Jeff Davis <pgsql@j-davis.com> writes:
> What is your opinion about pessimizing the HashAgg disk costs (not
> affecting HashAgg plans expected to stay in memory)? Tomas Vondra
> presented some evidence that Sort had some better IO patterns in some
> cases that weren't easily reflected in a principled way in the cost
> model.
Hm, was that in some other thread? I didn't find any such info
in a quick look through this one.
> That would lessen the number of changed plans, but we could easily
> remove the pessimization without controversy later if it turned out to
> be unnecessary, or if we further optimize HashAgg IO.
Trying to improve our cost models under-the-hood seems like a
perfectly reasonable activity to me.
regards, tom lane