Re: v17 vs v16 performance comparison

Alexander Lakhin <exclusion(at)gmail(dot)com> writes:
> I've repeated the performance measurement for REL_17_STABLE (1e020258e)
> and REL_16_STABLE (6f6b0f193) and found several benchmarks where v16 is
> significantly better than v17. Please find attached an html table with
> all the benchmarking results.

Thanks for doing that!

I have no opinion about b7b0f3f27, but as far as this goes:

> But beside that, I've found a separate regression. Bisecting for this degradation:
> Best pg-src-17--.* worse than pg-src-16--.* by 105.0 percents (356.63 > 173.96): s64da_tpcds.query95
> Average pg-src-17--.* worse than pg-src-16--.* by 105.2 percents (357.79 > 174.38): s64da_tpcds.query95
> pointed at f7816aec2.

I'm not terribly concerned about that. The nature of planner changes
like that is that some queries will get worse and some better, because
the statistics and cost estimates we're dealing with are not perfect.
It is probably worth drilling down into that test case to understand
where the planner is going wrong, with an eye to future improvements;
but I doubt it's something we need to address for v17.

regards, tom lane