fri, June 26, 2009 11:39 am, Tom Lane wrote: > to...@tuxteam.de writes: >> On Fri, Jun 26, 2009 at 05:03:11PM +0200, Dimitri Fontaine wrote: >>> It's becoming somewhat tricky, but maybe the test to do for the >>> optimisation to get used is n >= threshold && str[n-6] == 0x20, Ã la >>> 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) > > We're trying to avoid adding cycles to the optimization-is-useless case. > The more expensive this test gets, the slower the unoptimizable case > becomes. >
Yeah. Like you, I like the idea of a switch based on string length. I would suggest a cutoff of something like 36 (length of the string representation of a UUID). But maybe that will miss lots of optimisable cases like address fields. I guess those people should really be using varchar(n) anyway. cheers andrew -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
