Re: POC: converting Lists into arrays

Andres Freund <andres(at)anarazel(dot)de> writes:
> I don't buy this. I think e.g. redisgning the way we represent
> targetlists would be good (it's e.g. insane that we recompute
> descriptors out of them all the time), and would reduce their allocator
> costs.

Maybe we're not on the same page here, but it seems to me that that'd be
addressable with pretty localized changes (eg, adding more fields to
TargetEntry, or keeping a pre-instantiated output tupdesc in each Plan
node). But if the concern is about the amount of palloc bandwidth going
into List cells, we're not going to be able to improve that with localized
data structure changes; it'll take something like the patch I've proposed.

I *have* actually done some tests of the sort you proposed, driving
just the planner and not any of the rest of the system, but I still
didn't find much evidence of big wins. I find it interesting that
you get different results.

regards, tom lane