On Wed, Mar 19, 2025 at 3:31 PM Ashutosh Bapat <ashutosh.bapat....@gmail.com> wrote: > On Wed, Mar 19, 2025 at 8:22 AM Amit Langote <amitlangot...@gmail.com> wrote: > > Yes, those were with pwj=off. FTR, numbers I get with pwj=on. > > > > 3-way: > > > > nparts master patched %change > > 0 38.407 34.675 -9.717 > > 16 69.357 64.312 -7.274 > > 32 70.027 67.079 -4.210 > > 64 73.807 70.725 -4.176 > > 128 83.875 81.945 -2.301 > > 256 102.858 106.19 3.239 > > 512 181.95 180.891 -0.582 > > 1024 464.503 440.355 -5.199 > > > > 6-way: > > > > nparts master patched %change > > 0 64.411 67.175 4.291 > > 16 203.344 209.75 3.150 > > 32 296.952 300.966 1.352 > > 64 445.536 449.917 0.983 > > 128 805.103 781.892 -2.883 > > 256 1695.746 1574.346 -7.159 > > 512 4743.16 4010.196 -15.453 > > 1024 16772.454 12284.706 -26.757 > > > > So a bit less impressive than the improvements for pwj=off. Also, > > patch seems to make things worse for low partition counts (0-16) for > > 6-way joins, which I am not quite sure is within the noise range. > > Have you noticed that too and, if yes, do you know what might be > > causing it? > > I have observed similar things with lower numbers of partitions. In my > observation, such results have coincided with relatively large > variance. With 0 partitions there is no difference in the code > behaviour irrespective of pwj ON or Off. Hence we don't expect any > variation in the numbers you posted yesterday and today when nparts = > 0. But there it is. I have always observed that much variation in > planning time for one combination or the other. > > With 6 -way join there will be 6 * 5 - 5 derived clauses in one > equivalence class, That's close to 32, which is the threshold to start > using a hash table. So some slight perturbation is expected around > that threshold. But given that it's lower than 32, that shouldn't > apply here.
Ok, thanks for that analysis. I don't think there's anything about the patch that makes it particularly less suitable for pwj=on. I read patch 0002 in detail last week and wrote a follow-up patch (0003), mostly for cosmetic improvements, which I plan to squash into 0002. I’ve also revised the commit messages for 0001 and 0002. Let me know if that looks reasonable or if I’ve missed any credits. -- Thanks, Amit Langote
v2-0003-amit-delta.patch
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v2-0002-Make-derived-clause-lookup-in-EquivalenceClass-mo.patch
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v2-0001-Add-assertion-to-verify-derived-clause-has-consta.patch
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