Re: First draft of the PG 15 release notes (sorting)

On Wed, May 11, 2022 at 12:39:41PM +1200, David Rowley wrote:
> I think the sort improvements done in v15 are worth a mention under
> General Performance. The commits for this were 91e9e89dc, 40af10b57
> and 697492434. I've been running a few benchmarks between v14 and v15
> over the past few days and a fairly average case speedup is about 25%.
> but there are cases where I've seen up to 400%. I think the increase
> is to an extent that we maybe should have considered making tweaks in
> cost_tuplesort(). I saw some plans that ran in about 60% of the time
> by disabling Hash Agg and allowing Sort / Group Agg to do the work.

Is there any reason not to consider it now ? Either for v15 or v15+1.

I wonder if this is also relevant.

65014000b35 Replace polyphase merge algorithm with a simple balanced k-way merge.

--
Justin