On Sun, Feb 22, 2015 at 1:19 PM, Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > In short, this fixes all the cases except for the ASC sorted data. I > haven't done any code review, but I think we want this. > > I'll use data from the i5-2500k, but it applies to the Xeon too, except > that the Xeon results are more noisy and the speedups are not that > significant. > > For the 'text' data type, and 'random' dataset, the results are these: > > scale datum cost-model > ------------------------------- > 100000 328% 323% > 1000000 392% 391% > 2000000 96% 565% > 3000000 97% 572% > 4000000 97% 571% > 5000000 98% 570% > > The numbers are speedup vs. master, so 100% means exactly the same > speed, 200% means twice as fast. > > So while with 'datum' patch this actually caused very nice speedup for > small datasets - about 3-4x speedup up to 1M rows, for larger datasets > we've seen small regression (~3% slower). With the cost model fix, we > actually see a significant speedup (about 5.7x) for these cases.
Cool. > I haven't verified whether this produces the same results, but if it > does this is very nice. > > For 'DESC' dataset (i.e. data sorted in reverse order), we do get even > better numbers, with up to 6.5x speedup on large datasets. > > But for 'ASC' dataset (i.e. already sorted data), we do get this: > > scale datum cost-model > ------------------------------- > 100000 85% 84% > 1000000 87% 87% > 2000000 76% 96% > 3000000 82% 90% > 4000000 91% 83% > 5000000 93% 81% > > Ummm, not that great, I guess :-( You should try it with the data fully sorted like this, but with one tiny difference: The very last tuple is out of order. How does that look? -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers