On Wed, Feb 15, 2023 at 3:02 PM David Rowley <dgrowle...@gmail.com> wrote: > > On Wed, 15 Feb 2023 at 17:23, John Naylor <john.nay...@enterprisedb.com> wrote: > > HEAD: > > > > 4 ^ 8: latency average = 113.976 ms > > 5 ^ 8: latency average = 783.830 ms > > 6 ^ 8: latency average = 3990.351 ms > > 7 ^ 8: latency average = 15793.629 ms > > > > Skip rechecking first key: > > > > 4 ^ 8: latency average = 107.028 ms > > 5 ^ 8: latency average = 732.327 ms > > 6 ^ 8: latency average = 3709.882 ms > > 7 ^ 8: latency average = 14570.651 ms
> Yeah, just a hack. My intention with it was just to prove we had a > problem because sometimes Sort -> Incremental Sort was faster than > Sort. Ideally, with your change, we'd see that it's always faster to > do the full sort in one go. It would be good to see your patch with > and without the planner hack patch to ensure sort is now always faster > than sort -> incremental sort. Okay, here's a rerun including the sort hack, and it looks like incremental sort is only ahead with the smallest set, otherwise same or maybe slightly slower: HEAD: 4 ^ 8: latency average = 113.461 ms 5 ^ 8: latency average = 786.080 ms 6 ^ 8: latency average = 3948.388 ms 7 ^ 8: latency average = 15733.348 ms tiebreaker: 4 ^ 8: latency average = 106.556 ms 5 ^ 8: latency average = 734.834 ms 6 ^ 8: latency average = 3640.507 ms 7 ^ 8: latency average = 14470.199 ms tiebreaker + incr sort hack: 4 ^ 8: latency average = 93.998 ms 5 ^ 8: latency average = 740.120 ms 6 ^ 8: latency average = 3715.942 ms 7 ^ 8: latency average = 14749.323 ms And as far as this: > I suspect that I fat-fingered work_mem yesterday, so next I'll pick a badly-performing mod like 32, then range over work_mem and see if that explains anything, especially whether L3 effects are in fact more important in this workload. Attached is a script and image for fixing the input at random / mod32 and varying work_mem. There is not a whole lot of variation here: pushdown regresses and the tiebreaker patch only helped marginally. I'm still not sure why the results from yesterday looked better than today. -- John Naylor EDB: http://www.enterprisedb.com
bench_windowsort_workmem-20230215.sh
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