Re: More speedups for tuple deformation

Hi,

I haven't yet looked at the new version of the patch, but I ran your benchmark
from upthread (fwiw, I removed the sleep 10 to reduce runtimes, the results
seem stable enough anyway) on two intel machines, as you mentioned that you
saw a lot variation in Azure.

For both I disabled turbo boost, cpu idling and pinned the backend to a single
CPU core.

There's a bit of noise on "awork3" (basically an editor and an idle browser
window), but everything is pinned to the other socket. "awork4" is entirely
idle.

Looks like overall the results are quite impressive! Some of the extra_cols=0
runs saphire rapids are a bit slower, but the losses are much smaller than the
gains in other cases.

I think it'd be good to add a few test cases of "incremental deforming" to the
benchmark. E.g. a qual that accesses column 10, but projection then deforms up
to 20. I'm a bit worried that e.g. the repeated first_null_attr()
computations could cause regressions.

Greetings,

Andres Freund