On Thu, Apr 2, 2015 at 5:34 PM, Peter Geoghegan <p...@heroku.com> wrote: > I think it's explained by the pre-check for sorted input making the > number of comparisons exactly n -1. As I pointed out to Tomas, if you > put a single, solitary unsorted element at the end, the abbreviated > version is then 8x faster (maybe that was in relation to a slightly > different case, but the pattern is the same). So this case isn't an > argument against datum abbreviation, or even abbreviation in general, > but rather an argument against using strxfrm() in general (which for > example the GCC docs strongly recommend for sorting lists of strings). > It's a bad argument, IMV. This sort is already extremely fast.
OK, I see. > The changes that Andrew > took issue with are utterly insignificant. Great. Then you will be utterly indifferent to which version gets committed. > Also, the changes that Andrew didn't mention are clearly appropriate. > In particular, the comments on the SortKeys variable being used by > every case except the hash case and datum case should still be updated > to reflect that that's only true for the hash case now. On that point, I agree. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
