I wrote: > One of the points of the talk I linked to is "if doing the sensible thing makes things worse, try something silly instead".
For item pointers, it made sense to try doing math to reduce the number of branches. That made things worse, so let's try the opposite: Increase the number of branches so we do less math. In the attached patch (applies on top of your 0012 and a .txt to avoid confusing the CF bot), I test a new comparator with this approach, and also try a wider range of thresholds. The thresholds don't seem to make any noticeable difference with this data type, but the new comparator (cmp=ids below) gives a nice speedup in this test: # SELECT test_sort_itemptr(); NOTICE: [traditional qsort] order=random, threshold=7, cmp=32, test=0, time=4.964657 NOTICE: [traditional qsort] order=random, threshold=7, cmp=32, test=1, time=5.185384 NOTICE: [traditional qsort] order=random, threshold=7, cmp=32, test=2, time=5.058179 NOTICE: order=random, threshold=7, cmp=std, test=0, time=2.810627 NOTICE: order=random, threshold=7, cmp=std, test=1, time=2.804940 NOTICE: order=random, threshold=7, cmp=std, test=2, time=2.800677 NOTICE: order=random, threshold=7, cmp=ids, test=0, time=1.692711 NOTICE: order=random, threshold=7, cmp=ids, test=1, time=1.694546 NOTICE: order=random, threshold=7, cmp=ids, test=2, time=1.692839 NOTICE: order=random, threshold=12, cmp=std, test=0, time=2.687033 NOTICE: order=random, threshold=12, cmp=std, test=1, time=2.681974 NOTICE: order=random, threshold=12, cmp=std, test=2, time=2.687833 NOTICE: order=random, threshold=12, cmp=ids, test=0, time=1.666418 NOTICE: order=random, threshold=12, cmp=ids, test=1, time=1.666188 NOTICE: order=random, threshold=12, cmp=ids, test=2, time=1.664176 NOTICE: order=random, threshold=16, cmp=std, test=0, time=2.574147 NOTICE: order=random, threshold=16, cmp=std, test=1, time=2.579981 NOTICE: order=random, threshold=16, cmp=std, test=2, time=2.572861 NOTICE: order=random, threshold=16, cmp=ids, test=0, time=1.699432 NOTICE: order=random, threshold=16, cmp=ids, test=1, time=1.703075 NOTICE: order=random, threshold=16, cmp=ids, test=2, time=1.697173 NOTICE: order=random, threshold=32, cmp=std, test=0, time=2.750040 NOTICE: order=random, threshold=32, cmp=std, test=1, time=2.744138 NOTICE: order=random, threshold=32, cmp=std, test=2, time=2.748026 NOTICE: order=random, threshold=32, cmp=ids, test=0, time=1.677414 NOTICE: order=random, threshold=32, cmp=ids, test=1, time=1.683792 NOTICE: order=random, threshold=32, cmp=ids, test=2, time=1.701309 NOTICE: [traditional qsort] order=increasing, threshold=7, cmp=32, test=0, time=2.543837 NOTICE: [traditional qsort] order=increasing, threshold=7, cmp=32, test=1, time=2.290497 NOTICE: [traditional qsort] order=increasing, threshold=7, cmp=32, test=2, time=2.262956 NOTICE: order=increasing, threshold=7, cmp=std, test=0, time=1.033052 NOTICE: order=increasing, threshold=7, cmp=std, test=1, time=1.032079 NOTICE: order=increasing, threshold=7, cmp=std, test=2, time=1.041836 NOTICE: order=increasing, threshold=7, cmp=ids, test=0, time=0.367355 NOTICE: order=increasing, threshold=7, cmp=ids, test=1, time=0.367428 NOTICE: order=increasing, threshold=7, cmp=ids, test=2, time=0.367384 NOTICE: order=increasing, threshold=12, cmp=std, test=0, time=1.004991 NOTICE: order=increasing, threshold=12, cmp=std, test=1, time=1.008045 NOTICE: order=increasing, threshold=12, cmp=std, test=2, time=1.010778 NOTICE: order=increasing, threshold=12, cmp=ids, test=0, time=0.370944 NOTICE: order=increasing, threshold=12, cmp=ids, test=1, time=0.368669 NOTICE: order=increasing, threshold=12, cmp=ids, test=2, time=0.370100 NOTICE: order=increasing, threshold=16, cmp=std, test=0, time=1.023682 NOTICE: order=increasing, threshold=16, cmp=std, test=1, time=1.025805 NOTICE: order=increasing, threshold=16, cmp=std, test=2, time=1.022005 NOTICE: order=increasing, threshold=16, cmp=ids, test=0, time=0.365398 NOTICE: order=increasing, threshold=16, cmp=ids, test=1, time=0.365586 NOTICE: order=increasing, threshold=16, cmp=ids, test=2, time=0.364807 NOTICE: order=increasing, threshold=32, cmp=std, test=0, time=0.950780 NOTICE: order=increasing, threshold=32, cmp=std, test=1, time=0.949920 NOTICE: order=increasing, threshold=32, cmp=std, test=2, time=0.953239 NOTICE: order=increasing, threshold=32, cmp=ids, test=0, time=0.367866 NOTICE: order=increasing, threshold=32, cmp=ids, test=1, time=0.372179 NOTICE: order=increasing, threshold=32, cmp=ids, test=2, time=0.371115 NOTICE: [traditional qsort] order=decreasing, threshold=7, cmp=32, test=0, time=2.317475 NOTICE: [traditional qsort] order=decreasing, threshold=7, cmp=32, test=1, time=2.323446 NOTICE: [traditional qsort] order=decreasing, threshold=7, cmp=32, test=2, time=2.326714 NOTICE: order=decreasing, threshold=7, cmp=std, test=0, time=1.022270 NOTICE: order=decreasing, threshold=7, cmp=std, test=1, time=1.015133 NOTICE: order=decreasing, threshold=7, cmp=std, test=2, time=1.016367 NOTICE: order=decreasing, threshold=7, cmp=ids, test=0, time=0.386884 NOTICE: order=decreasing, threshold=7, cmp=ids, test=1, time=0.388397 NOTICE: order=decreasing, threshold=7, cmp=ids, test=2, time=0.386328 NOTICE: order=decreasing, threshold=12, cmp=std, test=0, time=0.993594 NOTICE: order=decreasing, threshold=12, cmp=std, test=1, time=0.995031 NOTICE: order=decreasing, threshold=12, cmp=std, test=2, time=0.995320 NOTICE: order=decreasing, threshold=12, cmp=ids, test=0, time=0.391243 NOTICE: order=decreasing, threshold=12, cmp=ids, test=1, time=0.391938 NOTICE: order=decreasing, threshold=12, cmp=ids, test=2, time=0.392478 NOTICE: order=decreasing, threshold=16, cmp=std, test=0, time=1.006240 NOTICE: order=decreasing, threshold=16, cmp=std, test=1, time=1.009817 NOTICE: order=decreasing, threshold=16, cmp=std, test=2, time=1.010281 NOTICE: order=decreasing, threshold=16, cmp=ids, test=0, time=0.386388 NOTICE: order=decreasing, threshold=16, cmp=ids, test=1, time=0.385801 NOTICE: order=decreasing, threshold=16, cmp=ids, test=2, time=0.384484 NOTICE: order=decreasing, threshold=32, cmp=std, test=0, time=0.959647 NOTICE: order=decreasing, threshold=32, cmp=std, test=1, time=0.958833 NOTICE: order=decreasing, threshold=32, cmp=std, test=2, time=0.960234 NOTICE: order=decreasing, threshold=32, cmp=ids, test=0, time=0.403014 NOTICE: order=decreasing, threshold=32, cmp=ids, test=1, time=0.393329 NOTICE: order=decreasing, threshold=32, cmp=ids, test=2, time=0.395659 -- John Naylor EDB: http://www.enterprisedb.com
itemptr-cmp-blockids.patch
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