asolimando commented on PR #23975:
URL: https://github.com/apache/datafusion/pull/23975#issuecomment-5215808656

   > > An earlier set of four runs on the same machine produced -50.0% and 
-166.7%, so the tool reports both improvements and regressions where nothing 
changed (it failed AA testing, basically).
   > 
   > Is that too bad though? it's not like we are enforcing some specific 
benchmark numbers in the CI, users of the `dfbench statistics` cli can always 
apply some critical judgement when interpreting the stdout, same as with normal 
benchmarks, where there's always some small variability in two identical runs.
   > 
   > Do you foresee other places where reporting might be non-deterministic?
   > 
   > If It was just me using the tool, I think I could live with it being 
non-deterministic for certain operators, but in case other people don't, 
something that comes to mind is to add a new cli argument for skipping certain 
operators from the comparison. Something like: `--skip SortExec(TopK)`.
   
   To me it's still valuable as-is, as at the moment we don't have any easy way 
to assess improvements over statistics, as we have only a handful of CBO rules 
(`JoinSelection` notably) that can't move the needle much for benchmarks. If 
that's of any help, we could mark the benchmark as experimental for now, and 
follow-up on non-determinism (I couldn't think or find other similar problems 
apart from Sort+TopK I reported).
   
   Re. https://github.com/apache/datafusion/pull/23975#issuecomment-5214995064, 
during my investigation for the review, AI stumbled upon several long hanging 
fruits, and I could genuinely verify some after a cursory look, so I agree 
landing this benchmark would already have a tangible beneficial effect.


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